[Amps] SB-220 parasitic suppressors

[Steve Thompson]

Tony King wrote:
> At 01:21 AM 11/4/2004, R.Measures wrote:
>> <snip>
>> A GS-35b has 0.12pF of anode-cathode feedback C.  An 8877 has 0.10pF
>> of it, so they have a fairly similar amount of internal feedback.
>> Our 8877 low VHF-Q parasitic suppressor retrofit kit has both an
>> anode suppressor and a cathode suppressor.  It comes with a money
>> back guarantee.  So far, the only refund has been to a guy who said
>> he did not know how to solder. --  Today's trivia question:  At its
>> max freq of 1000MHz, what is the reactance in ohms of the
>> output/input feedback path in a (g-g) GS-35b?
>
> Very interesting.  My guess: 1326
Feedback C on the data sheet is almost certainly measured at low frequency.
The feedback characteristics at V/UHF might be different.

By now there's lots of amps out there using the Russian planar triodes. Has
anyone heard of any problems?

Don't forget that oscillation require two conditions: loop gain >1 and
phase=0. Lots of things contribute to both.

Steve