Ham's Life

BLOG HAS MOVED

2010-07-19T14:25:00.000-07:00

This blog has moved to http://hamslife.com .

I also have lessons for technician class ham radio license at http://hamslife2.blogspot.com

Thank you

73

Bill WA6OHP

HETRODYNE, REGENERATIVE & SUPER REGENERATIVE HOW DO THEY DIFFER?

2008-02-08T13:26:00.000-08:00

The 03/23/2007 article I posted on this blog site titled “The Regenerative Receiver” prompted a comment with a question. The question follows: “one question i have is - are the following principals basically the same - how do they differ? Heterodyne Regenerative and Super Regenerative. I want to try to answer that question here because I must have left something ambiguous in that article.

The word “heterodyne” is derived from two Greek words; “hetro” which means different and “dyne” meaning power. By combining the two words we see that it latterly means a different power. A heterodyne is a signal which is produced by mixing two or more signals in a non linear device or to say it another way heterodyning is the process of mixing two or more signal frequencies to produce a different frequency signal. When two frequencies are mixed they actually produce two new frequencies. So if a 7.100 MHz signal was mixed with another signal having a frequency of 6.645 MHz it would produce an output of 455 KHz and another of 13.745 (the sum and the difference of the two frequencies). In that case, considering 455 KHz is a very common IF frequency, the 455 KHz signal would probably be the one desired and the 13.745 MHz signal would be filtered out.

The technique of heterodyning was developed by a Canadian inventor and engineer named Reginald Fessenden.

After the process of heterodyning was developed and understood the superhetrodyne receiver could be developed. Prior to the superhetrodyne receiver and after amplification was possible receivers had a series of RF amplifiers ahead of the detector. Each of these amplifiers had to be retuned when the receiver frequency was changed. The superhetrodyne receiver eliminated the need to have a series of RF amplifiers that had to be tuned separately. Normally there is one RF amplifier ahead of the mixer though there can be more and sometimes the mixer is the first stage. The input to the mixer is tuned and the frequency of the local oscillator which produces the signal to be mixed with the incoming frequency can be variable (in some cases the local oscillator is crystal controlled) so the output frequency always remains the same. Each RF amplifier, which is actually called Intermediate Frequency (IF) amplifier, can be tuned to the same frequency no matter what the input frequency is. Using an IF frequency allows the construction of more selective circuits. Fixed frequency filters can be easily added to the IF giving greater selectivity then possible with LC circuits.

Ease of tuning, improved gain, and increased selectivity are three advantages of the Superhetrodyne receiver. An other advantage was provided by the fixed If frequency being fed into the detector is it allows the signal of the IF to be mixed with the signal produced by the beat frequency oscillator (BFO) which makes receiving CW and SSB much easier (the BFO heterodynes the IF frequency down to audio frequencies).

Regeneration is a process where by some of the output signal of an amplifier is sent back, in phase, to the input. When the output of an amplifier is sent back to the input it is called feedback. When a sufficient amount of the output signal is sent back to the input in phase the amplifier will sustain its own signal producing process called oscillation. Feed back can be regenerative (positive feedback or in phase feedback) and degenerative (negative feedback or out of phase feedback).

As the article I mentioned above describes, the regenerative receiver used a small amount of positive feedback to improve the receivers amplification and its selectivity so one tube acting as the RF amplifier and detector worked very efficiently. When the feedback was increased to the point where it started to oscillate a signal was being produced which would mix with the incoming signal to produce a tone so a CW signal could be read.

A super-regenerative receiver is a regenerative receiver which uses a quenching frequency to prevent oscillation.

So I guess the answer to the question I was asked is heterodyne and regeneration are two different processes and regenerative and super-regenerative differ in that the latter uses a quenching frequency.
--------------------------------------------------------------------------------
I was a little surprised to see the comment posted yesterday because I didn’t know anyone was still reading this blog site. My new blog site http://hamslife.com has all of the same information I post on this site plus much more. Any who read this I would like to invite you to my new site.

THE CALIFORNIA HAM PLATES CONFUSION

2008-02-04T10:29:00.000-08:00

Recently I was driving my wife’s Toyota with license plate number “KI6YQ”. As far as I knew I was carefully observing the laws of the state of California but the red and blue lights of a local police car came on behind me and I pulled over.

With my driver’s license in my left hand which rested with my right hand on top of the steering wheel I waited until the officer approached the open window. His first words were not asking me for my license and registration but he asked me if my vehicle was properly registered. The officer said he was unable to find the license number in the data base when he ran it. I assured him it was properly registered and that he needed to look again under code H because it was a ham radio plate. This was not the first time I had run into this problem. The officer did not think that was the problem but apparently wondering why he could not find the plates in the data base he let me go.

Ham radio license plates have been issued in the state of California long before the personalized plates program was in existence. It was a lot of fun before the personalized plates because when those of us who had ham plates would purchase fuel, which in those days was pumped by an attendant, and the station attendant took the credit card to run the information he would walk to the front of the vehicle to get the license number, part of the required information. The looks on the faces of some of those attendants was worth the cost of the fuel, which by then was about 10 cents per gallon. I have even been asked if I worked for the government or if I was a CIA agent or something like that. Now with personalized plates those days are gone of course they would be gone in California anyway because we now pump our own fuel and run our own cards.

When the state of California started the personalized plates they were going to integrate the amateur radio plates into the program and charge extra then $25 a year for the privilege of having them. It was only because the amateurs were willing to protest and show the value of ham radio communications in times of emergency that the state relented and no extra charge would be imposed beyond a small retooling cost when the plates are first issued.

It seems recently hams who were applying for new call letter plates were being issued plates with an extra space in them appearing just after the number. For example my wife’s car would have been issued, if she was applying for a new plate, KI6 YQ instead of KI6YQ. Again protest was made.

It seems that the DMV had put a space in the data base so as to distinguish the amateur radio plates from the vanity plates and thus it was necessary to place the space on the plates to agree with the data base. This may have been the reason the officer pulled me over and could not find the plate in the data base because the vehicle’s plate did not have a space in it. These two classes of plates have existed for over 30 years with no problem so why now? The answer, as far as the DMV was concerned, was simple. If the hams would just change their plates to vanity plates and pay the yearly charge which is now over $40 a year we could have the plates without the space.

With some assistance from legislators the DMV has now said they will remove the space from both the data base and the new license plates being issued and thanks to hams who were willing to become involved the ham radio plates were saved again.

Could it be that the state was just trying to make a little extra money? How could I think such evil? They would never do something like that would they?

Closing note: This did not just affect the hams in California because I assure you every state in the Union was watching to see how it went. Every ham in the US with call letter plates could have been affected and as far as that goes every country where call plates are issued could have followed suit.

REVIEW: RAMSEY QAMP20

2008-01-12T15:54:00.000-08:00

Ramsey Electronics has several inexpensive easy to assemble electronic kits. Some are specifically amateur radio related and others are not. The QAMP20 is a 20 meter 20 watt linear amplifier. Being linear it will run CW, SSB, or AM. It can be driven with ½ to 2 watts with a power requirement of 12 VDC at 4 Amps.

Ramsey’s estimated assembly time is 4 hours for beginner, 2 hours for intermediate, and 1.5 hours for advanced builders. I did not time myself but I would say that their timing estimate is fairly accurate.

The instruction booklet, as with all their kits I have assembled so far, is very well done and can be followed by anyone even with no electronic knowledge.

Alignment is very easy. Basically it is just a matter of setting the bias.

The work horses of the amplifier are two P16NF06 MOSFET transistors. They are run in Push-Pull format so as to reduce potential second harmonic output. It has a 3 stage pi network low pass filter output to further reduce the harmonic output. The input and output to the transistor are both through ferrite wideband transformers.

The exciter input uses a T-R relay circuit which is operated by a simple diode detector to sense when RF is applied and a two transistors amplifier circuit to drive the relay. If the power switch is not on the relay will not actuate and thus the exciter can be run “bare foot” but when the power is on it will switch on as soon as the exciter is keyed.

When testing the QAMP20 I found that ½ watts in gave 5 watts out and 1 watt in gave 10 watts output. An IFR service monitor’s power meter was used for the test. The efficiency is about 30 to 35% which is about where a class AB amplifier should run.

Over all, with the exception of the plastic box to house the unit, I would give this unit a very high rating considering the cost.

--------------------------------------------------------------------------------

This amplifier is for sale on eBay: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=190189665379&ssPageName=STRK:MESE:IT&ih=009

I AM TALKING TO MY WIFE’S DOCTOR.

2007-12-21T11:40:00.000-08:00

The Coast Guard Cutter McLane had two transmitters on board for CW operations. The transmitter for 500 KHz was a TDE a big black box, max DC input power 125 watts, frequency range 300 KHz to 18 MHz, and had a VFO. We also had an AN/FRT23 for HF operation but it was crystal controlled. So the only transmitter that would allow ham radio operations was the TDE but I had been given direct orders from the XO not to use any of the ship’s transmitters for amateur radio purposes.
About 9 months after reporting aboard the McLane I was married and then about a year after that my oldest daughter was born. My wife was at that time WN5NEP and her doctor was W5MSQ.
The local ham radio club had a SSB net every Sunday afternoon on 80 Meters. One Sunday while I was on duty (that means staying aboard to protect the cutter while it is in port) I wanted to check into the net but using the TDE on CW was my only option. Even though I was on CW the net welcomed me in and after the net was over Doc (W5MSQ) and I shifted down to the CW portion of the band and had a lengthy QSO.
During our QSO the OD (officer of the day), a boatswain’s mate who knew nothing about radios, stopped by the radio room when he saw there was some activity. He asked me what I was doing.
I knew I was had. Violation of a direct order from the XO was sure to bring serious consequences. I may have gotten by with it if I told him I was testing out the transmitter but that would be a lie.
I looked up at him and simply said, “I am talking to my wife’s doctor.”
At that he started laughing so hard he could hardly contain himself. He walked off the bridge laughing and repeating, “I am talking to my wife’s doctor.”
He didn’t believe me, he didn’t tell anyone, and I didn’t get into trouble. That was the first and last time I used the ship’s transmitter for amateur radio use.
----------------------------------------------------------------------------------
See information on the McLane at http://www.silversides.org/mclane.html

For blog posts like this and more go to http://hamslife.com

B-52 COMMUNICATIONS IMPROVED BY HAM RADIO OPEARATORS

2007-12-07T17:03:00.000-08:00

In 1960 Single Side Band (SSB) signals could be heard on the ham bands but standard Amplitude Modulation (AM) was still the most popular mode of voice transmission. There were arguments as to the value of SSB over AM (SSB is a modified standard AM signal). Quality of the sound was one major objection to SSB while cost and complexity of equipment for transmission and reception was another. But change was, and still is, inevitable thus SSB quickly grew to the point where it became the normal and AM (sometimes called Ancient Modulation) became the rare mode of communications.

SSB was first introduced by John Renshaw Carson when he applied for paten on 1 December 1915. The first recorded used of SSB was by the telephone companies starting in the 1930’s as a means of multiplexing (using a single carrier or in this case single pair of wires to carry multiple information channels simultaneously) telephone lines. Using a pilot frequency a carrier was established for each channel and the Upper Side Band was used to transmit the communications in one direction while the Lower Side Band was used to transmit the information in the other direction.

After WWII amateur radio operators began to experiment with SSB on the air.

Up to 1950 the United States Air Force bombers carried a radio operator to maintain communications. This meant an extra person, thus that much less payload could be carried and extra fuel was needed. It also required the operator to receive a message and passing that information on to the pilot or other crew member for whom it was intended. The reverse was also true; the radio operator took the message and passed it on to its intended recipient’s operator. With the advent of the B52 jet bomber communication speed needed to increase to accommodate the increased speed of the aircraft’s movement. The middle man, the radio operator, became the target for elimination.

Two Generals in the United States Air Force, General Curtis E. LeMay W6EZV and Lt. General Francis H. Griswold K0DWC, addressed this problem by placing SSB amateur radio stations in two B52 bombers. By this they were able to prove the improved quality of long-range voice communications. High quality long distance voice communications allowed the crew to communicate directly without a radioman.

HOW MANY WRAPS BEFORE SOLDERING?

2007-11-29T15:28:00.000-08:00

October 4, 1957 was a day of well earned celebration in the Soviet Union for it was on that day they beat the United States in launching the first artificial satellite which they called "Спутник" (Sputnik) meaning "co-traveler", "traveling companion" or "satellite". This was the beginning of the “Space Race” which diverted some of the tension caused by the “Cold War.”

The United States was not able to successfully launch an artificial satellite until April 28, 1958. Prior to that successful launch the US had blown up two rockets on the launch pad. After that success they blew up four more rockets before finally again succeeding. ]

NASA, which came into existence in 1958, found the reason for the failure was do to not bad engineering but was the result of poor quality control especially in the area of soldering. NASA developed some changes in soldering technique. These changes not only virtually eliminated solder connection failure but also reduced the weight of the vehicle and payload.

Prior to the new standards of soldering a wire being soldered to a terminal was wrapped at least a full 365 degrees and most of the times two or three times then it was soldered. NASA standards said a wrap was to be no more then 90 degrees.

Another change NASA instituted was the way a PC board was loaded. Up to that time when a component was placed in a PC board the leads were bent and run through the board then bent again to run along the trace then it was trimmed and soldered. NASA standards called for the leads to be bent at least the diameter of the lead away from the component, inserted into the lead holes with the leads sticking straight out, and then the leads were cut almost flush with the board trace and soldered.

The main complaint with the NASA standards of soldering was if a solder connection was missed that component could fall out, a wire could fall off the connector, or it would fail when tested especially if vibrated during test. The funny thing about that argument is it is exactly right and that is why it makes it the best way to do the job. Using the old standards a missed solder connection may test well when first made but it is a failure waiting to happen as the contact ages. If a component falls out or if the wire drops off the connection so it is easy to see before testing repair can be made at that time. If the unit is vibrated during testing so missed solder connections will fail at that point it will prevent failure later during more critical operating conditions.

When constructing a project carefully clean the surface of each solder joint with a pencil eraser. A little rosin flux can be added to the surfaces to be soldered to prevent oxidation and help conduct heat. Use sufficient heat to melt the solder quickly and melt the solder on the contact surfaces and not on the soldering iron. Use very little solder. Clean flux residue with denatured alcohol using an acid brush while the it is still hot but the solder is solid.

By following these few soldering tips your completed project should give you many years of failure free service. Another added advantage is defective components can be removed with little effort so they can be replaced.
------------------------------------------------------------------------------

http://hamslife.com/ is now up and running with new features coming. If you have been reading this blog and enjoying the articles you can see the same articles and more on http://hamslife.com/

CQ

2007-11-23T11:33:00.000-08:00

CQ CQ CQ this is WA6OHP Whiskey Alpha Six Oscar Hotel Papa WA6OHP. Over and over that phrase would be repeated in my home and while we lived in a mobile home (1965 to 1969) that place in the home was the living room. My oldest daughter knew the phrase well at two years of age and when we got a cat she felt the appropriate name for her would be CQ and that it was for as long as we had that cat.

