Topband: Toroidal common mode choke

[ZR]

----- Original Message ----- 
From: "Jim Brown" <jim at audiosystemsgroup.com>
To: <topband at contesting.com>
Sent: Saturday, November 17, 2012 1:12 PM
Subject: Re: Topband: Toroidal common mode choke


> On 11/17/2012 9:12 AM, Bill Conwell (home) wrote:
>> I've seen articles that studied the optimum number of turns for air-core
>> chokes, but don't recall seeing any for toroidal chokes.  Can anyone 
>> offer a
>> pointer (or empirical data) that might guide me.  (20 turns?)
>
> See http://audiosystemsgroup.com/RFI-Ham.pdf   which includes both 
> measured data for many choke configurations and core materials, and 
> specific recommendations for winding transmitting chokes for the ham 
> bands. For 160M, Fair-Rite #31 material is the weapon of choice, and 16 
> turns of a pair of #12 enameled wire (connected a parallel wire 
> transmission line) makes a very effective choke for 160M and 80M, with Zo 
> on the order of 50 ohms. #12 THHN works as well on 160M and 80M, and has 
> bandwidth good to at least 20M, with Zo of about 100 ohms.  If that level 
> of mismatch concerns you,  remember that it's only a few feet of line, 
> less than 1/200 of a wavelength at 1.8 MHz.
>
> 73, Jim K9YC


The question was for RG-58. Have you made tests using that and published it?

Also the difference between Mix 31 and 43 is not great and was used for 
decades successfully before 31 was introduced.

Carl
KM1H