You can then try inserting a choke at the feedpoint in the EZNEC model
and see how it does indeed change the SWR on the feedline!
The SWR is bound to change under those conditions. If you have a low CM
impedance back along the coax braid outer surface, which is shunting one
side of the antenna to ground, the impedance "seen" at the end of the
feedline is bound to change when you then use a choke to make that shunt
CM path a much higher impedance.
Steve G3TXQ
On 23/06/2014 05:03, Joe Subich, W4TV wrote:
In fact, get EZNEC or another modeling program that will show you the
currents in each segment. Then play with the length of that third
wire to see what happens to those currents at various lengths of
wire ... what happens to "feedline radiation" and how beam patterns
can become corrupted/skewed. It's quite interesting and educational.
73,
... Joe, W4TV
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|