This is the golden age of electronic experimentation.
I can design a PCB in Kicad and have 5 boards built and delivered in a week or two for $5.
Parts for a complete transceiver similar to the Micro-mountaineer can be found online?
for a grand total of maybe $10, along with all the needed datasheets.
A $15 RPi-Zero would run circles around a million dollar Cray 1 for DSP algorithms.
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Communications is no longer problematic in an era of cell phones and email, radio isn't quite so magical.
Many of the experimenters have moved on to DIY audio, electric vehicles, robotics, off-grid power.?
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The big thing in RF power amps these days is Current Mode Class D, or CMCD.
This is considered a further development beyond Class E or Class F, and the subject of numerous MS and PHd theses.
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Curiously enough, it's the AM phone crowd doing much of the experimentation with DIY builds in ham radio.
A CMCD type RF amp with a Class D AM modulator could be easily adapted for use with Hans' Synthesized EER scheme.
The INN650D02's mentioned by KJ7AGO in that final web link above are $1 on Aliexpress, I've got 20 getting shipped this way.
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Around 1970, an aging ham gifted me with his junk box.
Included some Ford coils with which to build a spark gap transmitter.
(Scary to think that he was younger than I am now.)
Also a 2kv 2kW plate transformer and a couple dozen 810 triodes.
Still have the 810's down in the basement, and occasionally consider building this push-pull amp:
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Curiously, that 810 design from 1938 has the topology of a Current Mode Class D amplifier.
There are published examples of that design dating back to about 1930.
This 1934 guide for amateurs has many different CMCD style designs.
Those guys knew what worked, and I'm sure they fiddled with drive levels and? tank circuit C,L values
till they got maximum efficiency.? ?Which would put it in CMCD mode with ZVS.
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Jerry, KE7ER
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On Sat, Feb 22, 2025 at 07:38 AM, bill K7WXW wrote:
I don’t know, Jerry, maybe not the norm, but a significant proportion of hams built their own gear back then. “Solid state design for the radio amateur” sold more than 50,000 copies, the ARRL handbook was filled with practical projects and a reasonable amount of electronic and RF theory, and there were still lots of local places to buy parts. I was a digital design engineer in those days, and did RF stuff when I got tired of zeros and ones.
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Or maybe my nostalgia for the golden years of DIY PCBs, ECL and 40763s, leaded components, and deadbugging continue to get the better of me. :)
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bill K7WXW
David Wilcox K8WPE