Personally I have never choked the 4 feedlines to the verticals. I fail to
see why the shield of the feedlines is different from the radials it is
connect to at the base of the vertical. On my raised 80m 4-square I have 7
radials from each base, starting with the one going to the adjacent vertical
they go outwards every 45 degrees using heavy aluminum wire, then the 8th
one to complete the pattern is the shield of the coax going to the comtek
box.
David Robbins K1TTT
e-mail: mailto:k1ttt@arrl.net
web: http://wiki.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://k1ttt.net:7373
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Jim
Brown
Sent: Saturday, September 24, 2016 16:30
To: towertalk@contesting.com
Subject: Re: [TowerTalk] 4 square for 80
On Sat,9/24/2016 7:15 AM, Steve London wrote:
> How much better would the performance be with a multiturn choke ? Over
> real ground, in the presence of real, possibly interacting structures
> within N wavelengths, isn't there a finite limit to the performance,
> regardless of your choice of "excellent" vs. "superb" common-mode
> chokes ?
Hi Steve,
The primary reason for using common mode chokes in our antenna systems is to
reduce RX noise. A string of beads choke is NOT a good choke at HF for the
reason cited -- it's effectiveness is strongly dependent on the electrical
length of the feedline considering it as an antenna (that is, considering it
as a wire, not a transmission line). This is not a matter of "excellent" vs
"superb," it is whether it is effective at suppressing RX noise, and whether
signal pickup on the coax fills in the nulls a bit.
73, Jim K9YC
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