The last tetrode amp of any significance I built was almost half a century
ago. Used an 813 in class C.
The texts at the time made much of the role of the screen in the possible
production of VHF parasitics. Various fixes based mainly on crude empiricism
were offered. Amongst those suggested was running the screen feed in
shielded wire. Presumably one effect of this would be better VHF bypassing,
as the bypass capacitors used at the time were a bit suspect at VHF. Hence I
am not surprised to hear that a fix of a presumably VHF parasite was
achieved as described. (e.g. See pps 22.9-10, Orr, W.I. , Radio Handbook
19th edn 1975)
cheers
end
Barry Kirkwood PhD ZL1DD
Signal Hill Homestay
66 Cory Road
Palm Beach
Waiheke Island 1240
NEW ZEALAND
www.waiheke.co.nz/signal.htm
----- Original Message -----
From: Tom Rauch <w8ji@contesting.com>
To: Peter Sundberg <sm2cew@telia.com>
Cc: <amps@contesting.com>
Sent: Saturday, 20 January, 2001 9:23 AM
Subject: RE: [AMPS] Clipperton L amplifier
>
> > When rebuilding the screen supply for my amp I suddenly developed
> > arcing BIG time in the tank circuit something that had never happened
> > before. Screening the rectifiers and bypassing the cable feeding the
> > screen stopped all arcing. No changes what so ever were done in the
> > tank circuit to stop arcing.
> >
> > There is no doubt in my mind that parasitics caused the tank arcing.
> >
> > 73/Peter SM2CEW
>
> Hi Peter,
>
> I'm missing something.
>
> Are you actually telling us you had a parasitic in your screen
> supply wiring and rectifiers? Please tell us why you think it was a
> parasitic, and what frequency it was on.
>
>
> 73, Tom W8JI
> w8ji@contesting.com
>
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