[Amps] Parasites (parasitics)

[Merv Schweigert]

>
>
> >
> >> >The question referred to suppressing 100 mHz only.  This can be done
with
> >a
> >> >stub, a series tuned circuit that loads the parasitic at that
frequency,
> >>
> >> **  loading the parasitic after the fact is not possible.  The trick is
> >> to reduce gain at the anode's specific damped-wave ringing frequency.
> >
> >Probably a dumb question.. in 4-1000 amps the "parasitic" or oscillation
> >that occurs was in the 90 or so MHZ region.  It seemed very easy to
> >cure that by moving that "resonant" freq out of the VHF "high gain "
> >region ( or is it called self resonant freq of the tube ?) down to a
lower
> >freq just by inserting a coil of wire in the plate lead.  No resistor
needed
> at
> >all, just keep the "resonance" above 35 MHZ or so, so that it did not
affect
> 10
> >meters.
> >What am I missing that this is not used more ??
>
> **  How much L was added?
> Was it grounded-grid - or grid-driven?
>
Sorry about that .. did not measure the L.. but 3 turns of number
12 wire 1inch diameter is what memory tells me.  Grounded grid.
Eimac plastic sockets.  Was very repeatable in all the amps I built
and several others that had problems.
Covered 160 to 10.. (with a shorting bandswitch a must I must add)
Merv