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Re: [TenTec] [Fwd: Line Isolator Balun (sorta) question.]

To: tentec@contesting.com
Subject: Re: [TenTec] [Fwd: Line Isolator Balun (sorta) question.]
From: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Reply-to: geraldj@weather.net, Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Fri, 06 Aug 2010 17:20:42 -0500
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
I guess I'm using the term "beads" a bit figuratively taking into 
account toroids big enough to pass a coax connector on RG-213. For HF 
choking they need an initial permeability of a few hundred to 1200 or 
so. For a transformer that permeability for HF would be 50 or 125. Its 
really hard to put multiple turns of RG-213 through any size of toroid.

Yes on the basis of the least cost of ferrite, a chunk of teflon coax 
winds on ONE large toroid to make a decent choke, but that teflon coax 
gets warm at 1200 watts or more.

Snap on RFI toroids are in the same region of sizes, but the potential 
for a lowered effective permeability due to the airgap at assembly is a 
significant problem.

73, Jerry, K0CQ

On 8/6/2010 1:15 PM, Jim Brown K9YC wrote:
> On Fri, 06 Aug 2010 12:43:30 -0500, Dr. Gerald N. Johnson wrote:
>
>> That depends a great deal on the ferrite mix. There are beads suitable
>> for HF
>
> The only beads I know of that are suitable for HF are the tiny beads that
> W2DU found 30 years ago for his chokes. They only fit miniature coax, and
> it takes HUNDREDS of them to make a choke that still doesn't work as well
> as the multi-turn I've described. Those made with fewer beads are less
> effective AND they can be blown up with high power.
>
> 73, Jim Brown K9YC
>
>
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