[TowerTalk] Grey PVC Loading Coil

[Keith Dutson]

Why not make the coil from small aluminum tubing without leaving the form in
place?  It would be easy to adjust.

73, Keith NM5G

-----Original Message-----
From: towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com] On Behalf Of Dan Zimmerman N3OX
Sent: Monday, December 04, 2006 10:42 AM
To: towertalk at contesting.com
Subject: [TowerTalk] Grey PVC Loading Coil

In the spirit of "some antenna is better than no antenna at all," I'm going
to add a base loading coil to for 160m to my 40 foot vertical
(http://www.n3ox.net/projects/lowbandvert).

I know it's a substantial compromise over other forms of loading, but I'm
willing to accept the efficiency penalty for convenience in this particular
case.  What I want to know about is whether or not grey PVC electrical
conduit is suitable for coil forms at 1.8MHz.  I searched the archives and
found a discussion on PVC formers for HF and that they're not unacceptable
unless you're running many close-spaced turns, but I wonder if people have
tried grey vs. white and what they've found.  I know the microwave trick is
routinely used but I don't think absorption at 2.4GHz says much about the MF
properties of the material.

I've got access to some 5" conduit and a lathe; a few minutes and I can have
a beautiful coil form like the 80m one on the page above, but I wonder if
the grey PVC is lossier than the white stuff?

There are plenty of other approaches, but if grey PVC is decent at 1.8MHz,
I'm just going to cut a nice  groove in it and go.  It's going to be
something like 20-30 turns of #10 wire and having a grooved form makes for a
quick and solid coil.

73,
Dan
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