Allison,
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Been looking at what the AM guys are up to as you may have noticed by the links given in my previous posts.
That's exactly what we need for polar SSB, an efficient switch mode RF amp plus a clean and efficient modulator.
Most any of those high powered AM designs on the web could be adapted for use with?
something like the QMX, replacing the last page of the QMX schematics.
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If we have a modulator that has good power supply rejection and feed it from
the HV DC in a discarded PC power supply, could be cheap indeed.?
Kind of janky, but could be made less dangerous than a tube rig with 1kv plate voltages.
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Looked a little further at cheap GaN-FET"s from Innoscience.
Most of the sellers are hawking the INN650D02, Qg down at 1nC, JCLPCB price of $1.33
The INN650DA04 has even lower capacitances, JCLPCB price of $0.37, but package is even smaller.
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Fortunately, Innoscience is targeting wall warts where the cheaper the better.
Unfortunately they are targeting wall warts where the smaller the better.
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Jerry, KE7ER
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On Mon, May 26, 2025 at 11:00 AM, ajparent1/kb1gmx wrote:
For class D or E gan and SiC are high performing.
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BUT... you have to do polar (QMX) to get to SSB or?
like a bunch around here AM.
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Turns out AM is easy, A PWM modulator driving class E or D
output stage.? Most use class E and output power of 385W
carrier for 1500W PEP at 100% modulated.? Impressive
very high quality signals .
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A push pull class D? would be interesting but the amplitude
modulator has to be equally robust and efficient (PWM).
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Work I did, efficiencies or 96% were done and better is
possible.? ?At low power the MPU and other supporting
circuits? contribute to power used and not directly to
RF out.? But 50-60% DC in to RF out is easy.?
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Compare that to IC7300 TX at 22A @13V (280W) for 100w out.
Dial it back to 20W out and you are still pulling about 7A or 91W.
Its not that the finals are inefficient but you have drivers,
DSP, display, and so on all using power.
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It would be attention grabbing.
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--
Allison
