[AMRadio] Parasitic Suppressors (or lack thereof)

Larry Szendrei ne1s at neandertech.com
Sat Apr 14 16:47:35 EDT 2007

Thanks to everyone who responded to my inquiry concerning the lack of 
parasitic suppressors on old-time PP triode RF PA decks.

The reason I asked, apart from just curiosity, is that my old-buzzard 
plate-modulated PP-812 rig which I put on the air just over a year ago 
had a strange problem where if I load it up too heavily, the audio gets 
weird and actually disappears! The point of "too much loading" is not 
always the same, but is usually between 200 and 300 mA plate current. DC 
grid and plate current seem rock stable, though, even when the 
transmitter is "misbehaving."

Was discussing it with Timtron and he suggested it might be a parasitic 
(not knowing that I had not included suppressors), and I had earlier 
thought this might be a possibility as well.

Long story short - I will retrofit the deck with suppressors as soon as 
my promised nichrome ribbon arrives in the mail.


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