[Elecraft] Balanced solution for KAT500 tuner?

[Bob K6UJ]

I have the same question.  The parallel wire feeder can pick up noise also by itself.

Bob
K6UJ



On Sep 29, 2012, at 11:10 AM, ab2tc wrote:

> Hi,
> 
> So are you suggesting using a choke balun on both ends of the parallel wire
> feedline?
> 
> AB2TC - Knut
> 
> 
> Jim Brown-10 wrote
>> On 9/29/2012 5:40 AM, Barry, Stephen wrote:
>>> Does Elecraft have a balun solution for balanced feeders for the KAT500
>>> at 500 watts?
>> 
>> See the Choke Cookbook that is Chapter 8 in my RFI Tutorial, and the 
>> discussion in the preceding pages, for an excellent common mode choke 
>> that will satisfy this need.  Use one of the chokes that is bifilar 
>> wound with #12 THHN, connected as a parallel wire transmission line 
>> between your parallel wire line and the tuner.
>> 
>> http://audiosystemsgroup.com/RFI-Ham.pdf
>> 
>> BTW -- the words "balanced feeders" and "balanced feedline" are pure 
>> fiction. You will note that I used the words "parallel wire" to describe 
>> the feedline.
>> 
>> The balance of any system, including an antenna system, is defined equal 
>> impedances to the reference plane. For antenna systems not on aircraft, 
>> that reference plane is the earth, and the transmission line is only 
>> part of that system. Most wire antennas that hams are able to erect are 
>> unbalanced by their surroundings, which in turn causes the feedline to 
>> be unbalanced. Imbalance in an antenna is caused by off-center feed, 
>> ground slope, sloping wires, trees, buildings, even the varying ground 
>> conductivity around the antenna.
>> 
>> This imbalance will cause current on the feedline to become unbalanced, 
>> which makes it part of the antenna. The feedline picks up noise and 
>> couples it to the antenna (because it's part of the antenna).
>> 
>> For this reason alone, smart hams have learned to use a common mode 
>> choke at the feedpoint of an antenna  This decouples the feedline from 
>> the antenna, preventing noise pickup (and keeping RF out of the shack).
>> 
>> 73, Jim K9YC
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> 
> 
> 
> 
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