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[Amps] 8877 on 144MHz negative grid current.

Subject: [Amps] 8877 on 144MHz negative grid current.
From: Conrad PA5Y <>
Date: Fri, 13 Jul 2018 21:09:30 +0200
List-post: <>
Hello all.

I have a question on behalf of an Italian friend of mine.

He has 8877 amplifier for 2m and what sounds like some tired tubes. His 'normal' tube is a 3CPX1500. Recently he has noticed that when he tunes for maximum during tuning his grid current meter goes negative. I personally have never seen this on either of the two 8877 amplifiers that I previously ran. He has tried 2 other tubes which do not have this behaviour although they do produce less output than the tube that exhibits negative grid current. So I suppose the simple question is what causes negative grid current on high Mu triode like a 8877? Back bombardment?


Conrad PA5Y
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