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[AMPS] Loss in doorknob caps?

To: <amps@contesting.com>
Subject: [AMPS] Loss in doorknob caps?
From: 2@vc.net (measures)
Date: Sun, 20 Feb 2000 22:13:03 -0700
>
>I'm shunt feeding my tower for the low bands. When replacing air variables
>caps with fixed doorknobs, the reflected power is much greater. Any
>thoughts on the losses in doorknob caps vs frequency?
>
This problem could be caused by using a bypass type cap in a tuned 
circuit app. . 
There are two kinds of doorknob caps.  .   Bypass / coupling service and 
tuned circuit service.  Typically, the largest value for tuned circuits 
is 200pF at 7500v (type 57).  Most 500pF and 1000pF doorknobs are for 
bypass/coupling and drift way too much for tuned circuits.  In the 
smaller case size, 100pF at 5kV is the largest value for tuned circuit 
use.  

good luck, Steve.  

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