Did you ever wonder how those two letters were chosen to mean ‘calling any station’?

Most, if not all, who are reading this post know it originated with Morse code and was brought over into voice when that mode became available. Before SOS was used CQD was the recognized wireless call for distress. The Titanic transmitted its distress message by calling CQD DE MGY (the Titanic’s call sign was MGY) though it shouldn’t have because by 1908 SOS was the standard international distress call and the Titanic sank in 1912. DE was used to mean “this is” because the French word “de” means “from or this is” and in the United Kingdom French was, and still is, the official language for international postal service. The postal service in the UK and many other European countries operated the telegraph offices. Remember most of the wireless telegraph operators at that time were former wire telegraphers.

The French word which is equivalent to the English ‘safety’ is sécurité. When the two letters CQ are spoken they sound similar the first two syllables in sécurité. CQ was first used by the United Kingdom landline telegraphers as a telegraph shorthand to mean “pay attention everyone I have something important to say to all.”

Operators from the United States and some other English speaking countries thought it meant “seek you” and there were some a few who thought CQD meant ‘come quickly distress’ but the European operators knew what it really meant. 1912 CQ meaning “all stations” became internationally accepted.

While CQ is inappropriate to use on a repeater it still can be used in other applications. There is an accepted procedure when calling CQ. Calling CQ on and on 10 to 20 times before giving the appropriate call sign is not that accepted procedure.

Normally it is advised to call CQ three times followed by giving your call sign three times and then repeat this two more times. The opening line of this post illustrates this when using voice communications. By following this procedure it gives the opportunity for stations tuning the band looking for a QSO to find you, set their equipment on your frequency in preparation to answer. Long drawn out CQ calls will sometimes result in stations leaving and looking for someone else who is not quite as long winded.

The three CQ followed by three times giving the call sign all being repeated two more times is not a set in stone practice but in most instances is recommended. Sometimes it might be best to abbreviate this by not repeating the whole thing three times.
------------------------------------------------------------------------------

http://hamslife.com/ is now up and running with new features coming. If you have been reading this blog and enjoying the articles you can see the same articles and more on http://hamslife.com/

HAM RADIO PARTICIPATION IN COMMUNITY EVENTS

2007-11-09T10:28:00.000-08:00

The ELEVENTH hour of the ELEVENTH day of the ELEVENTH month is a day of great significance in the United States of America (and I am sure many other countries but I can only speak for my own). It was on that hour, day, of month in 1918 that World War I came to an end and thus it was celebrated in the USA as Armistice .Day for many years as a day of remembrance of all who participated in that war. It is now known as Veteran’s Day. On this day there will be parades which provide opportunity for ham radio operators to provide a service to their community.

If you have never been involved in a parade then you probably have no idea how difficult it is to coordinate several different groups trying to make it all come off as a single event.

It might be like this a scout troop will be carrying the colors to lead the parade and they are to form together on J street with the horses just behind them. The colors guard is leave their position starting parade at the conclusion of the opening ceremonies (singing of national anthem, prayer, opening greetings from dignitary, and what ever else might be planned). The troop is 4 blocks away from where these events are happening so how will they know exactly when to step out and start the parade? It can be done without ham radio and has been done thousands of times but it is made easy with ham radio. A ham radio operator at the judge’s stand will tell another operator with the scout troupe to start lead out; meanwhile all other participating groups will know the parade has started, because the ham operator nearest their location will let them know, riders can get into position, band members can pick up their instruments and so on. If there is an emergency or breakdowns, and frequently at parades there are, assistance can be summoned immediately. There is always that participant who can not find his or her group; when they see someone with a radio they know there is help and sure enough there is. The call goes out asking where such and such a group is and the answer will soon come back and allow Bo Peep to find her sheep or what ever.

The above illustrates a few of the many benefits ham radio can provide for a parade. Have you ever watched the Rose Bowl Parade? As far as I know it is still true but I do know for many years it has been coordinated by ham radio.

Parades are one of the many types of community events where ham radio can help it run smother. Usually the ones who are doing the work trying to organize the events won’t think of ham radio if they have never been involved in an event where the assistance of ham operators was used. That is why it is important for the ham radio operators find these people long before the event is to take place and offer help. Sometimes it may take some persuading to show how ham radio can help but they will thank you later.

There are also many side benefits to this type of activity. It is fun, it will strengthen a club, it shows the community the value of ham radio, it helps bring new hams in from those observing, and it helps prepare the amateur participants to work together with other hams and non hams in the type of communications similar to that used during emergency operations.

---------------------------------------------------------------------
http://hamslife.com/ is now up and running with new features coming. If you have been reading this blog and enjoying the articles you can see the same articles and more on http://hamslife.com/

AMPLIFIER’S FLYWHEEL

2007-10-31T16:29:00.001-07:00

As I said in the article on classes on amplifiers the class C amplifying device (tube/transistor) only conducts during a small portion of the cycle yet the output is a sign wave. This accomplished by the “flywheel effect” of a tuned circuit.

Most people understand that the flywheel is a heavy wheel that uses its centrifugal force to swing a piston driven engine around so each piston will return into position and be ready for the power stroke again. The tuned circuit responds in a similar manner electronically.

A coil will store power in its magnetic lines of force. When the power is removed these lines of force will collapse back into the coil thus generating a voltage in the opposite direction as that which was applied. A capacitor also stores energy and when the circuit is completed between the terminals it will produce a current opposite to that which flowed during its charging. If a DC voltage is placed on a coil with zero resistance, no such coil exists, the instantaneous voltage will be equal to the source and the current flow will be zero. As the magnetic lines build the voltage will drop and the current will increase until the voltage is zero and the current is at the maximum level the source will allow. As the capacitor charges the voltage will go up until it reaches the value of the source and the current will drop to zero.

When AC is applied to the capacitor it will start to charge as the current starts to flow in one direction in one direction and then will start to discharge after the voltage peak starts back down towards zero. It will do the same on the other side of the AC wave form. This action will cause the current to be limited in a fashion similar to resistance except resistance results in power loss due to its generation of heat but this action of the capacitor, called capacitive reactance, does not produce heat. The larger the capacitance of a capacitor the smaller the reactance will be.

Considering the reaction of the coil, also known as an inductor, it should be easy to see that there would be an opposite reaction to the AC and this is known as inductive reactance.

Reactance, like resistance, is measured in ohms. When the inductive reactance and the capacitive reactance are equal the coil will discharge into the capacitor and when the clasping inductive field and the charging capacitor voltage are equal the current will cease to flow and the capacitor will discharge back through the coil. If there was no resistance and if no energy was radiated this action would continue on indefinitely but there is resistance and energy is radiated so the process dies out. If the output from the amplifying device continues to supply energy then the action can be sustained. This action is called the flywheel effect and it is how a class C amplifier can put out a sign wave.

If the tuned circuit are resonate at a multiple (harmonic) of the frequency being injected into the amplifier the flywheel effect will continue between the pulses then will be reenergizes on the next pulse. For example if the input circuit is tuned to 2 MHz the output circuit is tuned to 4 MHz spikes from the amplifying device’s output will be every other cycle and the amplifier’s output will be 4 MHz.

If the output is fed back to the input when power is placed on the circuit the tuned circuit will start vibrating and if it is in phase then the output will support the input and the output will continue to keep the tuned circuit vibrating. The results will be an oscillator.

My wife says when people ask me what time it is I have the bad habit explaining how to build a watch. That is a little of what happened here. My original intent was to explain what a linear amplifier is but I guess I got carried away. I hope you enjoyed this explanation of how amplifiers work. If you have questions or comments please email me at wa6ohp@yahoo.com, use the words Ham's Life or just hamslife in the subject line or rejected as span and I will never see it. I need feedback so I know what people would like to see.

AMPLIFIER CLASSES

2007-10-31T16:21:00.000-07:00

If the title sounds like an invitation to go back to school you need to read last week’s blog which is right below this one.

As was explained last week, an amplifier that is added on between a transmitter and the antenna is not necessarily a linear amplifier. But there are a lot more amplifiers then just the ones added on after a transmitter to boost the power. Amplifiers are the basic building blocks of analog electronics.

As stated the class of amplifier is determined by its level of bias. The class A runs for 360º of every cycle. That is to say when a cycle starts from 0 then rises to the full plus voltage then drops back to 0 followed by its negative swing back to 0 is a full cycle and the class A amplifier is on with its output following through out the cycle. The class A is the most linear but is the least efficient of the classes of amplifiers.

Efficiency is defined as the percentage of power output (AC/RF) to DC power input. If you have an amplifier running on 100 volts with .1 amps DC then the amplifier is running with 10 watts input power. If a wattmeter is placed on the output of that amplifier reads 2.5 watts then that amplifier has 25% efficiency which is about the maximum efficiency possible with a class A amplifier.

The efficiency can be increased by moving the bias up to cutoff and thus driving the amplifier to class B. The class B amplifier runs for 180ºof every cycle. The active amplifying device (Tube or Transistor) is on just half the time and off half the time during any cycle. While the amplifier is linear as described in the last blog it will distort an audio signal because half of the cycle is cut off. To compensate for this two tubes or transistors work together in such a way that while one device is off the other is on thus completing the cycle at the output. This configuration is called push pull amplifiers. The efficiency of the class B amplifier is raised to about 50%. With no drive (input signal) the class B amplifier draws no current.

Because the active component is only operating 50% of the time it can run at higher power then it can in class A. Though vacuum tube is ancient history it is easier, at least for this author, to use it to compare thus the 6C4 vacuum tube characteristics will be used for illustration. The reason for using this tube is because it was a popular tube for use for both audio and RF and the needed information was readily available from the RCA Receiving Tube Manual. When run in class A configuration the maximum DC input, using the recommended 100 volts plate voltage, is 1.1 watts thus about .28 watts out. When used for class B operation it could be run at about 2.2 watts DC input, if the plate voltage remained at 100 volts (Class B in vacuum tube operation can be operated at a higher voltage which allowed it to be operated at an even higher power range.) The power output in class B would be about 1.1 watts (that is per tube so if push pull is used the output of the whole amplifier could be about 2.2 watts.) A significant increase over what it was capable of in class A.

The class AB amplifier must also be used in push pull when operated at audio frequencies. When driven with a small signal the AB amplifier, which is biased so the active device is not in cutoff, will actually run as a class A amplifier. When driven with a large enough signal this amplifier go beyond cutoff level thus running less the 360º but more then 180º.

The benefit of an AB configuration over an A is the AB has better efficiency (more then 25% but less then 50%). The little 6C4 would be able to have a DC input of about 1.65 watts with an output power per tube of about .58 watts.

Now the class C amplifier is, of course, biased well beyond cutoff so it operates for less then 180º. The operating time, though it varies some, is more in the range of 45º or less. If a signal is of to low a level it will not be sufficient to drive a class C amplifier so there will be no output, there will also be no DC current, until it is increased to a sufficient level to overcome the bias and drive the amplifier into conduction. In the case of the 6C4 it would only be conducting during the positive peaks of the signal. If the signal was small enough the output could be less then the input but as the signal is increased the output will increase in a non linear manor. If you double the drive the output will be well more then double. The class C amplifier will run at 75 to 90 percent efficiency. It can also be run at higher power so the 6C4, using the same voltage as before, can not run about 4 watts and have an output of above 3 watts. When operating in class C the 6C4 can safely be operated with 300 volts plate voltage at .025 amps which equals 7.5 watts DC input. That means it can have an output of around 6 watts or more.

A class C amplifier puts out a full sign wave even though it is only conducting on a single peak. While a vacuum tube that would be only on during the positive peaks transistors may turn of during the positive or the negative peak depending on the type of transistor. Next week’s blog will be on how the class C maintains a full 360º output.

WHAT IS A LINEAR AMPLIFIER?

2007-10-26T21:08:00.000-07:00

From just listening to QSO’s it seem that some hams don’t quite understand the real meaning of the term “linear amplifier.” It sounds like they think any amplifier that is added between the transmitter and the antenna is a linear amplifier. It is true that most of these amplifiers are linear but not all.

This article will be very elementary to some but not everybody is at the same level.

The word “linear” comes from the Latin word linearis, which means created by lines. A linear amplifier could be defined as an active electronic circuit that creates an output wave form that is an accurate reproduction of the input wave form that increases and decreases in direct proportions. The input lines and the output lines look the same though the output lines are larger and most of the times are 180° out of phase with the input lines. Thus if a linear amplifier has a 1 KHz sign wave input at .1 watt with an amplification factor of 100 then the output would be a 1 KHz sign wave at 10 watt times the efficiency factor (the percentage of output power to DC input power) of the amplifier. If the input is increased then the output will increase in direct proportion to the input (.12 watt in equals 12 watt out and .15 input equals 15 watts and so on with the efficiency factor not changing.)

The difference between a linear and a non linear amplifier is determined mostly by the class of amplifier being used.

There are 3 basic classes of amplifiers, the A, the B, and the C with a hybrid class called AB and the AB class is divided into two sub categories the AB1 and the AB2 amplifiers.

A class A amplifier is biased so it conducts 100% of the time. If an amp meter is placed in line with a class A amplifier’s output DC source it will remain constant no matter what the input, that is assuming it is not overdriven. This constant is true even if there is no input signal. The class A is the most linear but the least efficient of the amplifiers.

A class B amplifier is biased at cutoff so it is conducting 50% of the time. Thus with no signal the class B amplifier will draw no current. It can be used as a linear amplifier if used in push pull configuration for audio frequencies and single ended if used for RF. There is a significant increase in efficiency over a class A amplifier.

A class C amplifier is biased beyond cutoff. The class C amplifier like the class B amplifier will draw no current with no signal input but a class B will start to draw current as soon as a signal is applied and a class C will only start to draw current when the signal strength is sufficient to go beyond the bias level. The class C amplifier is not linear but is the highest in efficiency.

Linear amplifiers which are added after a transmitter are usually class AB which means they are biased below cutoff but will draw current when activated. The class AB amplifiers have good linearity at RF frequencies. When amplifying an AM or SSB signal a linear amplifier must be used or the audio will be distorted. When amplifying FM, CW, RTTY, or digitally modulated RF signals a class C amplifier can be used and will give the greatest efficiency. Thus many amplifiers sold to use on VHF FM radios are not linear and can not be used for SSB VHF transmission.

What percentage of efficiency do the different amplifiers have and why? This will be the discussion next week

DO LEAD-ACID BATTERIES REALLY NEED DISTILLED WATER?

