[Amps] construct ferrite "line isolator"

[Jeff Blaine]

The mix is THE issue.  The permeability of the type 6 powder is microscopic by comparison to type 31 at low HF.  Get some type 31 
material and it will swat those RFI flys like they were nothing.

The next mistake guys make is not using big enough ones.  Larger sized units allow for multiple turns and so you get that 
exponential effect with each singular added turn.

The Fair-rite numbers for the type 31 mix are:

Solid core:        2631102002        this one is great for cables you make up in the shack.

Medium clamp on    0431164181

Large clamp on    0431176451

Huge clamp on    0431177081

There is a 2.4" x 0.5" round one that I use for the transmitting chokes and these are directly from Jim's article on the subject.

73, Jeff ACØC
www.ac0c.com
-----Original Message----- 
From: Bill, W6WRT
Sent: Tuesday, October 26, 2010 1:06 PM
To: amps at contesting.com
Subject: Re: [Amps] construct ferrite "line isolator"

ORIGINAL MESSAGE:

On Tue, 26 Oct 2010 11:44:03 -0400, "Carl" <km1h at jeremy.mv.com> wrote:

>
>Powdered iron is fine for tuned circuits and high power HF baluns where low
>loss is needed. Even Sevik woke up to that fact.

REPLY:

I know every situation is different, but over the years I have used
literally dozens of those "snap-on" ferrites with almost no success at
all. I have tried both the two-piece rectangular and the clamshell type
but I don't know what mix they are. Perhaps a different mix would be
better.

On the other hand a single moderately large powdered iron toroid has
always worked without fail.  I use Palomar's mix #6 (yellow) in about a
two inch diameter and wind as many turns through it as will fit,
typically about 10-12 turns for smaller wires. Excellent results.

Please note thatI am talking about RFI problems in the shack, not high
power baluns for the transmit coax.

73, Bill W6WRT
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