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Re: [Amps] parasitic suppressor for six meters

To: amps <>
Subject: Re: [Amps] parasitic suppressor for six meters
From: Ron Youvan <>
Date: Mon, 16 Jul 2018 12:21:25 -0400
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On 07/15/2018 10:20 AM, Bill Turner wrote:

I'm thinking
about replacing the two burned resistors with a single 22 ohm 5 Watt metal
film resistor, and trimming the inductor to a single turn. Does this seem a
reasonable change? Does the tube require any parasitic suppressor at all?


Many amps have parasitic suppressors but actually don't heed them at
all, especially if the leads from anode to RF choke and tune cap are
very short. I would try the amp without the suppressor, bringing up
the plate voltage slowly in class AB mode and see if you get lucky. I
have built several amps using an 8877 on HF ( not VHF) without a
suppressor and all were perfectly stable.

I suspect many commercial manufacturers put in a suppressor "just in
case" or because customers want to see one there.

Most broadcast transmitters that I have see or have downloaded the IB for have not used any parasitic suppressor at all. The biggest reason to use any parasitic suppressor is because it is a multi-band amplifier. (on some bands the design is wrong) In a single band amplifier correctly designed and implemented ovoids the necessity for any parasitic suppressor at all.
  Ron  KA4INM - Youvan's corollary:
                Every action results in unwanted side effects.
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