2007-10-19T20:11:00.000-07:00

The days of having to run the engine of your vehicle just to keep the vacuum tubes filaments of your mobile unit from draining the battery dry are gone but the necessity of keeping the battery in good condition are not.

The oldest modern rechargeable battery is the lead-acid battery invented by French physicist Gaston Planté in 1859. Though it has been around for almost 150 years the lead-acid batteries still has a lot of advantages over other types of rechargeable batteries. They can be partially drained or fully drained and recharged over many times without losing their ability to go through the cycle again. This is why they are still the preferred battery to use in the automobile. You start your car and the battery is partially drained by the starter current. When the engine is running the charging system rebuilds the charge and maintains it.

Other rechargeable batteries ,nickel cadmium, nickel metal hydride, lithium ion, and lithium ion polymer , would cost a fortune if constructed to sufficient size to start the engine and they would not stand up to that constant small drain and recharge over and over like the lead-acid battery does. Other rechargeable battery only has so many charges whether it starts from fully drained or just a partial drain and then it just wont take much of a charge and must be replaced but the lead-acid battery doesn’t seem to care how many times it is charged.

The lead-acid battery consists of lead (Pb) and lead Oxide (PbO2) plates submersed in a solution of water (63%) and sulfuric acid (37%). During discharge both electrodes surfaces turn into lead sulfate while the electrolyte loses some of its sulfuric acid to form the lead sulfate leaving a higher percentage of water in the solution. During this process electrolysis breaks down some of the water into hydrogen and oxygen an explosive mixture. That is why the lead acid battery must be operated with good ventilation. Evaporation also removes some of the water but the sulfuric acid does not evaporate significantly thus for all practical purposes only pure water will be lost during normal operation.

As the water level lowers it will need to be replaced. Pure water is lost pure water should be used to replace it. If there are impurities in the water they will change the chemical properties of the electrolyte and thus change the effectiveness of the battery. The sulfuric acid will breakdown many to the particles contained in impure water which will reduce the amount of acid contained in the electrolyte. It can also lead to an increase in resistance in the battery decreasing its performance and increasing its temperature during operation. Increased temperature increases the rate of evaporation which increases the frequency of necessary water replacement which, if pure water is not used, increases the resistance.

Replacing the water with distilled water is the only way to be assured that the chemical properties of the electrolyte will remain constant.

I strongly recommend that when you need to replace the water in your battery use distilled water which you have purchased and you know is distilled and add the water yourself or allow someone you trust to replace it for you. Almost every mechanic, service station attendant, or oil change specialist will replace the battery water with tap water because they either do not understand the importance or they don’t care and they want to save the pennies it costs for distilled water.

The effects of impure water will probably not be immediately noticeable but it will reduce the life and efficiency of the battery. When a lead-acid battery is properly maintained they will normally give you a warning when they are wearing out but batteries that have not been maintained properly more times then not will deteriorate more rapidly without warning leaving you stranded and having to call for assistance.

Should I tell the horror stories of jump starting? No I think I will save that for another time.

WHY IS RADIO TELEGRAPH CALLED CW?

2007-10-12T19:19:00.000-07:00

For years after becoming a ham I asked why CW was called CW. The answer was always the same, “CW means continuous wave” but it is not continuous because by nature Morse code is made up of broken carrier or wave. When I continued with this line of thought again I would get a single answer, “I don’t know why.” Oh if I had just talked to a ham who had been one for long enough to have used a Spark Gap transmitter I would have received my answer.

The first wireless transmitters were basically nothing more then a voltage source, a coil, an arc or spark gap, a key, an antenna, and a ground. The coil was frequently a spark coil from a model T Ford. The transmitted signal was over the whole RF spectrum. Later tuned circuits were added which suppressed the RF signals generated above and below a given wave length but the output was still a very wide portion of the band.

Another problem with the Spark Gap transmitter was the signal would dampen out. The signal could not be sustained for a long period and thus the spark must be continuously interrupted and restarted. This meant a lot of noise but that was good because the receivers were only passive devices. They had no amplification just a detector and those early detectors were not all that efficient. Certainly they did not have a bfo but with the white sound produced along with the interrupt/restart frequency there was a sufficient noise in the signal to copy.

After Lee de Forest added a grid to the Fleming valve, now called vacuum tube diode, in 1906 he found it could be used to amplify a signal. This allowed the construction of the regenerative receiver and soon the audion, the name de Forest gave his triode, was also used to as an oscillator to generate the transmitted signal. The first ham stations using this new form of generating and detecting an RF signal usually consisted of a single audion being used as both the transmitter and the regenerative receiver.

The definition for Continuous Wave is a single frequency sustained at a constant level. If a carrier is modulated it will contain sidebands and in the case of FM not only sidebands but also the frequency of the carrier itself changes. Thus to qualify as CW it must be unmodulated. CW was also known as "undamped waves", to distinguish damped wave generated by the Spark Gap transmission.

There were a few hams that experimented with trying to modulate spark gap transmitters but for the most part all wireless communications were by Mores Code.

Now the continuous wave could be sent but it contained no intelligence. To use it for communications it had to be interrupted into dots and dashes thus the true name for this communications was actually Interrupted Continuous Wave or ICW but the I was dropped and it became just CW, the necessity for the keying was understood.

There was a period of time where there were both CW and Spark Gap signals on the air. Those using Spark Gap usually had passive detectors and thus were unable to read the CW signals so amplitude modulation was added making it Modulated Interrupted Continuous Wave or IMCW which was shortened to MCW.

Now if someone asks you why radio Morse code is called CW you can tell them it is short for ICW.

Added Note:
I am planning to change this site to http://www.hamslife.com and include some extra features with it. I will continue to run this site for a while after I open the new one but in time this site will disappear.

CALL SIGN LICENSE PLATES AND BIG ANTENNAS

2007-10-05T11:29:00.000-07:00

Last week I was in Florida. That state has more different license plates then any other state I know but all the while I was there I did not see one ham radio license plate. Do they have call sign plates?

Contemplating this and searching for call plates reminded me of the days gone by.

In 1962 when I got my first car there were no vanity license plates and the California Highway Patrol used a frequency somewhere near the 160 meter band. There were only the standard format for license plates and when anyone saw a big antenna on a vehicle not marked CHP they thought it must be some type of government vehicle.

It was fun then because service stations were “service” stations not just a place to get gas (Oregon residents know what I mean because they still have service stations). After the attendant filled up the tank and checked the oil and water they would take the credit card and fill out the information. Part of that information included the license plate number. The look on their faces when they would see that plate number and then look at the big antenna was a site to see. Frequently they would ask if I was FBI or something. I finally found it was easier to say, “that’s classified information” rather then try to explain and it was more fun too.

The best one I can remember though was when I applied for my call letter plates. I was in the Coast Guard then and stationed in Brownsville, Texas. My car was in Colusa, California so after I got married my new wife and I went to California to take the car to Texas. When it came time I had to leave my new license plates had not arrived and the old ones had been turned into the DMV so the car only had a small red sticker showing it was registered.

We were driving along a long straight section of road through south eastern Colorado doing an excess of 80 miles per hour. My big old Webster Bandspander leaning back at quite an angle behind me when I saw a state police car come on from a side road and follow me. There were two officers in the vehicle and they followed me for a mile or two looking me over. Then they passed me, I looked at them and they looked at me all the while I kept my speed because I knew they knew how fast I was going and if I showed fear I would have been had. Then they drove in front of me with the officer on the passenger side turned around looking us over. They took the next side road and that was the last I saw of them.

Oh to have been the proverbial fly on the wall inside that police car! I can only imagine what might have been said. It may have gone something like this; after seeing that 59 Ford Fairlane 500 flying down the road with that big antenna, no license plate, and no apparent concern at their presence one officer asked the other, “what are they?” The other officer answered, “I don’t know and I don’t want to find out.”

Maybe they didn’t say that I don’t know but I do know I was a fast driver in those days even after I got my plates and the only time I was stopped was when I drove by a parked police car (I was not speeding) after I had installed a Heathkit Twoer. They followed me for a short while then pulled me over. One officer came up on one side of the car and the other came up the other side of the car. Both had a hand on their holstered firearm and the other hand on our vehicle door. They questioned me at length about who we were and what those radios were. It took me years to finally figure out why they stopped me. The Twoer has a supper regenerative receiver which radiates over a wide band. When I passed by and while they following close behind me it would open the squelch on their VHF police radio. That was one time when it was not fun.

SPECIAL EVENT STATIONS UNITED STATES COAST GUARD AUXILIARY

2007-09-24T10:55:00.000-07:00

The United States Coast Guard Auxiliary has been in existence for 68 years. The Auxiliary is a voluntary support team of the Coast Guard and assists the Coast Guard in all non military or police activity. Because most of the readers of this blog are ham radio operators or those who are interested in becoming ham radio operators it might stand to reason that many of the readers are like me; more interested in radio communications then in boating.

I joined the CG Auxiliary last year because they are looking for radio operators to assist in Coast Guard communications. A ham radio license is not required to join the USCG Auxiliary or to participate in the radio communications program but it is a natural fit. After saying that it would seem almost unnecessary to say but to avoid any confusion I am going to say it, class of license does not matter, all hams are welcome.

To promote this endeavor there will be a special evens day commemorating the 68 years of the Auxiliary’s service in saving lives. There will special event 1X1 stations operating such as K3G, N4C, and W8E. QSL will be sent is a S.A.S.E. is supplied. For more information go to: http://cgaux7.org/articles_dso-cm.asp
(If there are any questions or comments I will not be able to respond until after October 3 because I will be out of town.)

@ IN CODE

2007-09-21T12:36:00.000-07:00

With the advent of email the @ sign has gained popularity. It is now as well recognized as the & sign.

The “American Morse”, also known as “Railroad Morse”, had a character for & which has been used by amateur radio operators most of whom did not know they were using an “American Morse” character. Because the modern amateur radio operator uses “International Morse” which has a different timing arrangement then “American Morse” the letters e and s are used to make up the & sign. So when es is sent it is recognized as “and” but it really is the & sign.

(The original character makeup for & was not es but a dit with a slightly less time then that used between letters followed by dididit.)

Because the @ is used in email addresses and there was no code character for @ email addresses were difficult to exchange via CW. This problem was addressed by the ITU-R.

On May 24, 1844 the first transmission of a message by telegraph to be publicly observed was sent so it was on this date 160 years later (2004) the Radio Communication Bureau of the International Telecommunications Union (ITU-R) formally added the @ (which they called “commercial at” or “commat” for short) to its list of Morse characters. The new character is AC (Underscore means it is not two characters but all sent together as one) so it is sent as didadadidadit (• — — • — •).

The ITU-R is the same group that required amateur radio operators to demonstrate an ability to send and receive “International Morse” until they dropped that requirement on an international level in 2003. Think about it!

The @ sign is the first new character to be officially added to the Morse character set sense World War I. The information on what that character added during WWI was or its exact date of its addition seems to have been lost.

The problem now is to get the sign into common use so when sent other hams will be able to understand. We need to spread the word to others and use the character on the air.

History of the @ sign:

The origin of the @ sign has been lost to antiquity but it was known to be used by scribes to shorten the Latin word “ad” (at, to, or toward) as early as the 6th or 7th centuries.

The symbol can be found on 14th and 15th century clay pottery which were used to hold grain or wine and seems to have some connection to the measure or quantity it contained. Later it came to mean “at the price of”. Underwood added it to the 1885 typewriter keyboard.

The use of use of @ as part of the email address is credited to computer engineer Ray Tomlinson who in 1971 used it to separate the name of the intended recipient from their location with a character that would not appear in either name.

AMATEURS DEVELOPED TELEVISION

2007-09-15T09:26:00.000-07:00

Most people who are not ham radio operators are completely suppressed when you tell them that there are amateur radio television stations. People do not know how much the amateur radio community has added to the advancement of the art of radio.

On July 2, 1928 the FCC authorized C. F. Jenkins W3XK in Wheaton, Maryland to broadcast the first television signals. For the first eighteen months these were only silhouette images from motion picture films but it was a start.

W2XB started broadcasting the first regular schedule television transmissions on July 21, 1931. W6XAO in Los Angeles went on the air on December 1931 transmitting images every day except Sundays and holidays. W6XAO continued the broadcasting for several years.

While commercial broadcasters saw the potential in broadcasting radio programs on the AM bands it was not until after World War II that commercial television really began to catch on.

The average person not acquainted with the amateur community does not know this because we, as hams, do not tell them. It is interesting that for so many years they have complained about hams interfering with their television programs and had not been for the efforts of some ham radio operators it is possible that they would not have television programs to watch.

SOMEBODY GAVE ME A HORSE

2007-09-07T14:57:00.000-07:00

Someone left a comment last week. Unfortunately I had a Trojan horse running around in my computer and doing all kinds of damage. When I tried to open the comment to read it the whole comment was immediately deleted. I think I got rid of the problem but the comment is still lost. Please if the writer of that comment would restate what was said I would really appreciate it. I am sorry about the inconvenience.

This week’s post is going to be short because though I believe I have destroyed all the riders inside the horse and burned the horse itself I am now in the process of repairing all the damage caused by the attack. I was going to launch my Technician Class training project on http://hamslife2.blogspot.com on Tuesday but the invasion has put me behind on that endeavor.

Between now and next post does anyone know of some good ham radio blogs? I would like to add some links if anyone is interested.

Until next time.

73

IS IT TIME TO MAKE CHANGES IN THE QUESTION POOL?

2007-08-31T15:25:00.000-07:00

Over the past few weeks I have been working from early in the morning to late at night trying to put a program together that will help would be hams to get their license. The idea is to give them a new lesson each day Monday through Saturday with a refresher quiz on Sunday. This has caused me to carefully analyze and provide information on each question in the question pool.

Most of the questions are good questions but there a few that I personally feel should be removed or restated to improve the quality of the pool. I know it took a lot of work to put this together and we are never going to get 100% agreement on whether or not some questions is appropriate.

Just correcting grammatical errors would be an improvement.

Yes I know that statement could be applied to my own writings but I don’t have a proof reader. There are some qualified readers who could study the pool just for the purpose of correcting these errors.

I am not pointing out specifics because I do not want to offend or condemn. All I am saying is I believe the pool could be improved. These questions are the gateway to ham radio and a gate should be functional and efficient for the purpose for which it was established.

If you know anyone interested in getting a technician license these lessons will start on 09/04/2007 on http://hamslife2.blogspot.com .

HAMS ARE A FRIENDLY BUNCH

2007-08-24T21:11:00.000-07:00

When I first got my license a frequent practice, one which I do not necessarily recommend today, was to knock on the door of a house which had an antenna farm that appeared to belong to a ham radio operator and ask if a ham lived there. I have had people knock on my door and I have knocked on the doors of others.

