Hi Phil: One of the projects I worked on before retirement required a very
effective coax feedline choke. I solved the problem by stripping the lossy
vinyl off a short section of the feedline, winding it on a grooved lucite
rod to make an inductor, and connecting a variable capacitor across the
inductor. When this is tuned to resonance the impedance developed is
considerably higher than the usual self resonant coils we use and there is
no cut and try needed. If you want to do the absolute best job, I would
strip the vinyl and shield off the coax used in the inductor and insert it
into a close fitting piece of copper tubing. Coil this into an inductor and
I believe this would be an excellent solution to your problem. You would
probably want to mount this assembly in a weather proof box.
73, Dan, N5AR
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com]On Behalf Of Phil Clements
Sent: Wednesday, November 01, 2006 8:57 AM
To: towertalk@contesting.com
Subject: [TowerTalk] 2 Meter Antenna Mounted on a 160 Meter Vertical
I have a 160 meter ground plane antenna. It consists of 200 feet of Rohn 25,
with insulators at the 60 foot level. I want to put a 2 meter vertical
antenna (DB-224) atop the tower. Heliax will be run from the DB-224 down to
the 60 foot level on the tower.
I need ideas on how to decouple the 2 meter feed line across the insulators
so that 160 meter operation will not be affected. I presume some sort of
choke can be wound out of RG-8 cable on a PVC form. The question is the
construction of such a choke. How many turns on a 6 inch piece of PVC pipe
will be required, etc.? What other methods have been successfully employed
that you have heard of or tried?
Thanks in advance for all advice!
(((73)))
Phil Clements, K5PC
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