In this letter, the author responds to the story “Double-Hop Dreams and the Mystery of Long-Distance FM.” Radio World welcomes letters to the editor on this or any story. Email [email protected].
Thanks for a great article.
I was in school, possibly the seventh grade, in 1956—57. Not having any money, and as not many jobs were available for kids, my only personal radio was a crystal set. I was introduced to electronics by my older brother Johnny.
He was attending an electronics school and I followed his interest. Not knowing any theory at the time, I would try different ways of building crystal sets.
One hot summer evening, I was in our attic area and wound a random coil, a 1N34 Diode and a random variable capacitor. Once I connected a long wire horizontal antenna, about 40-ft. long. I could very faintly hear a signal that would fade in and out. A fading signal on a crystal set just gets quieter — no noise level like normal radios.
I suspected it to be a distant shortwave signal, but from where?
I had a V-M tape recorder with a microphone input. I connected the crystal set to its mic input, and on its speaker, the station became easily audible.
It was HCJB(AM) in Quito, Ecuador!
To this day I have a fondness for crystal sets, or memories.
In my bedroom, shared with my brother Johnny, I had a fixed crystal set in a cigar box, hung on my metal bed frame — I used our copper gutters as my antenna and a gas pipe as my ground!
Twenty-four hours a day I could listen to WEOA(AM), which was approximately 1.5 miles away — with no batteries required! I was able to get enough signal that I was able to use a speaker output transformer, that was for a 50C5 Tube, that it would drive a four-inch four-ohm speaker to a low level. No amplifier was used. This same crystal set also let me hear to XERF(AM) in Mexico every night, but because of the “Q” of my rudimentary Coil and capacitor tuning, other stations on either side of XERF were also heard, making listening to XERF not enjoyable.
I then fooled around with trying to receive an FM station that was about 2 miles away, WIKY. Back then, FM stations only used horizontal polarity. For an antenna, I used our outside 2-bay Conical TV Antenna, which barely provided enough audio for my earphone. So, I again used the V-M tape recorder’s mic input to bring it to a listening level. I didn’t know at the time why it tuned as it did — tuning it was different than expected and later I knew why.
Using an AM detector when recovering audio from an FM signal works on the “slope detection” principle. It was necessary to tune the crystal set to slightly above or slightly below the carrier’s center frequency. If you tuned the crystal set to the station’s center frequency no audio is recovered.
You are likely familiar with “slope detection,” but at that time I didn’t understand why it tuned in such a strange way.
Sorry for rambling on, but your article made me relive my childhood and I thank you for that! Growing up in the 1950’s was great and others should envy those of us who were blessed enough to have enjoyed it all.
Although I am 81 now, my son Dave and I continue to build and service radio and TV stations. Dave now does most of the field work and I do bench service and field measurements.
— Frank Hertel, Evansville, Ind.
[Read the Signal Spot from Nick Langan for More DX-Related Stories]