While in boot camp for the USCG there was another ham in my company. When we reached the point where we were allowed our first liberty we went together and started to walk the streets of Oakland looking for a ham radio antenna. We really did miss our radio stations. The only thing we found was a group of interested people who started to follow us. This greatly alarmed my friend and he suggested we get a bus quick and leave that part of town which we did.

I remember another incident that happened just a few months later. It was while attending Radio School in Groton Connecticut that I met a young lady from Coventry RI who became my XYL and still is. While we were dating we frequently passed by a fire station, I think it was in Cranston but I am not sure now. Next to that fire station was a house with one of the most beautiful antenna farms I had ever seen. I know at the other end of the coax that lead into that house was a ham radio operator and I so wanted to meet him. Dottie, now KI6YQ, was totally unacquainted with ham radio and when I mentioned going to the house to meet its occupant she was did not think that was a very good idea (an understatement).

I persuaded her to go with me and we, I should say I, knocked on the door. As I remember Dottie was a few steps behind me. I wish I could remember the name and call gentleman who greeted us at the door but that has been way too many years ago. He invited us into his home. Collins S line was what I expected to see connected to the coax that went up to those antennas and I was not disappointed.

We were greeted and treated like old long lost friends. Those were good days and I miss them.

SOLDER VS SOLDERLESS

2007-08-10T17:59:00.000-07:00

When the western United States was known as the Wild West the telegraph helped to tame it. Several thousand miles of wire was strung across this nation. Bad weather and bad men would break or cut these wires and it became the job of a lineman to go out and repair the downed line.

The Western Union splice, also known as the lineman’s splice, was the accepted way of repair. A Western Union splice is made by bringing the two ends of the broken single strand wire so that when they are crossed there is a few inches of wire between the cross point and the ends. Usually it meant adding a piece of new wire and making two splices so the repair could be made and the line would maintain proper tension. Telegraph wire was not insulated so the dirt and oxidation had to be cleaned. At the cross a few tight twists of the wire are made. The splice is completed by wrapping ends of the wires in a tight coil wrap over the other wire with four or five turns. Clip off the ends of the two wires sticking out as close as possible to the splice and bend them down into the turns so as to not leave a sharp barb. This can all be done with nothing more then a lineman’s pliers and a piece of small grit sandpaper or emery cloth.

The Western Union splice was designed to be a solderless connection and if done right it is a good connection without solder but most Western Union splices today are soldered. A proper non soldered Western Union splice will improve with age because of cold metal flow.

If solderless connectors, also known as crimp connectors, are to be used they can be a trouble free connection if they are done properly. That “if they are done properly” is where the rub comes in. The right tool and the right connector must be used to accomplish this trouble free connection.

In the 1980’s while working on the night shift for a two way radio company it was one of my duties to repair the radios and installations used in customers’ vehicles in the field. By doing this at night the job could be done without down time for that vehicle. There was one trucking company that had a lot of complaints about the quality of their radio communications but I could rarely find anything wrong with the radios. The owner was a real grouch and because all previous technicians found the same as I had he was just considered to be a complainer without a cause. It was only because he had such a large account we catered to him. Digging deeper into the problem I found almost every truck, over 100, had improperly installed solderless connectors used on the power system. Sometimes a piece of wire was spliced and then in a few inches another splice and maybe one to three more before it reached the radio. I found as many as four splices in six feet of wire and none of them made correctly.

When first installed these connectors seemed fine but after time oxidation and dirt made them intermittent. The solution to the problem was to replace all the wiring in the trucks when it was found to have such a problem. My employer did not believe the problem was real and accused me of wasting time; he didn’t seem to notice that the trucks I repaired were being removed from the list of complaints. That is when I started saving all the bad wires and each night before going home I tied them to the knob on his office door.

After this went on for a while he not only agreed with me but he also asked me to please stop tying wires to his door knob. I was also given the no extra pay position of training all the other technicians how to properly make crimp connections and the ordering of proper tools and supplied.

Just as soldering is an art so is crimping. Quality crimp connectors are more expensive but in the long run they can save a lot of money, a lesson I had to teach my former employer. The best crimp connectors are the seamless crimp which means the point where the wire goes into the connector and is crimped is a complete tube with no seam. There are also some which are made by bending a flat piece of metal into a tube shape. Sometimes the seam is welded. The welded seam is almost as good as the seamless but when crimping them look for the seam and crimp squarely on that seam. The non welded seam contacts make good fodder for the recycle bin.

Use a ratcheted crimp tool that is designed for that connector. This will force you to crimp to proper pressure. If you use the cheep stripper, cutter, and crimper be sure the two points designed to touch when the tool is fully closed is actually touching before you release the crimp tool. Do not use a dimple crimp tool on connectors that have insulation in fact it is probably best not to use un-insulated connectors or dimple crimpers at all. Make sure the wire gage is the right gage for that connecter.

Just as with the Western Union splice crimp splices will improve with age. I can personally testify that I have seen measurements of the resistance new solderless connections and compared them to the resistance of solderless connections that had been made several months earlier. The oldest connectors were the lowest in resistance. When testing solder connections they would start with less resistance then the solderless connecters but after time they would increase in resistance. There was actually a point of cross over where the crimp connector became lower in resistance then the soldered connector.

HOW MANY WRAPS?

2007-08-03T16:42:00.000-07:00

During the middle 1960s, while working as a technician for the United States Army, I was sent to soldering school to learn soldering techniques used by NASA at that time.

A decade prior to this the Unites States and Russia had been involved in what was called a space race. The United States was losing big time. While Russia was sending up orbiting satellites the Untied States was blowing up rockets on the launch pad. While researching the problem it was learned by NASA that one of the main reasons for their failures was poor solder connections. Out of this was born the NASA standards of soldering I was learning.

Upon returning to my job all excited about applying my new found skills I was informed by my supervisor that I was NOT to use these skills. I was to continue soldering the same way I had been soldering. (The U. S. tax dollar at waist.)

In soldering school we were taught to use to solder to hold a component but it had been the standards prior to that to wrap or bend the lead of a component so they would not fall off. The result of the old technique was sometimes connections did not get soldered and after time when the newness wore off and the oxidation and dirt wore on these became intermittent failures.

Sometimes while making a repair or building a kit or what ever a job you can be irrupted. Upon returning it may be hard to remember just where you were and thus a contact you started to do did not get soldered. If the component is left in such a way that any effort to move the unit will result in the component falling off upon returning it will be easy to find where you left off.

When soldering components to PC boards do not bend the leads so a portion will lay flat on the solder trace. Run the leads straight out the hole. Solder the lead and the PC board. Trim off the excess wire. Not only will this prevent forgetting to solder a component but you will thank yourself for this if and when you have to change a component.

If the lead comes straight through and is not bent all one has to do to remove that component is place a piece of solder wick over the end of the lead. Heat the wick until the solder melts then slide the iron up the wick which will draw the solder up. After doing this the component should be able to come right off the board and the board should not be damaged due to excess heat.

This technique, it the solder connection was done correctly, will be solid with no significant loss do to resistance. Solder is a good conductor and has sufficient tensile strength to hole the component securely.

THE SKILL OF SOLDERING

2007-07-28T22:33:00.000-07:00

If you have any hardware technical interest in ham radio then most likely you are acquainted with a soldering iron. Soldering is a real skill. As a professional communications radio technician the majority mobile radio failure was not the communications unit but the installation. Of these failures improper solder joints was usually the source of the failure.

The two most important elements in a good solder connection are heat and cleanliness. The melting temperature of tin is 449.47 degrees Fahrenheit (231.93 degrees Centigrade) and the melting point of lead is 621.5 °F (327.5 °C). So it would seem reasonable that the melting point of 60/40 solder must be somewhere between 449.47 °F and 621.5 °F but the actual temperature at which 60/40 solder becomes liquid is 370 °F. If you would like to know more about why this phenomenon happens you will have to ask a metallurgist, who, last I knew, would give an answer something like this, “we don’t know.”

When a solder connection is done properly the joint being soldered must reach a sufficient temperature to melt the solder and allow the solder to wet the metal being soldered. Wet means the solder penetrates a few layers deep into the molecules of the metal being soldered. If the solder does not wet the metal then a condition known as a “cold solder joint” occurs. While the “cold solder joint” may not exhibit a problem when first made it is a problem waiting to happen.

Besides insufficient heat not allowing solder to flow dirt and oxidation will also prevent proper wetting action. This is where flux comes in to play. Flux does not clean and should not be expected to. After cleaning the point to be soldered the flux will help to cover the metal to prevent oxygen from oxidizing and it will help break down the very thin layer of oxide that will build. The flux will also help in heat flow.

PROTECT YOUR EYES!

2007-07-20T20:29:00.000-07:00

More years ago then I would like to admit I was a civilian technician for the United States Army.

It was required that we wear the safety glasses they provided Now I had been soldering for several years and I did it with out wearing glasses and I never got hot solder in my eyes. Oh well rules are rules so when at work I wore them, while at work.

Shortly after acquiring this job with that strange requirement I purchased a kit from Heathkit. Some soldering required. You have probably already guessed what happened and to this day I am not sure how I flipped that piece of solder into my eye.

As ham radio operators many of us enjoy working on our equipment or building something that requires soldering. Just a little caution could save you from a lot of pain and maybe even sight in one of your eyes.

ANTENNA TUNERS ON COAX FED ANTENNAS.

2007-07-13T20:30:00.000-07:00

Many hams seem to believe that if they use an antenna tuner and keep the SWR at 1 to 1 they are radiating the maximum signal. The truth is that antenna tuners can be deceiving.

A more accurate term for what is usually called an antenna tuner is a transmatch. It matches the output of the transmitter, which is usually 50 ohm, to the feed line input and not to the antenna.

If the feed line, the antenna, and the transmitter output all have the same characteristic impedance then everything is matched and maximum energy transfer will be accomplished.

The main reason for a transmatch is to protect the transmitter from reflected signal and to reduce stray RF in the shack when the antenna is reactive or poor energy transfer to the load.

The only way the antenna can be tuned is to have the tuner at the antenna end of the coax instead of at the transmitter end. If a random wire or a long wire antenna system, they are different, is being used then the Antenna Tuner is truly an antenna tuner because it can adjust the electrical length of the antenna thus adjusting the resonant frequency and impedance of the antenna. The tuner becomes part of the antenna.

There are some considerations when using a transmatch. One is the feed line can not be used near its operating limits. If RG58 coax is being used it can be used up to 500 watts if the system is properly matched but if a transmatch is being used to adjust the SWR to the transmitter there are dangers of very high voltage peaks on the coax between the transmatch ant the antenna. This could result in a voltage breakdown of the coax insulator. Also the reflected energy can cause excessive heat which could melt the insulator.

It should also be remembered that maximum efficiency will not be obtained especially if there is a large SWR that needs to be tuned out.

Some hams will brag about the fact they have a wire antenna and have never had to use a transmatch and that is fine but most wire antennas will not operate over the whole 80 meter band with a safe SWR. If the desired is to operate the whole band using a transmatch is far better then burning out finals.

A NEGLECTED ANTENNA WITH POSSABILITIES.

2007-07-07T22:22:00.000-07:00

As a radio operator in the United States Coast Guard it became my lot to serve on the USCGS McLane out of Brownsville, Texas. The McLane was 125 feet long and 25 feet wide and operated on HF frequencies from 2 MHz to 32 MHz with 180 watts of CW power. While serving on the McLane we went as far south as the Yucatan Peninsula. During the time when we were underway we needed to maintain communications with the Coast Guard Radio New Orleans NMG which at times was close to 1500 miles away. This was very successfully done with one antenna called an H antenna.

The H antenna started at the yard arms down both sides of the ship to 10 foot support poles at the stern and there was a wire crossing a few feet from the mast thus connecting the two wires running from the yard arm. This antenna interested me so I studied it and fount that the two lines coming from the mast were insolated from the single line which ran from the port side of the stern up to the insolated support line from the yard arm across to the insolated support line from the starboard side and then down to the starboard stern of the ship. A single wire ran from the antenna down to an insolated feed through on the rear bulkhead which went into the radio room and thus connected to the transmitter. After drawing the antenna I realized that it was just an old off-center fed Windom antenna that was formed in a U shape.

The Windom was a common antenna in the 1930’s but it is not selective against spurious radiation thus with the advance of TV sets and thus TVI problems the Windom fell into disuse. While underway the McLane had no problem with TVI so the antenna worked very well.

The antenna requires a very good RF ground. This will not only improve the operation of the antenna system but it will also help prevent stray RF inside the shack while transmitting. One reason the antenna may have worked so well on the McLane was the ocean is the ultimate ground.

The antenna is a half wave dipole, that is half wave at the lowest frequency used, fed at the 300 Ω point (.34 of total length on one side and .66 of the total length from the other end.) with a single conductor or twin lead.

A Windom antenna is said to work on the fundamental frequency and the even harmonics so the 1.8 MHz antenna would work on 3.6 MHz, 7.2 MHz, 10.8 MHz, 14.4 MHz, 18 MHz, 21.6 MHz, 25.2 MHz, and 28.8 MHz. This would make it on or close to the 160, 80, 40, 30, 20, 17, 15, 12 and 10 meter bands. On this type of antenna the antenna tuner acts as a real antenna tuner, unlike that of a coax fed antenna, and can make up for the difference. The frequencies used by the McLane were not as close to the even harmonics of the lowest frequency used as the ham band frequencies are to 160 Meter.

Most modern HF transmitters have linear amplifiers for use with SSB. Linear amplifiers have a very low spurious output so if a low pass filter is used between the antenna tuner and the transmitter output there should be very little problem. Also most TV’s are now used on cable or dish which are not as susceptible to TVI as they were in the earlier day’s television sets which were attached to antennas on the roof of the house.

Many hams feel constrained when it comes to putting up antenna because of limited room but as described above a very effective antenna was used by the United States Coast Guard on the very very limited space of a 125’ ship. If you can put two poles on the roof of your house which are parallel to the back fence and run a single 260 feet long wire starting at your back yard fence up to one pole then over to the other pole and then down to the back fence again you should be able to put up an antenna which could be used on any desired frequency from 1.8 MHz to 30MHz.

BATTRIES, ARE THEY SAFE OR DANGEROUS?

2007-06-29T21:32:00.000-07:00

If they are handled properly batteries are quite safe but if abused they can cause painful injuries or death.

First the lead acid battery used in automobiles need to be handled with care as not to spill the electrolyte on your skin.

When the mobile ham station’s battery is found dead there are some important procedures to follow. First remove all rings and conducting wrist bands (watch, bracelet, etc.) because if they accidentally short across the battery they can become red hot almost instantly. Next remove the main fuse for the radio, which should be placed very close to the battery, voltage surge during jump starting can destroy radios; I know I have seen it many times on customers’ units. Observe polarity of the batteries not wire color connected to the battery because sometimes battery wires are changed and more attention is given to length of wire and not what polarity the red or black wire is on. Put on your safety glasses (don’t have any? You should have a pair to protect your eyes while soldering so it is worth buying them).

