K5LAD - 50+ Years of Ham Radio Memories

Volume VII

Early Memories of Two Meters

 

Two meters always held an interest to me and this was quite a few years before I ever actually got a chance to operate on two.  Perhaps part of the reason it held such a fascination for me was, when I got my Novice license back in 1957, Novices could actually operate AM phone on a portion of the two meter band.   Whereas some new hams want to get their licensees to talk to people on CW, I really wanted to operate on phone and the need to learn CW was merely a path to that end.  I learned the code and raised my code speed but only to get to higher-class license.

When I was in high school I drooled over a two meter portable kit which was advertised in the electronics magazines of the day.  I think it was probably a super-regenerative circuit but there were few signals on that band so high selectivity was not as big a need.  Seems like the price was somewhere in the $35 range.  I read stories of Carl and Jerry in my Popular Electronics magazines and enviously wished I could talk back and forth to local friends like they were able to do.  I even thought about hiding a two meter AM portable in a briefcase and using it during study hall hour.  I don’t recall who I thought I would be talking to because I don’t think there were many (or any) locals operating on two meters during those days in the late 1950s.  In order to pursue those dreams, however, I must first obtain one of those radio kits and, alas, that was beyond my possibilities so that was always just a dream.

 

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When I visited the local ham dealer in Tulsa, I always spent some time twisting the knobs on the Harvey Wells TBS-50 transmitter they always had on display.  Not only did it have all of the Novice CW bands but also had a position for two meters and a modulator to boot.  I dreamed about operating two meter AM on this unit, although it was a transmitter only and I don’t recall extending the dream to some sort of receiver.  The price was always much above anything in my meager budget so I was destined to be only a knob twister.  As the years have now passed and I look back upon it, this was during the time when hams had to be more careful about TVI, and I have since learned that the Harvey Wells transmitter was notorious for its television interference problems.  I guess I should thank my lucky stars that I was unable to get that transmitter but I sure didn’t feel that way at the time.

Later, after college and newly married, I attempted to build a two meter converter from the ARRL Handbook.  Now, I had a job and a small income from my teacher’s salary (1964 – take home pay was $289 as I recall) I could buy some new store-bought parts to build my VHF converter.  I had read quite a bit about VHF building but until you actually get your hands into the process, there’s still much, much to learn.  I remember my converter looked pretty good but it was absolutely overwhelmed with random oscillations --- birdies.   I don’t recall ever hearing an actual two meter signal on my setup.  At the time, the Tulsa Repeater was in its infancy on 146.94 but I didn’t have an FM detector on my receiver and I was yet to learn about slope detecting a signal with the AM detector so if I accidentally ran across the repeater’s signal, I didn’t recognize it.  Actually, I don’t think I ever heard anything but birdies.   Still, my interest was strong there.

 By the following year, the Tulsa Repeater was really going great guns with most users running converted commercial FM radios.  There were a few General Electrics and a couple of others but most being used were made by Motorola:  5Vs, 41Vs, a few 80Ds, and even fewer 140Ds.  I sure wanted to get into that group but I didn’t have a radio and was yet to find enough bucks to buy one.

 Then a fortuitous event happened.  Our local ham club was closely affiliated with the Tulsa American Red Cross chapter and a local company gave the Red Cross a number of RCA Carfone VHF mobile radios.  The Red Cross worked out an agreement with several hams to get these radios out into service and also to provide more volunteers for the Red Cross.  If a local ham would buy two sets of crystals for an RCA Carfone, the Red Cross would give them the mobile radio to use while the ham promised to volunteer for RC service, generally in the Disaster Representative area.  The second set of crystals was used to provide a two meter FM radio for use in a Red Cross vehicle for the hams to use when out at a Red Cross activity.  Seems like, at the time, the cost for these two sets of crystals was less than $40 which was within my budget.  I was able to get in on this deal and was happy to have the opportunity.

 I worked with the Red Cross as a “Disaster Representative” for several years and had a nice 10 watt mobile during that time.   In recent years I’ve laughed at the name of my job with the Red Cross because it leaves you open for some really strange comments.

“Oh, you work with the Red Cross, do you?  What do you do?”

“I’m a Disaster Representative”

“A Disaster Representative, huh?  Just which disasters do you represent?”

 The year was 1965 and now that I had a two meter mobile, I wanted a base unit.  After all, I’m not in my vehicle (a 53 Ford) all of the time.  By this time we had moved to Turley, OK, a small community just north of Tulsa.  We lived in a rather depressed (and depressing) area but had rented a very nice two story house with lots of room and the rent was only $75 a month.  The owners had fled, er, moved from the area and were renting out their old house until they could sell it.  The lady of that family had operated a beauty shop which included the complete front area of the house which was completely glassed in.  It was very nice, had nicely drapes covering the windows, an air conditioner, and it made a super hamshack.

 I was beginning to successfully get on two meters, first with FM operation and later with AM.   I was a member of Army MARS and had received the shipment of a military surplus aircraft radio set, model number:  AN/ARC-3.  Quite a few hams had been using the surplus SCR-522 series on two meter AM and a few had even converted the ARC-1, which was a single unit transceiver which used the same crystal for receive and transmit.  The ARC-3 series was a much updated version of the SCR-522 and the ARC-3, with separate receiver and transmitter, was better for ham use.  All of these radios typically ran about 8-10 watts.

