Today I did three things:
1.) Added a safety choke to ground on output side of pi network. Of
course it should have been there all along.
2.) Added a .01 uF cap across the filament pins.
3.) Upgraded the bypass at the cold end of the plate choke from 1000
pF to 4700 pF.
No change in LF parasitic. In fact the LF energy almost cooked the
safety choke. That choke gets hot fast with 400 kHz RF floating around!
I have ordered a supply of .01 and .1 uF bypass caps which I will
distribute liberally. But I still don't understand why this thing is
taking off at LF.
Did I mention that once it starts oscillating at LF, it locks itself
into transmit mode and will not switch to receive? This LF just gets
into everything. Hopefully better bypassing will help with that, but
I'm not convinced it will prevent the oscillation. I must be missing
something here.
73
--
Paul Kelley, N1BUG
RFI Committee chair,
Piscataquis Amateur Radio Club
http://www.k1pq.org
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