[TowerTalk] VHF/UHF Common Mode Choke

jimlux jimlux at earthlink.net
Fri Jun 28 20:49:01 EDT 2019

On 6/28/19 3:32 PM, Jim Brown wrote:
> I recently did some work on chokes for 6M and posted the result to an 
> email reflector devoted to grid chasers for that band. Two turns of 
> RG8-size coax through a 1-in id. #31 clamp-on is optimum for 6M, and 
> yields about 1K ohms resistive choking Z. I recommend at least two such 
> chokes in series at the feedpoint. For RG8X or RG400, two turns through 
> TWO 3/4-in i.d. cores is optimum for 6M, and yields about 1.2K choking 
> Z. Again, use at least two such chokes in series.
> For 2M, use multiple #31 clamp-ons, sized to fit the coax. Use the link 
> below to select the size that fits your coax. Each will provide about 
> 250 ohms choking Z on 2M. Do not wind turns, just clamp them onto the 
> coax. I would use at least five, and ten is better. :)   Arrow is a good 
> vendor for parts they have in stock.

Is 31 a good material for UHF? I always think of it as a HF material, 
but it could well be useful up to 500 MHz.

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