> Another possible reason for the 220pF grid to ground in the 30L1 comes to
> mind. 220pF and 125 nH resonate about 30MHz. The grid structure inductance
> plus socket plus capacitor lead length could just about reach this value,
> so is it possible that there was an intention to series resonate the grid
> inductance at 30MHz to improve stability by 'better' grounding of the grid
> in each 811?
>
> Just a thought as to how it happened, not a defence of the
If you look at the series of "production changes" and field mods to
the 30L1, plus their suggestion of using a long cable to the exciter,
it appears they were somewhat unsuccessful at making the
amplifier stable on ten meters....if that was the trick they were
using.
All lifting the grid through a capacitor does is move stability
problems to a lower frequency and a higher frequency...on both
sides of the sharp dip in impedance created by the additional
component.
73, Tom W8JI
w8ji@contesting.com
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