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Re: [Amps] Neutralizing Dentrons

To: "Tom W8JI" <>
Subject: Re: [Amps] Neutralizing Dentrons
From: R L Measures <>
Date: Sun, 25 Jun 2006 16:21:47 -0700
List-post: <>
On Jun 25, 2006, at 2:55 PM, Tom W8JI wrote:

>> After producing the Warrior and the GSB-201, finding that
>> even though  the RCA Tube Manual's "neutralization"
>> circuit deceased feedback at  HF, due to phase shifting as
>> freq shifted, they came to realize that  it had the
>> opposite effect at VHF, and neither Heath nor Gonset
>> produced another "neutralized" g-g amp.
> Not for the reasons you gave.

So phase shift remains constant no matter how much freq. increases?
> 1.) Heath and Gonset did not make any more four parallel
> tube amps using tubes with high feedthrough capacitance.
> They had no reason to put it in other amps.

Valid point, Tom, but Heath used the 572B in a subsequent amplifier  
and they chose not to use RCA's g-g "neutralization" circuit.  One of  
the first amplifiers I ever installed low-Q suppressors in was a  
squirrelly GSB-201.  Removing the "neutralization" proved to be a  
good move
> 2.) The path for VHF oscillation problems is not back to the
> cathode anyway. The control grid floating at VHF from stray
> C and the long thin inductive grid lead is the problem.

However, since neither the cathode or the grid is at Ov potential at  
VHF. and both have capacitance to the anode, the parasite problem is  
more complex than it may first look.
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R L MEASURES, AG6K. 805-386-3734

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