Shawn Tayler wrote:
> I have done just the opposite direct for this test, injecting the signal
> on the output and watching the level in the input.
If the tube is off (as it was when this was done), and there are no
magnetic devices like isolators, I don't see what difference it would
make. The system would be a reciprocal two-port so you should get the
same result in either direction.
To do it while the tube is on would be another matter. Perhaps we should
have made a cheap sensitive RF source and detector for this - putting a
spectrum analyser on the input and a tracking generator on the output
when the amp was on would have been brave to say the least!
> I would adjust the
> input and output tunning for maximum coupling then the neutralization
> adjustment for minimum, watch to keep the loss > 10dB better than the
> expected stage gain.
We did adjust tuning & loading to get the maximum coupling, and
neutrilisation for minimum. This was checked with a spectrum analyser,
so it was not checked at only one frequency, but swept.
It's a long long time ago I last looked at this, but I don't think the
neutrilation was really necessary. The isolation was so much more than
the stage gain.
--
David Kirkby,
G8WRB
Please check out http://www.g8wrb.org/
of if you live in Essex http://www.southminster-branch-line.org.uk/
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