[RFI] Snap-on Ferrites

[Charles Coldwell]

Could this have something to do with the unavoidable gap in the
high-permeability material in a snap-on ferrite?  The majority of the
MMF is usually in the air gap.

On Mon, Jun 19, 2017 at 6:47 AM, N2TK, Tony <tony.kaz at verizon.net> wrote:
> Here in upstate NY I have Fair-Rite FT-240 #31 cores on my RG6 receive
> antennas - 8 turns. This spring when I did an inspection I saw that several
> cores had split or had chunks out of them. Do the cores need to be protected
> from the weather? I replaced the broken cores with the biggest clamp-on,
> #0431177081, #31 ferrite with 8 turns. They are just lying on the ground.
> Should I enclose them?
>
> I made up four 3/4 wave length RG6 lines for my 80M 4-square. I used the
> same biggest clamp-on ferrite with 8 turns at the feedpoint. Should I do
> anything additional such as tie wrap them and/or enclose the ferrite?
>
> 73,
> N2TK, Tony
>
> -----Original Message-----
> From: RFI [mailto:rfi-bounces at contesting.com] On Behalf Of Ed K0iL
> Sent: Sunday, June 18, 2017 11:20 PM
> To: john at kk9a.com; rfi at contesting.com
> Subject: Re: [RFI] Snap-on Ferrites
>
> John,
>
> Seems we can always get more turns around a toroid ferrite (several) than
> you can on a snap on ferrite (maybe one).  This would make snap-ons less
> effective than a toroid core based on number of turns.
>
> 73, de ed -K0iL
>
> -----Original Message-----
> From: RFI [mailto:rfi-bounces at contesting.com] On Behalf Of john at kk9a.com
> Sent: Sunday, June 18, 2017 9:44 PM
> To: towertalk at contesting.com; rfi at contesting.com
> Subject: [RFI] Snap-on Ferrites
>
> I was reading the recent QST article RF Mayhem by WB8IMY. The author said to
> avoid using snap-on ferrites for problems caused by HF signals as they
> rarely work well at HF. It is best to stick with circular cores.
>
> Is this correct?  I was not aware that snap-ons were less effective.
>
> John KK9A
>
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-- 
Charles M. Coldwell, W1CMC
Belmont, Massachusetts, New England
"Turn on, log in, tune out"