Has anyone tried lining the input or output cavities of PAs with the
"lossy" material used in anechioc chambers to suppress RF reflections?
The effect is to reduce the "Q" of the cavity, so that instead of
reducing the series "Q", as applied in nichrome wire transmission leads,
etc.(and which might reduce power slightly by introducing series loss in
the tuned circuit), the overall cavity "Q" is reduced, thus greatly
damping any oscillatory tendencies. If this works, the reduction in "Q"
is free/lossless.
This technique is highly effective is stabilising pre-amps with a
tendency to oscillate.
Ian ZS6BTE
> . One problem with conducting such a test is that parasites do not
> always cooperate. However, with a sample/hold spectrum-analyzer, it
> would be possible to show that the amplitude of damped-wave VHF ringing
> in the anode-circuit of a HF amplifier is reduced by decreasing VHF-Q.
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