Last time I had this happen it was the antenna. I think something was
getting hot and changing the match. I am sure you are tuning it into a
dummy load, so it can't be that. However, it was possibly worth
mentioning.
> Mike
Good Idea, Mike,
Try using a crossed needle Wattmeter/SWR meter to watch how/if the SWR changes
in sync with the power drop.
Also observe the plate CURRENT meter at the same time.
All the Best, 73,
Pat Barthelow aa6eg@hotmail.com
http://www.jamesburgdish.org
Subscribe: http://bambi.net/jamesburg.html
Jamesburg Earth Station Moon Bounce Team
> Date: Sat, 29 Sep 2007 22:06:48 +0100
> From: m.j.willis@rl.ac.uk
> To: amps@contesting.com
> Subject: Re: [Amps] HF amp output power dropping
>
> >> HAM use by someone else. It runs a 3CX3000A7 tube in
> >> grounded grid.
> >> Recently the output power has begun falling off rapidly
> >> whenever I apply constant drive such as during tune up.
> >> The tube is new and the plate voltage remains steady as
> >> always.Is there anything else that could be causing this?
> >> It reminds me of a tube that has gone soft although I am
> >> sure it's not the tube.
> >> Any help is appreciated
> >>
> >
> Last time I had this happen it was the antenna. I think something was
> getting hot and changing the match. I am sure you are tuning it into a dummy
> load, so it can't be that. However, it was possibly worth mentioning.
> Mike
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