After connecting the two batteries let the dead battery charge for a little while before trying to start. If the engine does not turn over do not just assume the connections are not good it could be the starter is bad or there is another heavy drain on the system. To continue trying to start the vehicle and moving the clips to make a better contact if such a condition exists this can cause in the battery to over heat and explode which will send hot electrolyte all over. This one I had to learn the hard way. Fortunately, though I was leaning over the battery moving the clips, I was not seriously hurt. Acid did get on me but I was able to flush it off with cold water before it had time cause serious burns.

The next time I saw the results of miss treating a battery it was a Ni-Cad battery. I needed to charge a battery but did not have a proper charger so I used a variable voltage power supply and a milliamp meter and set what I thought was a safe charging current. This was left over night. When I returned to the shop the next day there was paper shreds scattered all over the office. Then I found some very small pieces of plastic. It was then I remembered the battery that had been charging but was no longer there where I left it. The only thing I could think at the time was, “I am sure glad I was not here when that went off.”

This one is not by personal experience but as a technician for a large cell phone company I have had to warn several customers of the danger of carrying batteries in their pockets. This practice could result in a very painful lesson. If keys or coins in the pocket short out the battery it could result in a very hot piece of metal in your pocket that can burn or even worse the battery could quickly overheat and explode like the above mentioned battery that was not properly charged.

TRANSMITTER SIGNAL INTERFERANCE WITH OTHER ELECTRONIC EQUIPMENT

2007-06-22T17:36:00.000-07:00

When a computer, CD player, or some other non-tuned electronic system is affected by a transmitter it is usually not the fault of the transmitter. The same can also be said with tuned devices such as AM/FM radios and Televisions but there is a possibility of a transmitter defect can sometimes be the cause of such interference. It has been the hams who have been receiving the criticism for this problem for years but the real culprits are the manufactures for not using proper shielding to prevent such a problem. But blaming the manufactures does not get to the real root of the problem because people want inexpensive items and so manufacturing must cut corners to reduce the cost.

If an older transmitter with a class C final is being used then a good low pass or band pass filter should be used because class C amplifiers are rich in harmonics. Most transmitters today are designed to run SSB which requires a linear output that by nature do not have the high level of harmonics. Modern FM and CW only transmitters would be the exception.

The first thing that should be done when encountering such a problem, and this should be done whether or not a problem is known to exist, is be sure your station has a proper earth grounded. The ground at the power plug, that would be the green wire or half round hole of the socket, and cold water pipes are not a proper earth grounds. That green wire runs all though the house and works fine for 60 Hz but they are long and thus can act as an antenna to RF signals. Metal cold water pipes have joint compound to prevent leakage which can act as an insulator and many modern houses are plumbed with plastic pipe.

After assuring the ground system is good a ferrite toroid can be added to the transmitter’s power cord. If the transmitter uses an internal power supply then this would be the AC power cord but if it uses an external power supply the toroid should be used on the cord between the power supply and the transmitter. The toroid should be placed as close to the transmitter as possible. If an external power amplifier is used to boost the power of the transmitter then it too should have a toroid installed.

The toroid will need to be large enough around to pass the plug through and to take several wraps of the cord. Some modern units have the toroids already used inside the unit which will eliminate the need to add them externally.

If the problem continues add a toroid to the power cord of the affected device and the cord to each peripheral device (speaker, monitor, printer, mouse, etc). The toroid should be placed as close to the affected unit as possible.

A high pass filter in the antenna system of a TV is sometimes helpful especially when it is working off an antenna rather then cable or dish.

The above instructions are for your own equipment. Be very careful about doing anything to a neighbor’s piece of equipment because if anything happens to that device they will probably blame you for the damage. A lot of times too when such devices are added people will say that it is just not as good as it was before.

CW IS OBSOLETE! OR IS IT?

2007-06-16T10:29:00.000-07:00

For years have been those who have been saying CW is obsolete. These same people were criticizing the FCC for continuing to require CW on the ham test. The FCC finally gave in and eliminated it. The most common complaint is that CW is slow but when handling messages two good CW operators can, with less power and greater accuracy, pass more traffic then can be passed by voice operators.

If it is possible to transmit a signal it is possible to send CW. If noise can be made or a light can be flashed intelligence can be sent using Morris code. But sending it is not enough if there is nobody listening, or in the case of light watching, who can understand it. It is like trying to talk to someone who is not able to see you and doesn’t understand a word of your language.

NASA is one of the most advanced organizations in the world when it comes to technology. There is an interesting statement on their children’s web site (http://www.nsa.gov/kids/games/gameMorse.htm) under “FUN FACTS” where it says, “The U. S. Space Shuttles have a tiny telegraph key on the digital control panel of their high-frequency radio in case of emergency.” If there is a key on the shuttle then there must be someone onboard that knows CW and there also must be someone with NASA on the ground who also knows CW.

If NASA thinks CW is still worthy to be uses as a backup communications system then shouldn’t we be just as convinced?

USING COAX VELOCITY FACTOR FOR ANTENNAS

2007-06-09T19:02:00.001-07:00

Last week’s post was about a phenomenon known as velocity factor which is in RF feed line. This velocity factor is important to know when cutting feed line in wave lengths.

This velocity factor can be used to shorten the physical length of an antenna. If you would like to put up a full half wave 3.6 MHz dipole antenna you will need 156 feet of space but you only need 92 feet 9 inches if you construct the antenna using coax with a velocity factor of.66.

The antenna is constructed by cutting 2 quarter wave pieces of coax (264/frequency in MHz X .66 = 1 Quarter Wave) with a velocity factor of .66 (RG-8 or RG-58 not foam). Short the center conductor to the shield on one end of each piece of coax and leave the other end open. Connect the center conductor at the open end of each piece of coax to the to the feed line’s shield and center conductor the same as you would connect two pieces of quarter wave single wire to the feed line. Place insulators on each end of the dipole antenna just as on any dipole antenna and run it up in the air. It may have to be trimmed a little. This can be done with any frequency antenna. A 1.9 MHz antenna can be constructed at 183 feet 5 inches.

FEED LINE IS MORE THAN JUST A CONDUCTOR

2007-05-25T20:49:00.000-07:00

It is just two pieces of wire running parallel from the transmitter, receiver, or both to the antenna. Or two conductors, one inside the other with insulation in between the two, that bridges the radio to the antenna. Feed line looks simple but just a little study in its functioning properties will reveal that it is anything but simple. We all know about the characteristic impedance and because of the DC resistance it has loss but most know little beyond that.

One principle that is important to understand is the velocity factor of feed line. If you are going to make a balun with coax or some other need to cut coax in accordance to wave length you are going to need to know the velocity factor. If the formula 468/Frequency (MHz) = ½ wave length, as in cutting an antenna, the coax will be over the desired length because RF travels slower then it does in space or in an antenna conductor.

The proper formula is 491.5/F times VF (velocity factor) = ½ wave length in coax. The velocity factor for Belden 8259 RG-58A is 66% so a 20 meter quarter wave of this coax would be 491.5/14 = 35.11 feet 35.11 times .66 = 23.17 feet thus the ¼ wave length of that RG-58A coax is 11.85 feet or 11 feet 10 inches not 16 feet 6 inches.

CONFLICT BETWEEN HAM RADIO AND THE DEPARTMENT OF DEFENCE

2007-05-18T17:23:00.000-07:00

In 1904 Christian Hülsmeyer received a patent on a device that could detect ships in a dense fog. The device used radio wave reflections and was called a telemobiloscope. While it could detect the presence of a ship it was unable to determine the distance, course, speed, or any other pertinent information; it could only detect a presence of a ship.

By the 1930’s several countries, working on Telsa’s 1917 findings, to develop a system using reflected radio waves to fill in the gaps that the telemobiloscope left out. The British called it RDF (radio direction finding) but in 1941 the United States coined the term which would stick and become universally known as the RADAR (Radio Detection and Ranging). The development radar was highly escalated by World War II.

By 1950 the United States felt threatened by Russia and the Russians felt threatened by the United States thus was born the technology race for defense and offensive weapons by both countries to protect their country from the other. This became known as the Cold War.

The United States (I don’t know but I assume the Russians also) built a radar system that could detect hostel aircraft approaching its boarder. The system would have given plenty of warning against a bomber attack but when the Inter Continental Ballistic Missiles (ICBM) was developed along with submarine launched missiles and the system could not give sufficient warning against these menaces.

The United States developed a new system which would meet the new threats. It was called Precision Acquisition Vehicle Entry Phased Array Warning System (PAVE PAWS) [the real origin or real meaning of the PAVE portion of the acronym seems to have some questions].

Some of you may be wondering how ham radio fits in all of this. The United States Air Force suspect some of our 70 cm repeaters are with the PAVE PAWS system. There is an effort to have these repeater sites reduce their output power and there are hams who do not think they should have to do this.

I personally live under the shadow of the west coast PAVE PAWS site. On a clear day I can easily see it with the naked eye from my home. As a ham radio operator in the middle of the affected area I am one who will feel the direct impact of the outcome of this issue. But the results of this issue could have far grater consequences then just the hams in Northern California and a few New England states. This could directly affect the safety of everyone in the United States and many other countries who are depending on us for protection. It could also affect Canada and Mexico because nuclear fallout and biological agencies do not recognize country boundaries.

I for one firmly believe that if the 70 cm band operation or any other band operation is interfering with ours defense magnesium then those of us who live in the area of influence should be more then willing to discontinue operations on these frequencies. There could be very little time to react to an incoming missile and the Air Force needs all the advance warning possible. But on the other hand if the Air Force is not telling us the truth, which would not be the first time, then I would find it very irritating. Fortunately we have the ARRL looking out for our interest and lets hope the right solution if found.

SAVING HAM RADIO FOR FUTURE GENERATIONS

2007-05-11T23:05:00.000-07:00

Ham radio is not an inalienable right! The privileges of ham radio have been suspended in United States of America during war and they can be permanently taken away in the future if we do not continue to prove our value. Part 97.1 of the Federal Communications Commission describes the basis and purpose of Amateur Radio within its jurisdiction (USA). Other countries would most likely have a similar statement in their Amateur Radio service rules and regulations.

FCC 97.1 tells us that (I summaries) the purposes amateur radio is to provide noncommercial communications, particularly emergency communications. To advance radio art, advance skills in communications and technical phases of radio, provide an existing reservoir of trained radio operators, technicians, and electronics experts, and to enhance international goodwill. Though personal enjoyment is not prohibited it is not included in the purpose.

In times past it was fairly easy to prove the importance of ham radio to society but today with cell phones, advanced electronics, and internet service it is harder for non-hams to see the importance. Politicians are fed by the public so it is the public that must be convinced that we provide an important service to society. We know the value of our service but how can we show the public our importance?

To prove our importance to the public we must be in front of the public doing what we do best, communicating. One of the best ways of doing this is by finding local activities that can be enhanced by our presence. Parades provide an excellent chance to do this by helping keep all the groups coordinated through ham radio. Many other communities can also provide opportunity such as bike rides, trail hikes, street fairs, and any other activity where there may be the need of medical help, break down assistance, or coordination between people located in different areas of the activity.

Such activities not only helps us to be in the public eye but it also enhances our abilities and hone our skills so when the real emergency comes we ill be ready.

WHY IS THE SYMBLE FOR SOLID STATE DIODE BACKWARDS?

2007-05-05T16:59:00.000-07:00

Many people who start to learn electronics become confused. They are told that electrical current is composed of a flow of electrons and electrons flow from negative to positive which in itself sounds backwards. Then they are shown the symbol for a solid state diode and the arrow points towards the plus side to be forward biased.

The blame for this is usually placed on Benjamin Franklin who was the first person to start marking the charges as positive and negative in about 1750. Franklin had no way of measuring which way the current flowed so he had a 50/50 chance of being right but most people thinks he missed.

If the electron flow is the same as current flow and the diode symbol is an arrow then it would be pointing in the wrong direction. But if current flow and charge flow are the same thing then the negative charge is going towards the plus side and the plus charge is going towards the negative charge.

Frequently current flow is compared to water flow with the source of the water being the negative side; the water is compared to electrons, and the drain as the positive terminal. The illustration is a good one but like any illustration it is not perfect. There is not a pile of electrons that start flowing down the conductor like water in a pipe. The excessive negative charge knocks an electron out of an atom. This leaves a positive charge to that atom so an electron enters to replace the missing electron. The electron that was knocked out will migrate towards the positive side and it will knock out another electron and replace it so current flow is a series of electrons being knocked out of orbit and being replaced by another. This action will cause the negative charge to move towards the positive terminal and a positive charge moves towards the negative terminal.

So if you consider the symbol of a diode to be an arrow pointing the direction of current flow then just remember it is pointing in the direction of the positive charge flow known as Conventional Current Flow. But if you look at it as a horn with electrons flowing out of it then you might be a little less confused.

DIODE DESIGNED TO ACT AS A VOLTAGE REGULATOR

2007-04-27T20:00:00.000-07:00

In the days of vacuum tubes gas filled tubes were used as voltage regulators and they were effective for the need of the time. A tube normally runs at a much higher voltage then a solid state device and at a much lower current to perform the same operation. The voltage regulator tubes did not have a filament so they were called cold cathode tubes. The regulator tube was connected in series with a current limiting resistor and the two shunted the unregulated voltage. The 0A2 was one very common regulator tube. The 0A2 required an unregulated voltage of at least 180 volts. The result was a 150 volt drop between the plate and the cathode of the tube. The cathode would normally run directly to chassis ground and the +150 regulated voltage was picked off between the plate of the tube and the current limiting resistor.

GAS FILLED TUBE REGULATOR

ZENER DIODE REGULATOR

Because solid state devices normally require a much lower voltage then the 150 volts of the 0A2 or even the 90 volts of the 0B3 a lower voltage regulator is required. One way of doing this where a relatively small current is required is by using a zener diode. If you look at the schematic diagram of the tube regulator and the zener diode regulator they look much the same; a current limiting resistor in series with the diode but with the zener diode the plus voltage is taped off the cathode side of the diode.

The reason the zener diode is reverse biased is because as a regulator it works on the principal of the zener effect also sometimes called avalanche point. There is a subtle difference between zener point and avalanche point but it is too involved to be described here. The zener voltage is that voltage where the depletion region, that is the junction between the P and the N portion of the diode, is breached and current starts to flow. In most diodes when this region is reached the reverse current destroys the diode but in the case of a zener diode it is designed to work in this region up to a certain limit. The size of the resistor that is place in series with the diode is easily calculated. A zener diode is rated in voltage at which it works or its zener point and the maximum wattage it can sustain without destruction.

