>
>Interesting Peter,
>
>> I recently put a new diode rectifier board for the screen voltage supply
>> in my HF amp. I put it in the 'input' compartment of the amplifier and was
>> a little careless not to put the board in the screened box as I wanted to
>> get more room there and get rid of the box. The amp immediately started
>> arcing the bandswitch, BIG time. Most arcing was done between the 15 and
>> 10 meter taps. It has never done this before so I was a bit puzzled. I
>> could not tame the thing on any band, arcing was bad no matter what.
>> Measured voltages, looked all right. Put the box back, screended the diode
>> board and .. Voila, no arcing in the bandswitch. Voltages exactly the same
>> as before.
>
>HF oscillations and instability will cause arcing, VHF oscillations
>however is the topic here.
>
>VHF oscillations will not arc bandswitches because they are
>shunted to ground by the low reactance of the tuning cap.
? As I recall, during the grate parasitics debate, Mr Rauch disclosed
that had measured self-resonances in Tune-caps that were in the 100 to
200 MHz range.
>It is impossible to develop enough VHF voltage across the tuning cap to
>make it, or the bandswitch, arc.
>
>So while I agree you might have had a HF or VLF oscillation that
>made a component arc, the likelihood a VHF parasitic damaged
>anything is very remote.
>
>Of course it is possible if you used a tuning cap that had a very
>high reactance at VHF.....but then your amp would also be a
>harmonic nightmare.
>
>To date, I have never seen a VHF parasitic cause any of the
>problem Rich claims. Even when intentionally created.
>
>
>73, Tom W8JI
>w8ji@contesting.com
>
>--
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>
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
--
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