[Top] [All Lists]

Re: [TowerTalk] Shunt Feed Woes

Subject: Re: [TowerTalk] Shunt Feed Woes
From: Gary Johnson <>
Date: Sun, 8 Dec 2019 17:36:08 -0800
List-post: <>
I’m using a half-sloper for 80, not shunt feeding, but many of the effects and 
requirements are the same. On a 30 ft tower, I have a JK Navassa 5 and an 
OB1-4030. All coax is bonded at the top and bottom of the tower. Very careful 
and detailed simulation showed that common-mode choke dissipation on both 
antennas could be extremely high (>100 W, worst-case). My solution was to add a 
DPDT grounding relay at the feedpoint of each antenna that is activated only on 
80m. This guarantees that all those isolated elements are shorted to the boom, 
which increases the capacitive loading of the tower. That made the match much 
better on the half-sloper. We’re looking at adding another half-sloper for 160m 
and it will take advantage of those relays as well. Works great.

-Gary NA6O

TowerTalk mailing list
<Prev in Thread] Current Thread [Next in Thread>