The FM crystal controlled Transmitter Circuit Pro-096E shown below has an unusual and strange history. Another one of my designs, it is an offshoot of the Pro-033a but it came about in a strange way. I attempted to get this unit FCC approved – nice piece of work, low harmonics, met all the guidelines and underwent trials using my own FCC Approved 3 meter test unit. Attempts were unrelenting and useless in the end and would have cost thousands of dollars to fight an unfightable system to put it in the market.
I simply sent the design overseas to an associate who manufactured it, and it wound back up in the US and in the hands of the very agencies that needed this kind of device, less any static nor involved in or applied to the “RULES” since it was an import.
The design originally was manufactured with a small 6V flat pack battery and if you were a fed back in those days you would remember it. I took this same design, the pro-096E fm crystal controlled transmitter circuit plus a few changes on the rf end due to the drop from 9V to 6V and incorporated a small Duracell PX28l battery which was round and very small and you could purchase battery holders for it rather than use the original flat pack since at that time the holders had to be custom made.
I have scanned the original and functional prototype and it’s circuit is shown below. The Coil forms are Digi-Key fiber washers and I have listed the part number and a photo to show how they are wound below. The turns required are shown on the schematic. Just keep the turns tight next to each other. The crystal is a series cut , 5th overtone cut to exactly 1/2 of your desired frequency output. Enjoy, John