Thanks Rich!

On Sep 17, 4:55*pm, "Rich Klestinez" wrote:
I would not go through the trouble of unbalancing the transformer

I didn't mean to... The idea was to generate two symmetrical and
opposed signals by putting an un-bal transformer between the VXO and a
first push-pull stage made with just two sections, charged with
rebuilding near-square waveforms.

I matched neither driver sections nor MOSFETs,but I did hear that both
can be a bit variable. Apparently the chip drivers are normally used
without equalization (to the surprise of quite a few authours). As for
MOSFETs, I saw several amp designs with a single separate bias
trimmer, or with a single special driver chip, for several devices. I
have separate trimmers, I didn't bother to check if the 1-mA voltage
was the same for both - but I will. That may have helped equalize the
switching point in terms of RF voltage. As for the different on-state
resistance, I guess it's more critical if one has devices in parallel
- in a push-pull a particuarly low resistance device won't hog the
current.

One other thing comes to mind is that with a torrid core at high current and a high frequency, then symmetry of the winding itself is critical.

Yes, I've been extremely careful. Winding is trifilar, twisted, I
took care to have symmetrical twist pitch and winding spacing.

torrid core

Torrid indeed. Now I have a tiny .82 core and thin wire too. At
normal duty cycle all is fine, after 120s keydown one risks minor
burns - but the MOSFETs barely get warm.

Coincidentally, I just got several 10s of feet of Raychem "high
performance" wire after helping assemble a prototype 4-fuel car (3
liquid fuels + plugin recharger). 1.5sqmm, silver plated stranded
copper alloy, thin 600V radiation-crosslinked high temperature
insulator. I've been verbally told the 1/2sqmm variety can carry 30A
(I asked as I worried it would not bear 3.5). I will try it on a
larger core. I already recovered the ferrite of a 1-kW Hi Gain balun,
but I want to see detailed wire specs first. Once stripped, this wire
should do well in hi-Q coils too.