Re: Software support Request for Full QSK BITX40

Jerry Gaffke

If the IRF510 gate is driven hard with a square wave, it switches fine at 7mhz and beyond, showing a nice square wave
for drain voltage (0-24v) and drain current with troughs all the way to zero.  That's with a 50 ohm antenna load, supply at 12v.

If the antenna port impedance is 10000 ohms at 7mhz, those drain and antenna port voltages roughly double,
and drain currents are kept fairly small.    I assume the lack of major voltage spikes is because
there remains some drain current in the troughs due perhaps to miller effect capacitance

If the antenna port impedance is 10000 ohms at 7khz, the simulation shows
the kilovolt spikes I'd expect from a flyback transformer.
Quite curious.
But I think I'm ready to start playing with the uBitx, as the push-pull final there should be more predictable.


On Wed, Jan 31, 2018 at 03:32 pm, Jerry Gaffke wrote:
So T7 does indeed behave like a flyback transformer at slow speeds, but at 7mhz the IRF510
stays on to where that coil current always has somewhere to go, T7 behaves more like a forward transformer.

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