For that to happen Eddy you have more than a loading problem. Have you ever
looked at the signal on a spectrum analyzer or station monitor?
Id expect some funny stuff would be showing
Carl
KM1H
----- Original Message -----
From: "Eddy Swynar" <deswynar@xplornet.ca>
To: <amps@contesting.com>
Sent: Monday, December 19, 2011 8:32 AM
Subject: [Amps] Linear Amplifier Tuning---PROPERLY!
> Good Day All,
>
> A stupid question to many, no doubt, but one that I'd like some
> clarification on, at long last...
>
> Specifically, anything that I've read in different literature & in on-line
> write-ups regarding the proper tuning of grounded-grid linear RF
> amplifiers makes note of one, final step in the tune-up procedure:
> specifically, one is to reduce the plate loading capacitance (and thereby
> slightly over-couple the amplifier to its load) such that power output is
> lowered by some 5-10%...
>
> Correct?
>
> Yet, nowhere is this instruction followed by anything advising one to
> subsequently "re-peak" the plate tuning capacitor in kind, as I
> instinctively always do (force of habit, I guess).
>
> Is it a requirement to do just that, i.e. to tweak the plate tuning after
> this deliberate over-coupling...? Have the authors of these write-ups
> simply assumed that that is, indeed, the case, & have therefore not made
> specific reference to this process...? Or does one truly advance the
> loading capacitor to lower output---and then leave well enough alone...?
>
> I ask this because I am finding that the tuning requirements of my
> homebrewed 2x813 kilowatt can be VERY exacting: improperly adjusted, & the
> keying from it on CW can sound inordinately hard---almost clicky. I'd like
> to do things right with it, both for the sake of the tubes, as well as for
> others on the band who might be operating close to my frequency...
>
> Thanks in advance,
>
> ~73~ de Eddy VE3CUI - VE3XZ
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