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[TowerTalk] 80M loading coil - open coil or toroid?

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Subject: [TowerTalk] 80M loading coil - open coil or toroid?
From: "N2TK, Tony" <tony.kaz@verizon.net>
Date: Tue, 01 Jan 2013 15:43:01 -0500
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
For my 80M 4-sq with a Comtek box I use a 3.6 uh coil to resonate the
shortened (41') radials (minimum power in a dummy load at 3.76MHZ. In
addition I add a 4.1uh coil to resonate the radials at 3.53. Presently the
coils are 2" OD open coils made with tinned #14 wire.

Is there a reason I should use something like a toroid coils instead of
open coils, other than the weather making the coil forms brittle after
several years?

 

I found some cores in my junk box but not sure if they would work. They are
T-200, light blue. If I put a layer of glass tape and wind 6 turns of #12 on
the core utilizing the entire core I get 3.6uh. If I squeeze the turns
together so they only occupy half the core I get 4.1uh.  The problem is I
have no idea if these would be appropriate for full power on 80M. I don't
know if the color and/or inductance gives a clue as to what these cores are.

 

Any suggestions about using these cores or perhaps a better core for this
application or just buying or winding some open coils for this application?

All suggestions and input appreciated.

 

73 & HNY

N2TK, Tony

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