[TowerTalk] RF Choke or Balun

[Jim Brown]

On Fri, 8 Jun 2007 09:28:49 -0400, Rick Ellison wrote:

>If I do make an RF Choke how many turns of rg8x will I need?

For use on 20-10 meters, wind four turns of the coax through a 
stack of 7 FT-240 cores made of #31 or #43 material. It is VERY 
important that you spread the turns as widely as possible to 
minimize the stray capacitance. If you don't, the choke will 
resonate around 3MHz, and be useless above 75 meters. Make the 
diameter of the windings as small as you can without deforming the 
center conductor of the coax. This choke will provide an 
essentially resistive impedance  greater than 4K ohms from 20-10 
meters. 

73,

Jim Brown K9YC