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Re: [Amps] how to wind an HF broadband 10:1 transformer

To: Peter Voelpel <>
Subject: Re: [Amps] how to wind an HF broadband 10:1 transformer
From: Dan Sawyer <>
Date: Sun, 02 Mar 2008 19:06:11 -0800
List-post: <">>

Are you saying number 2, red, and number 6, yellow, material cores are 
not suitable for low power broadband transformers? Or is this a power 
and heating issue that is not relevant at low power?


Peter Voelpel wrote:
> Manfred, total wire lenghts must have been 6-7m.
> I fully agree to all your comments.
> Powered iron core baluns are only suitable for tuned circuits, not for
> wideband use.
> A good example is the 1:4 balun behind a LC tuner to drive an open wire
> feeder for multiband use, there ferrit cores will overheat quickly
> 73
> Peter
> -----Original Message-----
> From: [] On
> Behalf Of Manfred Mornhinweg
> Peter,
>> I did that when I got my copy of V.O.Stokes book many years ago,
>> where I found his wideband transformer concept. Using the largest
>> ferrit toroids I could get, they were similar to Amidon #61, I
>> sandwiched them between 5mm thick aluminum plates 20x10cm for 
>> cooling, used 2x12 toroids and wound a 50:600 transformer with 3mm
>> teflon covered wire to feed my terminated V-Beam from 160-10m. That
>> worked perfectly well with all the power my modified L4B (3.5KV)
>> could deliver.
> The fact that you needed heat sinks makes me think that you ran those 
> ferrites at pretty high flux density. That was probably necessary to get 
> an acceptable wire length. How much wire did you have to wind on these 
> transformers?
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