[AMPS] TL-922 Filament Transformer Protection

[Tom Rauch]

> €  If input contact arcing takes place, transients are fed to the input of
> the amplifier tube.  If these transients stimulate intermittent vhf
> oscillations, it doesn't matter if the output relay contacts are closed or
> not since vhf energy can not pass through the low-pass hf tank.  > - 
> cheers, Tom

More typical nonsense and distortion of fact by omission, or else 
you don't understand grounded grid PA circuitry.

Either way, your advice is incorrect.

The input circuit is AFTER the relay and BEFORE the tube. If the 
input circuit is properly designed and implemented, VHF energy 
could never make it to the tube.

Even if there was no input circuit, the tubes have almost no gain at 
VHF when cathode driven. That's because the grid is parallel 
resonant at VHF. Few people use 3-500's as two meter amplifier 
tubes, although they can be used as TPTG oscillators at 180 MHz.

Finally, the VHF energy from the small arc on the input contacts 
would never be large. VHF energy would have to be many many 
times less than the HF energy.


73, Tom W8JI
w8ji@contesting.com

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