 

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[Here are the ARC-3 series – the transmitter (T-77) is on the left, the receiver (R-67) on the right]

 The ARC-3 receiver was also crystal controlled with crystals in the 8 MHz range and had a motor-driven shaft which tuned the variable capacitors to the frequencies between 100-156 MHz. with the proper crystal.  I modified my ARC-3 receiver by removing the military looking front and adding a nice aluminum front panel.  On that I built an 8 MHz variable oscillator with a calibrated dial – using mostly brand new parts too.   After removing the motor drive and soldered a shaft onto the variable drive shaft, I brought this shaft out the front panel and added a knob.   Since the variable oscillator dial would be on the same frequency for 100, 108, 116, 124, etc. MHz, when tuning thorough the whole range from 100 to 156 MHz it required using both hands.   The knob on the previously motor driven shaft would tune the multiplier stages and peak up the front end.  I kept the small window which was linked to the shaft and showed what area (between 100 and 156 MHz.) it was tuned.  The receiver was made for WWII aircraft to communicate on AM phone, and it worked quite well on the AM portion of the ham two meter band.  I talked to many hams on two meter AM with this unit but still, I wanted an FM base station.

 Then I discovered the use of ‘slope detection’.  Typically, when receiving an AM signal you tune the receiver to the center of the carrier.  If the receiver has an S-meter you would tune for the highest indication on the meter.  With FM, it is the frequency that is varying with modulation and not the amplitude.  With slope detection, you tune the receiver off to one side of the carrier on the “slope” of the signal.  An S-meter would indicate off the maximum indication point.  Slope detection is not ideal for use on FM but it does allow the owner of an AM only receiver to listen to FM transmissions.  Once I had converted my ARC-3 receiver and learned slope detection, I had now had a base station receiver for the local repeater and the stations operating on direct.

Of course, once I was able to listen to the local repeater, I wanted to be able to transmit on FM too.  This required a bit more conversion.  I had already converted my ARC-3 transmitter by building an external power supply, added a front panel with a microphone input and gain control, and a convenient socket for a crystal.  I’d even removed the barometric microphone control, which automatically turned down the mike gain as the plane got to a higher altitude (I didn’t really think I’d need that).  The transmitter in the ARC-3 sounded great and worked well on AM but that still would not work on the repeater.

When the transmitter was used for AM, I was able to use some older surplus FT-243 crystals but when I did the conversion for FM, I had to add a VFO so I could put the transmitter exactly onto the repeater’s input frequency.  I used an old Heath VF-1 VFO which had a 40 meter position with output in the 7 MHz range.  I only had to retune it a bit to get it to the 8 MHz range which is what the ARC-3 transmitter needed. 

 To use this transmitter on a repeater, the VFO needed slower tuning and a much more precise tuning ability than was needed for its original use on a CW or phone transmitter.  Just turning the VF-1 knob the smallest amount could move the actual VFO frequency by a half KHz. or so.  Since the transmitter multiplied the crystal (or VFO) frequency by 18, that meant it was almost impossible to set the frequency “right on” by hand.  To solve that problem, I mounted a threaded stud in the side of the VFO’s cabinet.  I screwed a long piece of 6/32 all-thread through this stud and mounted a small washer on the internal end and a knob on the outer end.  By turning the knob I could move the washer closer or further away from the frequency determining VFO coil to adjust the frequency exactly.  It was quite easy to move the frequency in very small increments.

 I guess I should describe the tuning process in some more detail because I had to devise a really odd process to set the transmitter on frequency.  I had built my transmitter power supply as a dual voltage unit controlled with a push-button switch in the front.  When the switch was pushed once I had low voltage (and power), pushed again and I had high voltage (and power).  When the transmitter was operating with the low voltage, the transmitter was actually only putting out a small fraction of a watt and provided a noisy signal into the repeater.  The procedure was, first listen to the repeater, kick the power supply switch (because it was on the floor), and key the transmitter.  By tuning the knob on the side of the VFO I could hear the signal as it passed through the input to the repeater and it would be noisy.  My signal would move from noisy, to quiet, to noisy again. When I was right on frequency, the signal would be quieted and I knew I was right on.  I then kicked the push-button switch and the transmitter would come up to 10 watts and I could carry on my repeater QSO.

 I should mention the additional occasional problem I had with this FM transmitting system.   I had earlier mentioned that the room where my hamshack was located, as well as several other rooms, was served by a wonderful, large air conditioner unit.  The house was an older unit and when the air conditioner would kick on, the voltage in the house would drop a bit which was enough for the VFO to drift off frequency just enough to drop out of the repeater.  Those who knew me and talked with me often knew that when I suddenly dropped out of the repeater, they just needed to wait a bit.  In that time, they knew I would be kicking the power supply to drop the voltage (and power), retuning the knob on the side of the VFO and kicking the power supply to bring it back up to full power.   It actually could be done fairly quickly.   It goes without saying, however, that when the air conditioner unit reached the correct cool temperature, it would kick off, the house voltage would rise enough to change the VFO’s frequency again and I was out of the repeater again.  When I finally was able to graduate to a commercial FM transceiver, it was months before I could keep myself from kicking the wall when the air conditioner went on or off.

 I still needed some way to change my signal from AM to FM.  Someone in the MARS program had come up with a really nifty and easy way to FM the ARC-3 transmitter.  Using a 4-pole double throw switch I was able to put the secondary of the modulation transformer in series with the screen voltage line to the oscillator tube.  The screen bypass capacitor was either removed or made smaller (I don’t remember which now).  It is unbelievable how well this actually worked.  If I modulated too high, it would drive the oscillator out of oscillation and the power would drop so I had to be careful in setting the gain.  The FM audio was actually quite good and I often got compliments on my audio.  I knew of some other MARS members who used the same process on their ARC-3s and they did not have the success that I did.  I used this system for a couple of years.

 I wish I had some pictures of the converted ARC-3 receiver and transmitter but, unfortunately, I was not much into photography during my earlier ham radio days and I just didn’t think to capture some pictures for my ‘golden years.’

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