@llorenzin @mbroome
Some of us autistic folks are good at tech stuff including deep-dive R&D and experimentation.
Construction of all my transmitters was based on and updated from 1960's amateur(ham) radio practice. To get the frequency stability needed in the FM broacsst band I basically reversed the layout of superheterodyne receivera with VFO (variable oacillator) tuning. The low oscillator in the range around 7 MHZ depending on final frequency was modulated wirh opposing ordinary diodes acting as a varacter. The high oscillator was a 3x ovwrtone crystal oscillator at 27 or 32 mhz depending on available crystals.
The high oscillator went to a tripler and the low oscillator to a buffer stage to isolate it from the mixer. Outputs of these went to the mixer, taking sum or difference depending on crystal to give at first 87.9 and later 88.1 MHZ.
A critically tuned mixer output and similar highly selective amplifier stages picked out the desired frequency and blocked the other mixer products. This in fact wad the hardest part of the design, as a bad choice of crystal and final output could put undesired mixer products too close to the intended frequency to filter out.
The common diode ring doubly balanced mixer design did not give a clean enough output. What worked was a singally balanced active mixer wirh a pair of transistors. Low oscillator in push-pull, high oscillator in parallel so the push-pull output tuned circuit would not pass much of it.
Finally came that tube driver and dual 6146B push-pull power amp in tje 1995-1996 "Generation 10" design, and in later portable rigs big VHF bipolar power transistors. The tube setup at first made a very inefficient 40-50 watts wirh 440V from a guitar amp transformer (bottoming voltage too high), then with a bit over 500V and some tank circuit work ultimately made about 100W.
The portable setups were used from the woods on battery power, wirh a 2 half waves in phase antenna pulled 80 feet up a tree wirh a halyard sent up via slingshot.This was after l ran out of fixed base locations.
All broadcasts were under the callsign "WSQT" or "the squat" on literally squatted Rf spectrum.