To calculate lets say we have a 12 volt unregulated source and we want a 6.1 volt regulated source. I used 6.1 because that is a common voltage in which the zener diode comes and it is close enough to 6 volt that it can be used in a most 6 volt application and for sake of simplicity I am going to use 12 volts and 6 volts as my two levels. The diode we will be using will be 1 watt. We know the voltage drop across the diode and the resistor will be 6 volts each. With the diode’s maximum power level being 1 watt and the current through the resistor being equal to the current through the diode plus the current through the load so the resistor should be rated over 1 watt. The maximum current that can flow through the diode is .167 amps (W/E=I) 1/6=.166666 which rounds up to .167. If the regulated voltage is being used to supply power for an oscillator which switched off and on for CW operation that draws .06 amps in key down and 0 amps in key up positions the resistor will have to be large enough to dissipate the key down power without allowing excess current through the diode in key up.

A good engineering practice is to run a device at about half of its maximum rating. Using this factor the maximum current that can pass through the diode is .0833 (Max. current = .167 amps times .5 equals .0833 amps). That means the resistor’s resistance can not less then 72 ohms (6V/.0833A=72.03 ohms). The voltage drop across both the diode and the resistor has to continue to be 6 volts so the current through the resistor must remain the same during both key up and key down. The current will have to be split between the load, the oscillator, and the diode which means the current through the diode will decrease by the amount of the load. The current through the resistor remains at .0833 amps when the .06 amp load is operating so the current through the diode will equal the total current through the resistor, .0833 amps, minus the current passing through the load, .06 amps thus when the oscillator is operating the current through the diode is .0233 amps (.0833 - .06 = .0233). This means the diode acts like a variable resistor so the total current through the resistor remains constant. When the load is on the diode increases its resistance and when the load is off the diode decreases its resistance so the voltage remains constant.

That was all easy but if the unregulated voltage is a vehicle battery then the voltage swings between 12 and 14.8 volts. To calculate this the extremes must be taken into consideration.

The voltage drop across the current limiting resistor this time will very because the voltage across the diode will remain at 6 volts When the unregulated voltage is 14.8 volts the drop across the resistor will be 8.8 volts. To limit the current to .0833 the resistor must be 106 ohm (8.8/.0833=105.642). When the unregulated voltage is at 12 volt the current trough the resistor will drop to .0566 amps which is insufficient to cover the necessary current of .06 amps necessary to run the oscillator. In this instant the maximum power rating of the zener diode can be raised this will allow the resistance of the current limiting resistor to be dropped sufficiently to provide the current necessary for the oscillator and regulator to operate.

There is another way to provide sufficient current even if the load requires well above the .06 amps but this requires some extra circuitry. It is done by controlling the output of a pass transistor with a Voltage Error Amplifier that compares the diode’s voltage drop and the pass transistor’s output voltage. By doing this the voltage drop across the zener diode and the voltage drop at the output of the pass transistor will remain the same.

DIODE DESIGNED TO ACT AS A CAPACITOR

2007-04-20T16:07:00.000-07:00

Last week’s post spoke of a diode that was popular in the sixties but has dropped in popularity. This week’s post will cover a diode that is being used in almost every new transmitter and receiver. The diode is a called a varicap diode, varactor diode or tuning diode. This diode is what allows the Phase Lock Loop synthesizer to change frequency.

A semiconductor diode is a piece of germanium or silicone with a very small amount of imperative inserted to form a molecular structure in which part has more free electrons called N material and an other part has a lack of free electrons called P material. The how and why this happens is beyond the scope of this post but to understand the varicap there needs to be a little understanding of the N and P reigns. Between the N and the P is a thin neutral reign which is called the junction. This junction prevents the flow of current until the voltage reaches the breakdown point which is about .2 volts for germanium and .6 volts for silicone when the diode is forward biased. If the diode is reverse biased then this gap becomes wider and will continue to become wider as the voltage is increased until the avalanche point is reached. Avalanche or zener voltage is that point where the reverse bias voltage breaks down the junction which usually results in destruction of the diode’s properties. There are some diodes designed to operate in the zener reign (zener diode).

A capacitor is simply two conductors separated by an insulator. The NP junction acts as the insulator between the N and the P reigns which acts as conductors and thus forms a capacitor. If reverse bias is applied the junction will become thicker causing the capacitance to decrease. If the capacitive reactance of the diode is in parallel or series with inductive reactance it will form a tuned circuit and by varying the reverse bias voltage the frequency of that tuned circuit can be changed.

A VFO can be constructed using the varactor diode as the capacitor but it is called a VCO (voltage controlled oscillator) instead of a VFO. The VCO can be stabilized to near crystal controlled stability. This is done by using a crystal controlled oscillator for a reference frequency and dividing the frequencies of both oscillators down digitally and feed the two new frequencies into a Phase Lock Loop (PLL) circuit with the output of the PLL going back to the VCO frequency controlling voltage.

A Phase Lock Loop (PLL) is a circuit that compares two frequencies and produces a DC voltage plus or minus when the two frequencies are not the same and a zero voltage when they are the same. If one of the oscillators (usually the crystal oscillator) has a fixed number of times it is divided and the other oscillator’s dividing circuit can be changed in the number of times it is divided the VCO will have to change frequency to make the two frequencies going into the PLL equal (6 MHz/60,000 = 100 Hz, 10MHz/100,000=100Hz, 10.001MHz/100,010=100Hz). Most modern frequency synthesizers use the PLL process just described.

THE TUNNEL DIODE

2007-04-13T14:07:00.000-07:00

A standard NP junction diode will maintain a forward voltage drop of .2 volts for a germanium diode and .6 volts for a silicone diode. If you have a voltage source that is connected in series through a potentiometer a fixed resistor and a standard diode when you measured the voltage across the forwarded biased diode you would see the constant .2 or .6 volt drop as you change the potentiometer’s resistance up and down. As the potentiometer’s resistance decreased the voltage across the fixed resistor will raise because there will be an increase in current.

Now if you take the same circuit described above but replace the diode with a tunnel diode you will get a very different action. When you first start to decrease the resistance of the potentiometer the current will start to rise and thus the voltage across the fixed resistor will rise. As you continue to decrease the resistance, at a certain point, the voltage across the fixed resistor will start to drop because the current is dropping. So now with the same applied voltage but with a decrease in resistance the current decreases instead of increasing. This is what is meant by negative resistance.

Using this phenomenon a Dynatron oscillator can be constructed. If an LC tank circuit could be constructed that had no resistance then when voltage was applied and removed it would start oscillating and would continue to oscillate as the energy transferred back and forth between the capacitor and the inductor. We know that such a circuit does not exist that is why there needs to be some type of compensation for the energy that is lost. In the case of the dynatron oscillator that energy is replaced by the negative resistance possessed by the tunnel diode placed in parallel with the LC circuit. When the negative resistance and the positive resistance become equal they will cancel each other out and the circuit will continue to oscillate.

Not only can the negative resistance be used as an oscillator but it can also be used as a very low noise amplifier and thus make excellent preamplifiers for VHF, UHF, and microwave receivers.

The tunnel diode was very popular in the early to mid 1960s but the newness wore off and so did the interest but they can still make some interesting and useful projects for the ham shack. They also provide some very simple projects.

THE LOWLY DIODE

2007-04-06T19:21:00.000-07:00

When introducing the diode as a subject most people with a little electronic knowledge will just say, “ho hum what can be said interesting about the diode?”

Actually books could be written about the diode, large books. A simple definition the diode is an electronic device which allows electrons to flow in one direction with much less resistance then in the other. It could be called an electron check valve. A check valve is a valve which allows fluid to flow in one direction but will not allow it to flow back. The valves in our heart are check valves.

When speaking of the diode we usually think it started with Thomas Edison’s discovery in 1880 which he patented in 1883 but the real discovery of the diode goes back further. Edison only rediscovered thermionic diodes. The thermionic diode effect was found by Frederick Guthrie in 1873 but Guthrie was not credited with the fine because Edison patented it.

Then the normal thinking is that the semiconductor diode came many years later but the year after Guthrie found the thermionic diode Karl Ferdinand Braun discovered the crystal diode effect which was used by early crystal radios. That little “cat’s whisker” crystal detector used in those early radios was a solid state diode. The “crystal” was usually made of galena, a naturally occurring sulfide ore of lead, thus it was a natural semiconductor. A small metal wire called a “cats whicker” was moved around the surface of the crystal, which was mounted in a metal container, until a sensitive point was found. That sensitive point was nothing more then a naturally occurring PN junction. If you hold up a clear glass solid-state diode today you can see that a cat’s whisker is still used in the diode.

The diode has many uses in electronics. They are used as rectifiers, modulators and demodulators, amplifiers, oscillators, capacitors and regulators to name a few. A magnetron, the heart of a microwave oven, is a diode.

Come back next week as we will look at the tunnel diode, a truly fascinating device.

A HELPFUL TOOL

2007-03-30T18:17:00.000-07:00

During my years as a radio technician I have seen many problems that were simple but difficult to find. There were times when a mobile radio will not be operating properly but when it is tested it is well in specs. Putting a directional wattmeter on it might show the reflected power to be well in acceptable levels but the unit still does not function well. Here is a tool I found to be very helpful in cases like that.

The tool is very simple. Use an antenna with a metal Motorola antenna mount and a male compression N connector for RG8U. Cut the antenna so it will reach through the N connector where the center pin would normally go and move the coax side of the connector down flush on the metal nut for the antenna mount. Use a hack saw or flush cutting pliers (if you use pliers be careful not to nick or break them these antennas are very hard to cut) and nick the antenna where it will be flush with the end of the connector. Remove the connector and cut the antenna at the mark. Shape the end of the antenna with a file. I said shape not sharpen because you don’t want it to come to a sharp point but you do want it to easily insert in the mating connector. Place the connector body back over the stub left from the antenna until it is snug against the metal nut and solder the two together. This is a little tricky and takes a lot of heat but as you can see from the photo it can be done. Throw away the center pin, the inter parts used to hole the coax, and the compressing nut.

Now use a double female barrel or a coax jumper with a female N connector on one end and connect it through a directional watt meter to a dummy load. Now see if there is any power reaching the watt-meter and if there is compare the output of the transmitter to the power on the watt-meter. If you are having problems matching the antenna then place the watt-meter on the transmitter side of the feed line and run the jumper from the antenna mount to a dummy load.

If the coax is good and the connector is properly installed on the coax then the reflected power should be near zero and the power on the transmitter side and the power on the antenna side should be close to the same. If this is true then you know the antenna is either not touching or making good contact with the mount or it is cut to the wrong length.

Some times the problem is caused by old coax having a very high loss. Other times coax will be cut, usually where it has been routed over a sharp edge and the vibration has cut it through. Sometimes it is a screw that has been run through the coax. I have had a few where everything looked good, dc wise they checked good, the connector was on good but the unit did not work and it was with this tool I was able to positively identify the problem.

I would say about 95% of the mobile installation failures will turn out to be a bad connector. So I usually just change the connector first getting to involved in trouble shooting but when that does not cure the problem then I use my tool to try to understand what is going on.

You may wonder about the earlier statement, “…it might show the reflected power to be well in acceptable levels.” You might think that is not possible but it is very possible, I have seen it several times. The coax can act as an antenna depending on where and how the coax is damaged. If this is the case the reflected power will change as the length of the coax jumper between the radio and the watt-meter is changed. These do not work well as an antenna. The other thing that can happen is the coax is old and has a very high loss thus it acts as a dummy load.

This is not a tool every ham should have because it is very rare you will need it. It would be a good project for a club to build and then make it available to members. It would be good then for all the members with mobiles to use it to test their installation making sure their ham shack on wheels is operating at its peak performance. When working through a repeater it is surprising how bad transmission and reception can be and not be noticed.

THE REGENERATIVE DETECTOR

2007-03-23T18:58:00.000-07:00

From 1896 when Guglielmo Marconi invented the wireless telegraph until 1901 when he added a tuned circuit to the receiver the radio receiver was just an antenna connected to a wire which went to a detector. After Marconi added a tuned circuit the receiver had a little selectivity. It was not until 1906 when Lee de Forest added the grid to the diode and the receiver was able to have something more then just passive devices. With the grid RF amplifiers could be added before the detector and audio amplifiers after the detector which was a great improvement.

The tuned radio frequency (TRF) radio became the receiver of choice. The problem was that each stage had to be tuned separately and the tubes had to have low amplification or they would oscillate. The TRF remained the only way to add amplifiers ahead of the detector until Edwin Armstrong conceived the idea of superhetrodyne during WW1.

In 1914 Edwin Armstrong, an amateur radio operator, patented the regenerative detector. This was a real break through in radio receiver progress.

The regenerative receiver uses a positive feedback which greatly improves both the sensitivity and the selectivity. In the earlier days the receiver had, compared to today’s receivers, a very large coil for the input tuned circuit which fed the grid. It had a. coil of just a few loops of the wire in the place circuit. The coil in the plate circuit, called a tickler coil, would be physically moved in the proximity of the input tuned circuit until the positive feedback was almost enough to cause oscillation when receiving an AM station and it was adjusted just into oscillation to receive a code station. The oscillation would produce a heterodyne, two signals mixed in a nonlinear circuit which result in an output of the sum and the difference of the two input frequencies, which could be heard as a tone this allowed true CW to be used. Up to then only MCW could be used.

The gain of a regenerative receiver using just one tube can be up to about 20,000 and if a MOSFET, not developed until many years later, is used a gain of 100,000 is possible.

Then in 1922 Mr. Armstrong patented the Super-Regenerative receiver. The super-regenerative detector uses a “quenching” frequency usually about 20 KHz to 30 KHz though other frequencies are also used. Using the quenching frequency to quench or stop the detector’s oscillation there is no need to adjust the tickler coil. This makes the receiver easier to operate and increases the sensitivity. Because they are inexpensive and easy to make these receivers are still being built and used, mostly in VHF and UHF ranges, today.

One of the biggest disadvantage of the regenerative and the super-regenerative receivers is they radiate a lot of noise over a wide area of the frequency on which they are being used. Back in the Sixties Heath Kit had a little 10, 6, and 2 meter transmitter receiver kit called the Tenner, Sixer, and Twoer. These units used a super-regenerative receiver. In 1965 I had a twoer installed as a mobile. That was the year the United States Coast Guard transferred me from Brownsville, TX to Coast Guard Radio Station New Orleans (NMG). My wife and I were driving around Metery (just across the river from New Orleans) looking for a place to live. We had our infant daughter with us. The Metery Police at that time were using 150 MHz radios. As we were driving I saw a police car sitting on the side of the road. I was very careful to obey all laws as I passed him. I came to a full stop at the stop sign. And when I pulled out from the stop sign he followed me and shortly on came the blue lights (I had never seen blue lights before but I guessed they meant the same as the red ones) so I pulled over. He stopped right behind me and one officer got out of one side of the car and the other from the other. They approached the car with hands on their guns, though they were still holstered, and one grabbed my door with his free hand and the other grabbed my wife’s door. The questions started flying, who was I, why was I there, and finally what is that radio. It took years before I understood why they pulled me over. My tower opened up their squelch when I passed by and again when they came up behind me and they wanted to know why.

