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[AMPS] Another angle on cathode-matching ckts

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Subject: [AMPS] Another angle on cathode-matching ckts
From: (Scott Townley)
Date: Fri, 12 Feb 1999 18:09:12
I've followed the thread on cathode-driven input networks using toroids,
and the general advise that coax between the "tank" and tube filaments is a
bad thing.
Although I have not seen a great many amps in my day, the few I have always
"pigtail" the coax connectorization inside the amp at all.  It
would seem to me (and I've measured it as well) that the shield "pigtail"
is poison to achieving good input matches at 21 MHz and above.  Obviously
the introduced inductance would be that much worse at 3rd and 5th harmonic.
My question:  is it really the coax itself that causes such pain in the
input, or is it the lack of proper coax termination?  Would using quality
bulkhead/panel fittings allow for remoting the input network the
traditional 6-12" from the tube filaments?
Just curious...
Scott Townley  
Gilbert, AZ
Collector of:
        Stoddard Aircraft EMI/RFI receivers and accessories
        Big Parts for that Big Linear Amp 
        70's era RF test equipment HP/GR/Tek
        Radio-related technical reference material 1940+ (someday might have useful info!)

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