Hi Jim,

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If you detune the front end the reflected or

returned Smith chart will show greatly, yes?

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Only by running the entire amp together is

it possible to get the most bang for buck.

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As many as there are of builders there will

be separate and distinct philosophies about

how to Tune the Whole Thing.

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The problem with using a SpecAn with the amp

going is, as we talked about earlier, dealing with

Sampling Attenuation. If an analyzer’s only rated

at let’s say 15dBm, then hitting it with 13dBm is

still calling it close, but nevertheless the practice

might be the best way to see what’s hiding in them

thar hills.

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I use a stack of Inmet model 2N-3dB N-connector

attenuators on the analyzer Port 1, but also run a

bench DMM with good ability to portray dBm,

because, Jim, I don’t trust anything in RF to not

be lyin’.

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Once the tubes are humming and your exciter is

driving the amp a good sampling pile and your SpecAn

would be perfect. All you need do then is to tweak the

input coils and watch the ‘scope.

Hal

W4HBM

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