Just as a little added note. Erwin Armstrong invented the FM transmitter and receiver a few years after the super-regenerative receiver.

Mobile Installation Power Ground

2007-03-17T18:02:00.000-07:00

On the Technician class test there is a question which says, “What is the purpose of a fuse in an electrical circuit?” and the answer is, “To interrupt power in case of overload.” In the Gordon West Technician Class Q And A book it says, in the added notes, “Place the fuse as close to the battery as possible.” (Page 162). That is good advice because if for any reason the positive wire’s insulation is damaged and the wire touches the chassis or engine (a hot manifold is a frequent cause of this problem) then it will blow the fuse if it is close to the battery but not if it is between the radio and the short.

On that same page it shows a schematic of an installation and it shows a fuse in the negative line. Many hams think that is unnecessary because you will not cause a short if the negative wire touches the metal of the vehicle. So why place a fuse in this line?

The diagram shows the negative wire going straight back to the negative terminal of the battery. What I am about to say I have personally seen this happen more then once so it is not hypothetical. If the battery cable develops resistance between the cable and the body of the vehicle by rust or corrosion or the wire itself corrodes to the point that it is not a good conductor this type of installation can cause problems.

When the engine is being started a lot of current is being drawn from the battery. The current seeks the path of least resistance and if that path happens to be between the radio, through the negative wire, to the battery then that is the where the current will flow. The current will only be a percentage of the overall current flow but it doesn’t take much of a percentage to overload the wire and smoke will result. Frequently what will happen in this configuration is the unit is not grounded well at the mounting bracket but the shield side of the coax makes a good ground by the antenna mount. The current for the starter will flow through the coax shield to the coax connector on the radio then on to the negative wire to the battery. If that wire is not fused the coax shield will smoke. If the radio is grounded at the mount the negative wire to the battery is not big enough to handle the load and it will smoke. Either way there is a fire danger.

Personally I do not recommend this type of hookup. If you do this and the fuse blows you may not know it is blown because the radio will find sufficient contact between the mounting bracket and/or the antenna ground to continue to operate. The resistance does not have to be high enough that the vehicle will not start to cause this phenomenon. Now the antenna ground and the mounting bracket are not designed to be the ground sores for the DC power of the radio and it will cause more problems then you can imagine. Believe me as a two way radio technician for many years I have seen these problems and they can drive you crazy. I suggest that you run the ground wire to the chassis of the vehicle. Use an eye connector with one outer locking lock washer between the head of the screw and the lug and another between the lug and the chassis. Scrape the paint off the place where the lug will come in contact with the metal. Run the screw down tight but do not strip it out.

I can not tell you how many problems I have found that were caused by a poor ground connection.

THE LITTLE GLOWING MARVEL

2007-03-09T20:41:00.000-08:00

A statement was made on the history channel that the vacuum tube had to be invented before the radio could be invented. The logic behind the statement was that oscillators could not be made before amplifiers. It is true that oscillators could not be built before amplifiers but radio communications predates the use of these little glowing marvels as amplifiers by 20 years. A spark gap and a coherer detector started it all off. Later the Peroxid of Lead detector came into being followed many others including the Electrolytic Detector, the Barretter, Carborundum Detector, the Silicon Detector, the Perikon Detector, and the Galena Detector, the last three could be lumped together and called a crystal detector. All of these preceded the use of the vacuum tube.

Though they precede the use of the tube they do not precede the vacuum tube. The summer of 1895 is considered the beginning of radio communications when Guglielmo Marconi was able to transmit and receive a signal over approximately 1.5 kilometers (approx. 1 mile). The vacuum tube history began in 1883 when Thomas Edison, while trying to improve the incandescent light, discovered that if he placed a small metal plate in the glass envelope of the light and attached the metal plate to a positive charge while the negative charge was on the filament electric current would flow across the vacuum inside the envelope. This came to be known as the Edison Effect but Edison did nothing more with it.

In 1904 Sir John Fleming found he could use the Edison Effect to detect radio signals. So over the 9 years between Marconi’s invention and Fleming’s discovery the vacuum had no connection to radio. It was not until 1915 when Lee DeForest placed a grid inside the diode between the filament and the plate that amplification was possible. With the invention of the Audion, the first name for the vacuum tube, true CW became possible. The Audion later became known as the Fleming Valve which it is still called in many countries but in the United States of America it is called a vacuum tube.

Not only did it provide the necessary essential to make oscillators and detectors but amplifiers and mixers which allowed the superhetrodyne radio.

It was these little glowing marvels that bridged the road between the wide band, short range, loud smelly spark, and insensitive passive detectors and the present solid state DX in a box radios.

WHY ARE WE CALLED HAMS?

2007-03-03T15:27:00.000-08:00

This week I was asked a question, that I have been asked many times before, “Why are hams called hams?” The absolute unquestionable answer to this question is unknown but the following is believed by most word authorities to be accurate.

In those early days of radio communications, as is true today, some radio operators were experimenters, traffic handlers, and rag chewers who did this as a hobby or just for the pure love of radio. Then there were those who make money by radio communications. Ship board radio operators and land based radio operators were professionals and the previous group were called amateurs. When amateur radio operators started to be called hams all the other uses of radio, such as business band radio, police radio, broadcast radio, etc., had not come into being. There were just amateur and professional radio operators.

It is believed that the term ham when speaking of amateur radio operators and the term ham used to speak of an actor is of the same origin. When an actor is call a ham it means he or she is not acting professionally but is acting like an amateur. So the actor was an “am”, which was short for amateur. The British frequently place an “H” sound in front of words starting with a vowels, or at least to the American ear it sounds that way. So “am” became “ham”.

So the name ham is just a short form of Amateur. It is an insulting name for an actor but we carry the name with pride.

Please to those of you who are British this is not a criticism of the way you speak in any way, how could I criticize I mean after all the language is not called American. I am really glad the “H” was placed in front of the word. It is hard for me to think of myself as an “am”.

______________________________________________________________________________________________________________________

Added Note:

I have learned that money can be made from people who want to advertise their products and services on blogs. This opens up a way we hams can enjoy each other’s blogs and make a little cash at the same time. I am looking for a group of hams who would like to form a network using blogs about ham. It will be fun and we can make a little extra cash to buy a new ham rig. If you are interested please contact me via the contact key below or email me at hamslife@veriuni.com or go to http://hamslife2.blogspot.com where you can learn more.

Bill

WA6OHP

RAMSEY HF RECEIVER KIT REVIEW

2007-02-23T16:28:00.000-08:00

If you search on eBay for Ham Radio Receiver Kit you will most likely find a 40, 30, or 20 meter receiver kit by Ramsey Electronics. You might also see an 80 version of these receivers but it does not seem to be as popular. In fact you will probable find more then one of all three up for bid at any one time. A search at 0909 on 02/23/2007 revealed there were 4 Ramsey receivers up for bid. There is one each of the afore mentioned receivers and a 2 meter FM receiver. All have 1 day 6 hours 5 minutes left and no bids.

For the purpose of this post only the HF single band receivers will be considered. The 10, 6, 2, 1.36and .68 meter receivers are super heterodyne and FM receivers.

Using the same information in the advanced search, under Completed listings only, eBay showed 9 with two 20 meter receivers having sold and one sold for $36.00 and the other went for $34.99.

Why do these little units not sell? They come with all the hardware and case. They have an instruction manual that is very complete with a check off list for each part as you install it. They are simple enough to build. So the real question is how do they perform?

You can not expect a receiver that retail for under $40.00 USD to be a top of the line receiver but to barely be able to hear a signal of 50 μv is unacceptable. Maybe this is why they are not selling.

5 μv is nothing to shout about but it is on par with other autodyne receivers. That is about what you will get with one simple modification.

If you or someone you know has one of these radios and has found L1 does not peak when aliening the receiver that is because there is an error in the design of the PC board. The manual for the HR30 can bee seen at http://www.ramseyelectronics.com/downloads/manuals/HR30.pdf . Scroll down to page 10 and you will see a diagram of the PC board. Looking at the front of the coil, that part closest to R1 and R2, on the corner closest to L2 there is a solder pad to attach one leg of the coil.

L1 is called a coil but it is actually a transformer. The input comes from R1, RF gain control, and the output goes to the input onU1, the RF amplifier, detector and BFO. The solder pad which was pointed out above is the other side of the input coil of L1. The reason this is left open is to make a lose couple on the front end of the receiver and the antenna. The problem is the receiver is not sensitive enough to work well with a loosely coupled input. Running a jumper wire from the solder pad to ground will raise the sensitivity of this unit about 20 dbs. I have not yet had a chance to test this modification on the 80 and 40 meter version of this unit but they use the same PC board and the same coils so I am sure the results would be the same.

These radios run on a 9 volt battery. Owners may be tempted to place a connecter on the back and connect them to a 12 volt power supply. The unit should be able to withstand the voltage but it would be recommended they ad a 10 volt regulator inside the unit to protect it. There is plenty of room. They will probable have to add some choke coils at t he input because autodyne receivers have a bad tendency to pick up AC and it can prove to be very difficult to keep out.

While I would not call these great units over all I would say these receivers are not a bad unit for the price. For the new kit builder they do give a very easy unit to construct and take pride in.

If you or someone you know has had experience with these units or any other Ramsey Electronics kits please send me an email at hamslife@veriuni.com and let me know your experience and opinion.

WHY IS IT CALLED CW?

2007-02-16T14:22:00.000-08:00

For years after becoming a ham I asked why CW was called CW. The answer was always the same, “CW means continuous wave” but it is not continuous because by nature Morse Code is made up of broken carrier or wave. When I continued with this line of thought again I would get a single answer, “I don’t know why.” Oh if I had just talked to a ham who had been one for long enough to have used a Spark Gap transmitter I would have received my answer.

The first wireless transmitters were basically nothing more then a voltage source, a coil, an arc or spark gap, a key, an antenna, and a ground. The coil was frequently a spark coil from a model T Ford. The transmitted signal was over the whole RF spectrum. Later tuned circuits were added which suppressed the RF signals generated above and below a given wave length but the output was still a very wide portion of the band.

Another problem with the Spark Gap transmitter was the signal would dampen out. The signal could not be sustained for a long period and thus the spark must be continuously interrupted and restarted. This meant a lot of noise but that was good because the receivers were only passive devices. They had no amplification just a detector and those early detectors were not all that efficient. Certainly they did not have a bfo but with all that noise none was needed.

After Lee de Forest added a grid to the Fleming valve, now called vacuum tube diode, in 1906 he found it could be used to amplify a signal. This allowed the construction of the regenerative receiver and soon the audion, the name de Forest gave his triode, was also used to as an oscillator to generate the transmitted signal. The first ham stations using this new form of generating and detecting an RF signal usually consisted of a single audion being used as both the transmitter and the regenerative receiver.

The definition for Continuous Wave is a single frequency sustained at a constant level. If a carrier is modulated it will contain sidebands and in the case of FM not only sidebands but also the frequency of the carrier itself changes. Thus to qualify as CW it must be unmodulated. CW was also know as "undamped waves", to distinguish damped wave generated by the Spark Gap transmission.

There were a few hams that experimented with trying to modulate spark gap transmitters but for the most part all wireless communications were by Mores Code.

Now the continuous wave could be sent but it contained no intelligence. To use it for communications it had to be interrupted into dots and dashes thus the true name for this communications was actually Interrupted Continuous Wave or ICW but the I was dropped and it became just CW, the necessity for the keying was understood.

There was a period of time where there were both CW and Spark Gap signals on the air. Those using Spark Gap usually had passive detectors and thus were unable to read the CW signals so amplitude modulation was added making it Modulated Interrupted Continuous Wave or IMCW which was shortened to MCW.

Now if someone ask you why radio Morse Code is called CW you can tell them it is short for ICW.

Added Note:

I have learned that money can be made from people who want to advertise their products and services on blogs. This opens up a way we hams can enjoy each other’s blogs and make a little cash at the same time. I am looking for a group of hams who want to form a network using our ham blogs that will be fun and profitable. If you are interested please contact me via the contact key below or email me at hamslife@veriuni.com .

Bill

WA6OHP

HOW TO GIVE AND RESPOND TO A DISTRESS CALL

2007-02-09T12:11:00.000-08:00

First reaction to a distress call should be, “this is real can I help.” Then listen to the whole message to see if you might have an ability to render assistance. If you are not in a position to help you should still remain on frequency and listen. If there is no response by a station who can offer assistance after a few seconds respond by acknowledging you heard the call.

The way to acknowledge a Mayday is simply his call sign, “this is”, your call sign “roger your mayday out.” If you are in a position to assist then your response would be, after call signs, “roger your mayday” then quickly tell how you can assist. If you are going to their assistance give your position and estimated time of arrival (ETA).

The reasons for acknowledging the distress call when no one else who can render assistance responds are: 1. the distress station will know they have been heard and that the signal is getting out. 2. The skip maybe jumping over the top of someone who could help and by responding your signal may be received by that station and you could act as a relay. 3. You can call the authorities who can help or if you do not have a telephone available you can call for someone else on the air who can assist. Remember there may be people who can hear you and can not hear the distress station.

If it is an SOS the response is basically the same. The receipt response is “r SOS AR.”

Stay on frequency and listen as long as you can or until the distress is over. By over I mean help is on scene and danger is over.

When taking information or when giving information there is an order of importance. Who is in distress is contained in the call sign. The exact location of the distress is the most important. No one can help if they to not know where it is. Next in order of importance is the nature of the distress (if it is a boat taking on water the nature of the distress would include type and size of the vessel).

With just that much information help can be dispatched but the next order of business is how many people are involved in the distress and are there any injuries. Then finally how much longer can the aircraft remain in flight, the ship or boat remain afloat, or what ever condition that caused the distress will remain sufficiently stable to support those in the distress.

This information is all important. If you are receiving a distress signal and you are going to relay this information to the authorities try to get all of this information before calling. If you are sending a distress call include all the above information in your distress call because your signal may be heard by someone who is not able to respond back but who can help.

When you receive a distress call it should be passed on through proper channels. If the distress is a ship at sea, no matter what flag it is under or where it is, if you are in the United States of America that channel will be the US Coast Guard. If it is an inland boat the USCG can still assist. If it is an aircraft of any kind then it will be the FAA who needs to know. If it is an automobile or other land based distress then your local state police will be able to pass the information to the proper authorities even if the distress is not in your state.

