> >HF g-g amplifiers are quite unlikely to oscillate below
> >the grid resonance. For a 3-500Z, this is c. 80MHz.
>
>
> The original comment was about shielding the screen
> supply...... hardly applicable to 3-500Zs.
It's wrong anyway Peter. As Rich's theories fall apart, he has had
to "make" tubes oscillate lower and lower in frequency.
3-500Z's tend to oscillate above two meters, tubes like 4-1000A's,
3-1000Z's, and 3CX1200A and D7's tend to oscillate near the FM
BCB (100 MHz or so).
572B's tend to take off lower yet in frequency.
Generally speaking the lower the frequency of oscillation, the more
difficult it is to cure the problem and the more likely it is to have
damage.
73, Tom W8JI
w8ji@contesting.com
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