>The most stable tubes are those with the highest operating
>frequency limits.
>
>73 Tom
_____________________
Old time home brewers will remember the 6AG7. I think the max frequency for
full ratings is something like 10 MHz (whoops it was Mc). They are one of the
worst offenders I have ever met at parasitic oscillations. Used in the Central
Electronics rigs, they needed resistors across the tank coils. Even then, they
would still take off.
As a kid, and not knowing what I was doing, I tried parasitic suppressors in
the cathode, screen grid, control grid and plate - sometimes all at the same
time. By the time I got one stabilized, I was down to 1 watt output. If you
could get one of those tamed, the 811 and 812s were easy.
Colin K7FM
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