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Re: [Amps] Ferrite Core for 160M PI Output ?

To: "'JC'" <>
Subject: Re: [Amps] Ferrite Core for 160M PI Output ?
From: "Peter Voelpel" <>
Date: Tue, 13 Jun 2017 19:41:16 +0200
List-post: <>
Yes, I know.

He used a relative low Q parallel tank circuit on 136kHz.
Output was about 2KW.

Peter, DJ7WW

-----Original Message-----
From: JC [] 
Sent: Dienstag, 13. Juni 2017 18:11
To: 'Peter Voelpel'; 'Chris Wilson';
Subject: RE: [Amps] Ferrite Core for 160M PI Output ?

Hi Peter

PI network loss is related with the Q of the inductor, you need material #2
or #6 ( better stability with temperature), #61 #77 are good for BALUN or
chokes and not good for inductors with high Q.


-----Original Message-----
From: Amps [] On Behalf Of Peter Voelpel
Sent: Tuesday, June 13, 2017 11:28 AM
To: 'Chris Wilson' <>;
Subject: Re: [Amps] Ferrite Core for 160M PI Output ?

Hi Chris,

The builder and owner of the amp is sk, so I don´t know if the amp is still
in use.
But when he built it we where in close contact and I suggested the cores to
The material is close to mix 61, their diameter is 120mm and the thickness
is 15mm, he used a stack of three.
The tape wrapping is only necessary to break the very sharp edges of the
cores, they are not as smooth as the Fire-Rite cores.
Electrically it is not necessary, the do not conduct.

The cores are from ex GDR military sources which more or less dried out.
Dirt cheap they were sold on flea markets for 1,-DM each at the beginning.
The last 50 I bought in 2005 were 2.50 Euro each.

-----Original Message-----
From: Amps [] On Behalf Of Chris Wilson

Hello Peter,

Thanks  for  the photos of the LF tube amp, is there any more info on it
available anywhere? My friend speaks fluent German if it's in that language.

Just  how  conductive *IS* ferrite anyway, i have never probed it. And how
much  of an adavatage is there in stcking cores which are totally flat  on
the  sides which mate together when stacked compared to some that  have  a
bevelled (radiused) surface? i have some FT240-78 cores that all came from
FairRite but some are flat, some bevelled....


On Tuesday, June 13, 2017,  you wrote:

> When I use multiple cores I glue them together with two component 
> epoxy first and then I insulate and wind them, much easier.

> 73
> Peter

Best regards,

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