NEW Tx, Push Pull Class E

[stretchy]

Latest incarnation from my bench, actually the kitchen table at the mo'!

A Push Pull class E design ANY frequency up to 8MHz.

Will work from 12V to whatever.

Keeping it sensible I'm getting 25W carrier at 12V and just under 100W at 24V.

Has my MiNi PWM to the LHS, the filter sits on top, will mod 200W!

I've only got 3 PCB's made, want one built up? let me know.

Stretchy.

[HighMountainRadio]

Greetings Stretchy !

VERY cool indeed !! Just saw your post here..

73... Spooky...

[Kage]

After I played around with Class E designs recently I have to admit it makes almost no sense not to go this route given the efficiency and simplicity.

Currently I'm building a simple medium wave transmitter using the famous 4046 PLL. 4060 clock generator, and 40103 down counter to select transmit frequency via DIP switches. The schematic for that chip combo is widely spread on the web so no need to link it here.
All that is needed after that point is a current buffer and the MOSFET(s) and with the right output network you either have a Class E or D transmitter with nothing more than a small handful of parts. Split the square wave input phase and double the PLL frequency and you can run MOSFETs in push-pull if wanted.
The space that this requires is so small it's almost laughable. The power supply will be the biggest part of the whole project!
Modulation can be implemented with an all in one modern class D amplifier chip to even further cut down the size and increase efficiency.

I'm kind of stunned that I ever considered designing a transmitter any other way, unless I feel nostalgic and want to go with tubes or something.
Designing the PLL to get up to shortwave frequencies isn't very hard to do either, just need a fast modern CD4046 like the ones from TI that can easily get up to the frequencies you want and maybe one more 40103 or a different IC to accept something more than 8bit down counting and use the 4060 at 5kHz instead of 10kHz to get 5kHz channel spacing.
Of course there are plenty of other more sophisticated PLL driver designs, but the idea is to drive that MOSFET with a square and it can't possibly get any simpler or neat.

It wouldn't surprise me if most of the modern transceivers that come in very small packages (like that Anytone Smart CB) use class E output because very few other designs could fit in that amount of space and generate any reputable amount of power.