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Re: [Amps] HV feed through capacitor

To: AMPS <>
Subject: Re: [Amps] HV feed through capacitor
From: Mike Tubby <>
Date: Fri, 10 Feb 2012 21:18:10 +0000
List-post: <">>

At 432MHz you might be able to put a 1/4-wave stub in the HT feed, 
depending where you put the feedthru in the anode chassis, a 13.5cm 
length of RG400 (or similar) PTFE coax grounded at the feedthru end and 
open at the tube/anode end might give you an additional 15-20dB of 
isolation and allow you to use cheaper bypass caps...

Just an idea...

Mike G8TIC

On 10/02/2012 20:34, Larry wrote:
> Carl,
> Yeah, it's for a 432 amp. At that frequency the series inductance of a
> single "normal" disc ceramic is enough to prevent good bypass action.
> Results in a lot more 432 energy running around on the HV line than I like.
> YU1AW calls for a cap made from FR4 PCB material. Even though I etched
> back the edges and hi-potted the thing, it still managed to prove that
> my HV supply fault mitigation system actually works!
> I have some 270 pF/6KV discs that I've been playing with. By cutting off
> the leads and soldering directly to short pieces of 3/8 inch wide copper
> strap and using several in parallel, the network analyzer suggests that
> it might work. I will try that if no reasonable feed through cap shows up.
> Thanks to all those that responded with vendors. Nothing seen so far
> looks suitable for my purpose. BTW, Surplus Sales is #1 on my list of
> "never again" vendors.
> 73, Larry - W7IUV
> On 10-Feb-12 12:04 PM, Carl wrote:
>> Any reason you cant use a ceramic feedthru and a disc cap for bypass?
>> Works for me at the 1500W level thru 222 MHz.
>> Carl
>> KM1H
>> ----- Original Message ----- From: "Larry"<>
>> To: "AMPS"<>
>> Sent: Friday, February 10, 2012 12:25 PM
>> Subject: [Amps] HV feed through capacitor
>>> Can anyone suggest a source of high voltage feed through capacitors. I
>>> need 5 KV minimum and 270 pF to 1000 pF. Any leads to a supplier would
>>> be appreciated.
>>> Thanks&  73,
>>> Larry - W7IUV
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