Topband: success with the inverted L

Jim Brown jim at audiosystemsgroup.com
Wed Dec 26 11:27:22 EST 2007


On Tue, 25 Dec 2007 13:40:44 -0600, FireBrick wrote:

>I built the 12 turns of rg58 through a FT240-61 core as suggested on the 
>K9AY site  
>Between the U and balun and my viking tuner, I have a good match.

FWIW, 12 turns of coax through an FT240-61 core is a LOUSY choke on 160 (in 
fact, it's a lousy choke on most bands). A MUCH better choke for 160 would 
use the #31 cores we bought in a group purchase several years ago. It won't 
affect the MATCH, but it will do a far better job of decoupling the antenna 
from the transmission line, which can make the antenna quieter on RX. 

See the section on coax chokes in  http://audiosystemsgroup.com/RFI-Ham.pdf

and http://audiosystemsgroup.com/CoaxChokes.pdf

73,

Jim Brown K9YC







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