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{SNIP}

I have a question regarding what appears to be an added 47pF/3kV blue ceramic capacitor in the output tank circuit. It goes from the output contact of the bandswitch to ground, as seen below.

{SNIP}

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Dear Alek,

There is a veritable “no-nonsense” test for your question.

You should do either an “S11,” or an “S21” test with a

Vector Network Analyzer, like the ever-popular

NanoVNA as seen on Ebay or Amazon, etc.

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Dialing-in the Start Frequency (more than likely 1.0 MHz),

and the Stop Frequency, (again, more than likely 30.0MHz),

look at the graph displaying the Reflected Power curve,

and when you have it in front of you, clip the blue cap

and see what it does, For Your Amp.

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Of course, no power in the amp needed. A test clip on the input

and on the output of the tank will suffice.

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My friend AB2NI uses his Nano’ on all the various amplifiers

he’s attempting to renovate, and has uncovered mistunings because

of incorrect padding, incorrect choking, incorrect input tuning, etc.,

and has become astute with the small instrument enough to now

use it as easily as a DMM.

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I am still training for operating knowledge on my VNA. It came

with clips and a small PCB with bits so I could set the machine up

and duplicate the various curves the I/M sez it should.

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I hope this suggestion helps!

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Hal Mandel

W4HBM

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