Topband: Chokes, et. al. - what is the attenuation ?

[donovanf at starpower.net]

Hi Rick,

A monoband current forcing balun doesn't require as much coax as you might think.  The 1/4 wavelength of coax would probably be needed anyway, so the only "extra" length is the 3/4 wavelength coax and thats only 35 feet of RG-213 on 20 meters.  

http://www.qsl.net/i0jx/balun.pdf

For the price of 35 feet of coax you're 100% certain that the antenna feed is balanced.  Admittedly this doesn't scale very well to 80 and 160 meters, but its a great performer on the higher bands including 6 meters.

73
Frank
W3LPL

---- Original message ----
>Date: Sat, 14 Jul 2012 15:15:47 -0700
>From: "Richard (Rick) Karlquist" <richard at karlquist.com>  
>Subject: Re: Topband: Chokes, et. al. - what is the attenuation ?  
>To: donovanf at starpower.net
>Cc: topband at contesting.com
>
>
>
>On 7/14/2012 1:19 PM, donovanf at starpower.net wrote:
>> I'm liking my current forcing, 1/4 wavelength and 3/4 wavelength coaxial baluns more and more!
>>
>> 73
>> Frank
>> W3LPL
>>
>>
>
>On low bands, the Q of resonant stubs is fairly low.
>Therefore, the effective common mode impedance of these
>baluns will not be extremely high.  If you want a
>single band choke, you could get a higher impedance
>more easily by using a low loss ferrite like 61 or 67
>to make a conventional common mode choke and then
>resonate the choke with a shunt capacitor.  It also
>requires a heck of a lot less coax than a wavelength.
>
>Rick N6RK