My First Home Built Radio
Recognizing my early interest in short wave radio, my Dad encouraged me to build a regenerative receiver. The project was featured in the 1953 ARRL Handbook and in 1954 we spent many hours together building the receiver and trying to get it to work. It never did. About fifty years later looking through some storage boxes, I found the radio and soon determined that it had always worked, but due to an error, I’d used the wrong headphones to listen to signals! Therein rests an interesting story about my Dad and me building this radio..
In 1954 My Dad and I built the 6SN7 "One Tube Regenerative Receiver" that is described in the 1953 ARRL Handbook(HB). The article begins on page 104.
I was 13 years old at the time. Dad and I worked hard getting the components (transformers, coil forms, capacitors, resistors, tubes, wire, solder, etc) to build that receiver. As I recall we purchased them from places like Allied Radio and Burstein-Applebee. It was clear to me from the beginning that my Dad took it as a personal challenge to get the radio built ... and working.
One component, C1 -- the adjustable condenser that provides capacitance between the antenna and the top end of the antenna coil -- had to be built from scratch. And it was a big challenge. C1 is made from two 1" squares of sheet copper. One plate is on insulated posts mounted on the chassis. The other plate is secured to a 1/4" round polystyrene rod that extends from the rear of the chassis to and through the front panel where the knob is attached. It sounds simple. But I recall it took us many days to get C-1 to rotate properly and for both plates to mate correctly.
As you all know, many popular regenerative circuits that use headphones have them in series with the B+ source to the AF output. And that is true of the radio we built. Not a problem, I had an almost new set of Army Surplus headphones that were popular in that era. And they looked insulated well enough to handle the voltages that powered this receiver. I think I paid $2.95 for them, and to me that was a lot of money back in those days.
I built the power supply on a separate chassis -- using the slat wood chassis approach. After it was built, I checked the output voltage with my Dad’s EICO VOM and found it to be, IIRC, about 185 volts VDC. So the P/S was working just fine. And the P/S looked pretty much like the photo on page 106 of the Handbook.
Well my Dad and I worked and worked on that regenerative radio. All of the point to point wiring was done with 18 gauge square and round buss wire. So once a connection was soldered --it was firmly and solidly in place.
Finally the radio is completely wired and ready for a trial run. Now I have to say that from the outside, the finished radio looked very much like the photo of the ARRL’s version of the radio on page 104 of the '53 HB – complete with the large dial and knobs. After checking our work several times, we fired up the radio. No signals; no joy. Rechecked the circuit several times. No signals;no joy.
Dad wrote the ARRL and asked for help. They replied with some suggestions. One of which was to connect a resistor from one side of the filaments to ground. (I do not remember what purpose this resistor serves. If you do, please let me know.) Anyway still no joy. We tried again and again to get the radio to work ... and it just wouldn't play.
Several months go by ... and by then I had my ham ticket, licensed as KN4ADR, a Heathkit AT-1 transmitter, an AC-1 antenna coupler and a Hallicrafters S-38-C receiver. I was totally immersed virtually every day after school in contacting hams all over the Eastern United States using morse code. So of course the regenerative radio was stored and forgotten.
About fifty years later I'm unpacking some boxes of my old radio stuff. And there it is: the forgotten, old 6SN7 regenerative radio that my Dad and I built when I was 13 years old. It is now dusty, dirty and laden with grime. The 6SN7 vacuum tube is still in the octal socket. As is the antenna coil I'd wound; it was still in the 5-pin socket. Hmmm, wonder if I can get this radio to work?
Well this time a couple of things are different. I'm older and a little more experienced with and knowledgeable about radios. I have many Radio Shack solid state (SS) monaural AF amplifiers that I use to listen to my R-390A radios, and therefore I don't use headphones much anymore.
Reading a few regenerative radio articles, I quickly find out that I can use my SS AF amplifier instead of the earphones -- if I bridge the headphone jacks with a 10,000 ohm resistor, and connect my SS amp via a .01 cap to the jack that connects to pin 2 of the 6SN7.
So I find a suitable power supply(P/S) for the radio, wire in the parts and connect theamp and antenna. I turn on the AF amp, P/S and the radio. Then I couldn't believe my ears. For the first time in 50 years, I hear static coming from the speaker! Which means the radio may actually work! I turn up the volume on the AF amp. More static!
I turn the regen control to a point where I hear a lot of static and a slight squeal indicating the receiver is going into its proper regenerative mode. Then I alternately adjust the antenna trimmer control, C1, and tune the band set and bandspread condensers looking for radio signals among all that static. Within a few iterations, I hear a radio station on the speaker. I grin from ear to ear. And want to yell a big whoop and holler, but then thought I'd better not. Lest my wife think I'm going over the edge, which she probably suspects anyway given how much time I spend messing around with ham radio gear.
Anyway ... I tune the radio some more, fiddle with C-1, and find more stations. I cannot begin to describe the excitement thatI felt at that point .. and the sadness. Excitement that the radio my Dad and I had worked so hard on 50 years ago works after all.
And sadness in that my Dad passed away many years ago and therefore he wasn't able to enjoy the same pleasure and excitement of hearing our first home-built radio actually work. He would have been pleased and excited to hear the good news, I'm sure.
Building that radio was a big deal for us 50 years ago and I still have fond memories of the experience. I also have some regret. I recall giving my Dad a hard time about why he couldn't get the radio to work. (As a little kid, of course, I assumed it was all his responsibility...). I feel very bad now about teasing him and needling him that way.
My Dad was a pretty amazing guy when it came to repairing and building all kinds of things. He successfully tackled projects involving carpentry, woodworking -- making tables, beds and stools, turning wooden bowls and lamps using a lathe, repairing oil burner furnaces, tobacco barn furnaces, doing electrical and plumbing repairs ... and on and on.
In the 1930's, to learn more about how an automobile worked, he and his best friend, Haywood Edmundson disassembled a Chevrolet -- engine and all -- and then completely rebuilt the car! Amazingly, I'm told, there wereno parts left over!
But back to radios. In his teenage years, he also built several regenerative radios somewhat similar to the one we were building. So ... among his friends and family, my Dad was a well known and respected "Mr. Fixit".
Now as far as I remember, that little Regenerative radio we built is the only thing he ever touched -- that didn't work afterwards. (And the reason it didn't work? Well it wasn't anything he did. It was my error as I explain in the next paragraph.)
Why didn't the 6SN7 regenerative radio work 50 years ago? Because those new Army headphones I used were low impedance HS-33's. Somehow back then I didn't know or didn't remember that HS-33's were low impedance. Or dismissed the clear instructions in the last paragraph on page 106 of the HB which says: "to avoid the (use of) "low impedance" headphones offered in many of the surplus outlets."
So it was my fault our radio didn't work. And now I hope this little story and my admitting fault might atone a little bit for the needling I gave my Dad. I'm sure he's up there in that big radio room in the sky saying: "Now you see, son, I told you that radio would work. And it does. It just took 50 years to prove it!".