[Amps] Triband balun

donroden at hiwaay.net donroden at hiwaay.net
Tue Mar 18 15:58:55 EDT 2014


REACTANCE

Don W4DNR




Quoting Jim Brown <jim at audiosystemsgroup.com>:

> On 3/18/2014 8:49 AM, Gary Smith wrote:
>> I'm going to try the 10 rolls of coax again, this time alone.
>
> Contrary to popular mythology, a coil of coax is NOT an effective  
> common mode choke, because it is inductive. An effective common mode  
> choke must have a large value of resistance at the frequency of  
> interest. Only a multiple turns wound through suitable ferrite cores  
> to form a low Q parallel resonant circuit are effective, and a LARGE  
> value of parallel resistance is needed both for power handling and  
> for noise suppression.
>
> See the "Cookbook" in k9yc.com/RFI-Ham.pdf for specific bands and  
> combinations of bands. 4-5 turns of RG-213-size coax through 5 #31  
> or #43 Fair-Rite cores covers 20-10M effectively.
>
> 73, Jim K9YC
>
>
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