But in the USA most of the country has 911 for emergency. Using this will not require you to look up any number. When you call 911 make sure you identify that you are a ham radio operator passing on the information by saying, “I am an amateur radio operator and I just received a distress call.” Then let them ask the questions. If you do this things will go a lot smoother.

Do not let the 911 operator argue with you because it was received on ham radio. Every distress signal is considered real unless proven otherwise.

If you hear a distress call which does not include a call sign it is legal for you to respond. Non hams can use amateur frequencies to make a genuine distress call.

Keep a log of all the activity which will include time, date, frequency, mode, list of all participants, and what was said. Sign and date the log and keep it. This can be used as an official record if needed and if it is not needed you will probably want to have it just so you can go back to remember it. You should keep that log for at least 5 years.

Armed with the information in these last three posts you should be able to handle any distress. The biggest thing is don’t panic. Stay calm, (OH SURE), well try anyway and do the best you can.

Let other hams know about these blogs because every ham radio operator should be ready to respond to a distress. It is our responsibility to be ready.

73 for this week

Bill WA6OHP

DISTRESS AND HAM RADIO OPERATORS

2007-02-02T14:07:00.000-08:00

A ham radio club in New Jersey held a meeting one evening where they had a special speaker talking about distress communications. As I sat listening to the repeater and working one of the hams that had been at that meeting started calling “Mayday” just trying to be funny. Either the speaker missed a very important part of his subject or someone was not listening when he did. Others came on and they were all joking around about the whole thing when I broke in and told them the little story that was in last weeks article here on Ham’s Life.

Distress calls are serious business. In the United States of America a false distress call can result in 6 years in a federal prison (the time has been decreased sense 1965) plus $250,000 in fines. On top of that some states, if they render state assistance, can charge the person making such a call for the cost to the state for responding and that can add up to several thousands of dollars.

That is enough threats now for some information about distress.

After Marconi revealed his invention to the world the shipping industry was quick to employ it on board their ships. Ships could communicate with land stations giving and receiving various bits of necessary information to improve the efficiency in transporting their load. The radio operators came from the most likely source, the land telegraph operators.

The railroad telegraphers and the message wiring companies had adopted a special code which was used to notify that this message was for everyone listing. It was CQ so when they went aboard ships they carried the same code. When in distress most operators would add a D to the end of CQ making it CQD. But there was no standard so others used DDD. There was some confusion so at the second Berlin Radiotelegraphic Conference 1906 the subject was discussed at length. The conference finally accepted that SOS would be the acceptable international distress calling signal.

Some think SOS was chosen to mean Save Our Soles, and others argue that it means Save Our Ship but the truth is it doesn’t mean either. The Marconi Yearbook of Wireless Telegraphy and Telephony, 1918 made it very clear with these words, "This signal [SOS] was adopted simply on account of its easy radiation and its unmistakable character. There is no special signification in the letter themselves, and it is entirely incorrect to put full stops between them (the three letters)." SOS is a single character not three separate letters (not … / --- /… but …---…).

Voice communications became possible and this required a voice equivalent to the SOS signal. The French expression “M'aidez" (which means “come help me” though apparently not grammatically correct) was considered. The word took on a more English sound and thus became Mayday (one word).

If you are discussing a holiday which comes on the first of May you do not call it “May Day”. Someone who does not speak English may have no idea what you are saying but hear and recognize that word “Mayday”. Just don’t use those two words together on the radio unless there is a real distress.

Distress means eminent danger to life. My car won’t start and I need a tow is not a distress. My car is hanging over a cliff and may plunge over the edge at any time and I can’t get out is a distress.

Next week the subject of distress will continue with how to give a distress call and how to respond to a distress call that is heard. Be sure to come back and invite a friend to visit this blog.

DISTRESS CALLS ARE NOT A JOKE

2007-01-26T10:13:00.000-08:00

Have you ever watched a TV show where the police officer asks the suspect “where were you” on a certain day at a certain time and you find yourself trying to remember where you were at that time? Sometimes I find myself thinking, “could I answer that if I were asked” and frequently I have to say “no” but if I was asked where I was on 04/01/1966 at two PM Central Standard time I could answer. I was on watch at NMG also called Coast Guard Radio New Orleans.

A distress signal had been received reporting a supper tanker was on fire in the Gulf of Mexico. The distress had been sent on a ham frequency. The operator sending the message said he was the ship’s radioman and that, because of the fire, he was unable to reach the ship’s radio room so he was using his ham radio in his room.

Another Radioman who was off came over and told me he was sent to relieve me so I could go over to the ham station and find out what was going on.

There were a few things that were not adding up to me but when you are in the middle of a distress you work the distress traffic and try to figure out the abnormalities later.

The operator said he was trapped by the fire. The Coast Guard had launched ships and planes to assist. Lives were at stake.

A distress rebroadcast was given on 500 KHz (CW distress and calling & answering frequency) and on 2182 KHz (the voice equivalent to 500 KHz) so vessels in the area, who most likely would not have heard the original call, could go to render assistance. It is very expensive for a large ship to change course but when lives are at stake that is what they will do. Military, Personal Pleasure, and Commercial craft from all nations will divert to assist. Airplanes will change course to give visual assistance. This sort of thing becomes an International incident.

News flashes were sent out on radio and TV thus families of the distressed vessel became anxious.

There was a problem. The Radio Direction Finders (RDF) and the position given in the distress message were not in agreement. I was given this information but no one told me where the RDF’s were pointing. When I questioned the operator about this he told me he was not sure of the exact position and that was only an approximate position.

After about an hour the radioman on the distressed ship told me he thought he could escape by swimming under the fire. I told him to lock his key. With the key locked the continuous signal would allow the search and rescue team to lock in on him and more quickly respond.

Locking your key down and just sending a continuous signal is normally against FCC regulations but during a distress, and I mean a real distress, the regulation book is largely set aside.

The signal did not last for more then about two minuets and then went off. Others who were standing by came on for discussion. We were all wondering why the signal didn’t last longer.

We were all hopping that the signal was on long enough to get a good bearing and, as I found out later, it was.

The search party was very close but not in the Gulf of Mexico as he reported but in the city of New Orleans. The FCC was within blocks and the locked key allowed them to go right to the house. The reason the signal went dead was the FCC shut it off.

It was a 17 year old ham who wanted to play an April Fool’s joke. It was a joke that cost several hundred thousands of dollars and in the end nobody found funny.

As a little side note, the ship that was reported to be in distress was a real vessel and they received the distress rebroadcast and sent a message to NMG stating that they were not on fire or sinking. The conversation must have been interesting when the ship’s radioman delivered the distress rebroadcast message to the ship’s captain.

I did not hear what finally happened to the kid but I did have a chance to talk to the Field Engineer at the New Orleans FCC office and I asked him about it. He told me that the court had found him guilty but had not yet sentenced him at that time. The FCC was asking for maximum penitently which could be up to 10 years in a federal prison, a very heavy fine, and a loss of all amateur radio privileges for life.

The moral of the story is a false distress signal is not a joke. It is not a game. Never ever give a distress call or report a distress call that is false.

Next week I will discuss the proper procedure for a real distress.

AMPLIFIER’S FLYWHEEL

2007-01-19T19:30:00.000-08:00

As said in the last article the class C amplifying device (tube/transistor) only conducts during a small portion of the cycle yet the output is a sign wave. This accomplished by so called “flywheel effect” of a tuned circuit.

Most people understand that the flywheel is a heavy wheel that uses its centrifugal force to swing a piston driven engine around so it can return to the power stroke. The tuned circuit responds in a similar manner electronically.

A coil will store power in its magnetic lines of force. When the power is removed these lines of force will collapse back into the coil thus generating a voltage in the opposite direction as that which was applied. A capacitor also stores energy and when the circuit is completed between the terminals it will produce a current opposite to that which flowed during its charging. If a DC voltage is placed on a coil with zero resistance, no such coil exists, the instantaneous voltage will be equal to the source and the current flow will be zero. As the magnetic lines build the voltage will drop and the current will increase until the voltage is zero and the current is maximum level. As the capacitor charges the voltage will go up until it reaches the value of the source and the current will drop to zero.

When AC is applied to the capacitor it will start to charge during as the current starts to flow in one direction in one direction and then will start to discharge after the voltage peak starts back down towards zero. It will do the same on the other side of the AC wave form. This action will cause the current to be limited in a fashion similar to resistance except resistance results in power loss due to its generation of heat but this action of the capacitor, called capacitive reactance, does not produce heat. The larger the capacitance of a capacitor the smaller the reactance will be.

Considering the reaction of the coil, also known as an inductor, it should be easy to see that there would be an opposite reaction to the AC and this is known as inductive reactance.

Reactance, like resistance, is measured in ohms. When the inductive reactance and the capacitive reactance are equal the coil will discharge into the capacitor and when the clasping inductive field and the charging capacitor voltage are equal the current will cease to flow and the capacitor will discharge back through the coil. If there was no resistance and if no energy was radiated this action would continue on indefinitely but there is resistance and energy is radiated so the process dies out. If the output from the amplifying device continues to supply energy then the action can be sustained. This action is called the flywheel effect and it is how a class C amplifier can put out a sign wave.

If the tuned circuit are resonate at a multiple (harmonic) of the frequency being injected into the amplifier the flywheel effect will continue between the pulses then will be reenergizes on the next pulse. For example if the input circuit is tuned to 2 MHz the output circuit is tuned to 4 MHz spikes from the amplifying device’s output will be every other cycle and the amplifier’s output will be 4 MHz.

If the output is fed back to the input when power is placed on the circuit the tuned circuit will start vibrating and if it is in phase then the output will support the input and the output will continue to keep the tuned circuit vibrating. This results in the results being an oscillator.

My wife says when people ask me what time it is I have the bad habit explaining how to build a watch. That is a little of what happened here. My original intent was to explain what a linear amplifier is but I guess I got carried away. I hope you enjoyed this explanation of how amplifiers work. If you have questions or comments please email me at hamslife@veriuni.com and be sure to put the words Ham’s Life in the subject line so I don’t think it is spam. I need feedback so I know what people would like to see.

Starting next Friday this blog will start a short series on distress communications.

BILL WA6OHP

AMPLIFIER CLASSES

2007-01-12T10:50:00.000-08:00

Mysore HAM - VU2MUD: Fascinating World of HAM Radio - Part 2

2007-01-07T16:56:00.000-08:00

Mysore HAM - VU2MUD: Fascinating World of HAM Radio - Part 2

WHAT IS A LINEAR AMPLIFIER?

2007-01-05T20:54:00.000-08:00

FCC Dropping CW Requirement! WHAT DO WE DO NOW?

2006-12-22T15:03:00.000-08:00

On December 15, 2006 the Federal Communications Commissions made a historic decision in regards to the testing requirement for a ham license in the United States. The FCC announced that it was going to drop all Morse code proficiency testing for Amateur license.
This has spawned a lot of conversations in the ham community. There are a lot of differing opinions. Some are in favor of the action because now they can upgrade without having to take a code test or because they do not believe CW is necessary element to be an amateur radio operator. Others are opposed to the action based mainly on two reasons. One reason is the belief that the quality of operators will deteriorate. The other argument is that CW is more efficient in emergency communications.
The FCC rejects the objection stating, "The Commission previously addressed the essence of this argument and concluded that most emergency communication today is performed using voice, data, or video techniques," they also rejected the assumption that the Morse code requirement helps keep bad apples off the ham bands.
To argue the issue is at this point is fruitless because the FCC has spoken and they are not going to change directions now, but discussing the issue and venting our feelings is a positive thing.
The effective date is still unknown but it will take effect 30 days after the document appears in the Federal Register. This is expected to occur in January so the rule will most likely take effect is February.
So if the FCC is not going to change we have to adjust and determine what we are going to do now.
The ham society has effectively policed the ham bands in the past to keep bad apples off the air and I see no reason why this should change. I am not sure just how many poor operators have been kept off the bands by the CW requirement but sense the Technician license has dropped the code requirement I have not personally noticed an increase in undesirables showing up on the VHF bands.
What about the use of CW for emergency operations? CW is still a viable means of communication especially when passing traffic. It is simple and easy to set up. The equipment can be made very portable. The power requirements are relatively small. Messages can be delivered, by really good CW operators, faster and with greater accuracy then by voice. Many may find that last statement hard to believe but notice I said, “really good CW operators” and by that I mean one who can send and receive at accurately 30 WPM or more. When sending CW words do not have to be spelled out phonetically and they will still be just like it is in the original. The sending operator knows how fast the receiving operator can receive and sends at that speed if he or she is able where as a voice operator usually slows down to be sure the message is being copied correctly.
Knowing code provides the possibility of providing communications in unusual circumstances. In an emergency situation a flashlight can be used to send information or the horn on a car. If a person who knows code is unable to speak but is able to move even so much as to blink their eyes that person can send a message. But those situations will not result in communications unless there is someone who can read Morse code. There have been rescues because a ham knew the code.
Though the FCC has dropped the testing requirement it has not eliminated CW operations. Those who believe in CW need to pull together and help others to see the importance and fun of this mode of communications. Be willing to teach classes or individuals. Get out and show the value of CW in emergency operations by having mock drills on CW and being available when it is needed.
Now we can sit back and let the other person do it and if we all do that, well I don’t need to finish that one.
Use the comments section and let me know what you think.
Be sure to look at the ads that appear with these messages. They pay for the publishing.
73
BILL
WA6OHP

Over 46 years in ham radio

2006-12-08T16:21:00.000-08:00

September 1960, as a senior in High School, I received my first Ham Radio license. It was a Novice license. We had a small portion on the 80, 40, and 15 meter CW bands and we were allowed to use AM on the 2 meter band. The maximum input power we were allowed was 75 watts (with CW that is enough to do a lot of DXing.). The license was good for 1 year, not renewable and anyone who had ever held a novice license was not able to get another. There was real incentive to upgrade in that year. My upgrade was to a Conditional class which was the same as a General class but you had to meet certain qualifications, mine was the distance I lived from the FCC office where the tests were given, and it was given by mail. The test had to be officiated by the holder of a General class or higher. W6CC officiated my novice license. W6CC started his ham activities before licenses were issued thus his first station used a spark gap transmitter. W6CGJ, a retired farmer, officiated my conditional class. My CW teacher was K6KRL a retired railroad telegrapher who started his career in the 1880s. Another big influence was K6BJV the county tax assessor who gave me the push and pointed me in the direction to get my license. I have sense gone on to get my Extra Class license. We all owe much to others and should try to give back. My goal is to give some interesting or informative tidbits which I hope you enjoy. The information will not change each day at first but check back and as the readership grows it will change more often. The ads you see support this so please click on them and look at what they have to offer. That is how this site is supported.

Be sure to save this in your favorites and come back. Let me know your interest dealing with ham radio so I can know what my readers want to read.