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Topband: tuning elevated radials

To: <ford@cmgate.com>, <topband@contesting.com>
Subject: Topband: tuning elevated radials
From: "Jim Jarvis" <jimjarvis@comcast.net>
Reply-to: jimjarvis@ieee.org
Date: Fri, 16 Sep 2005 12:55:38 -0400
List-post: <mailto:topband@contesting.com>
Ford,

Questions and comments.

Q:  I like the rf probe idea...and I think I can draw the circuit
you created...but rather than speculate, can you either send me
something directly...or post here if easier... showing the 9 turn
windings and how you oriented and connected them to the bridge?

I'm assuming the coils are in series, and connected across 2 terminals,
with the meter across the opposing pair, bypassed with the cap.
The coils need to be wound in the same direction, correct?  What
ferrite did you use?

Comments:

1) I'm a fan of elevated GP's, whether folded in an ell or not.
I have tended to use 3 radials @ 120' spacing as well.  W1CX
convinced me that having 4 radials...two opposing pairs...would
produce a cleaner pattern, and less high-angle radiation. FWIW.

2)I can only speculate that your north radial is over earth which
is different from the other two, and that's the source of the imbalance.

3) As a practical matter, I have made several monobanders for 160, 80 and
40,
and one 160-80 dualbander, most with 3 radials per band.  In all cases,
I cut the vertical portion for the low end of the band, and cut radials
at 105%.  Then, I fold back the radials equally to bring vswr to target.
I just wrap them around themselves 2 to 3', and usually don't cut them.

This doesn't assure a balanced pattern, by any means, and I may explore
your approach at my new site, this winter.  Available trees lend themselves
to GP's.

Tnx.

N2EA
jimjarvis@ieee.org


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