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[AMPS] neutralization

To: <amps@contesting.com>
Subject: [AMPS] neutralization
From: measures@vc.net (Rich Measures)
Date: Sun, 18 May 97 23:02:01 -0700
>Rich Measures wrote:
>>  
>>This circuit is not found in *Care and Feeding of Power Grid Tubes*.     
>
>So? 
>
>If it isn't in "C&F" or some other 30-year-old publication, does that
>mean that it can't exist or can't be correct? A few new things have
>happened since then.
IMO, the laws of physics do not change substantively.  For example, 'Cold 
Fusion' doesn't.
>
>> I liked Ian White's comment that, due to phase shift, every 
>>negative-feedback [neutralization] circuit (at the fundamental frequency) 
>>becomes a positive-feedback [regeneration] circuit at some higher 
>>frequency.   
>
>No, not "some higher frequency": I said "some DIFFERENT frequency".
>My own main concern is with VHF/UHF amps that need to be stabilized on
>LOWER frequencies. It just shows that you have to consider each case
>very carefully on its own merits.
As long as capacitive reactance decreases with frequency and capacitive 
susceptance increases with frequency, the chance of parasitic 
oscillations on lower frequencies seems a bit unlikely to me.  How many 
amplifiers do we see with VLF suppressors?  
>I still have to smile about the alleged damage caused by VHF
>oscillations to tubes such as the 3CX800 and 8877, which will happily
>pump out 1kW or more in amplifiers for 50, 144, 220 and even 432MHz.
In a VHF amplifier, there is one resonant circuit connected to the 
anode--i.e., the VHF tank itself.  However, in an HF amplifier, two 
resonant circuits are connected to the anode.  One circuit is 
HF-resonant.  The other circuit is VHF-resonant.  This can be checked out 
yourself with a dipmeter, Ian.  If you find that I am in error, please 
publish your findings here.   Too bad you don't live a bit closer.  I 
have a decapitated 8877 on the shelf that--when viewed under a 
microscope--provides a pretty good example of early-stage gold 
sputtering.  There are five areas of gold pooling and a number of gold 
blisters on the grid that have burst their tops and strewn gold 
melt-balls about the cathode--as Eimacs' Mr. Foote described.  
And.........if you get smiled-out on that one, I have another gold 
sputtered 8877 in the garage that WE can decapitate and examine for 
another round of laughs.
Rich---

R. L. Measures, 805-386-3734, AG6K   


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