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Re: [Amps] Series C in amp output

To: Bill Turner <>
Subject: Re: [Amps] Series C in amp output
From: Vic Rosenthal <>
Date: Tue, 13 Feb 2018 07:41:49 +0200
List-post: <>
I have always thought those ‘safety’ chokes aren’t worth much. The 2.5 mh 
chokes often used in that spot are rated at 300 or even 125 ma, and I suspect 
they would open long before the plate supply fuses would blow.
But note that the capacitors Martin mentioned are only rated at 500v, so they 
aren’t much of a safety feature either!

Vic 4X6GP 

> On 9 Feb 2018, at 18:58, Bill Turner <> wrote:
> ------------ ORIGINAL MESSAGE ------------(may be snipped)
>> On Fri, 9 Feb 2018 17:06:25 +0700, you wrote:
>> Amps from Acom and OM, maybe some others, have a large amount of 
>> capacitance in series with the output after the power/SWR bridge. In the 
>> case of the Acom 1000 this is 6 parallel 10nF/500v disc ceramic 
>> capacitors with a 1 megohm (static bleed?) across them.
>> Have not seen this configuration on older Alpha amps or others. Can 
>> anyone comment on the purpose?
>> Thanks
>> Martin, HS0ZED
> Just a guess:  It might be a safety issue. In case the plate blocking
> capacitor shorts, it would prevent HV from appearing on the antenna.
> Other amps do this protection with a RF choke across the output of the
> Pi network. In case of a blocking cap short, the fuse(s) would blow.
> 73, Bill W6WRT
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