[TowerTalk] Another Cushcraft shorty-forty question

john at kk9a.com john at kk9a.com
Fri Aug 7 12:13:34 EDT 2015


I agree, the Cushcraft loading coils are pretty inefficient and it is
probably why the SWR bandwidth of their 40 shorty is so good.  OptiBeam,
JK and Force12 make very nice High-Q 40m coils.

John KK9A

To:	<towertalk at contesting.com>
Subject:	[TowerTalk] Another Cushcraft shorty-forty question
From:	"Jim Thomson" <jim.thom at telus.net>
Date:	Fri, 7 Aug 2015 07:06:30 -0700


Date: Thu, 06 Aug 2015 20:02:29 -0400
From: RMorris <robrk at nidhog.net>
To: George Dubovsky <n4ua.va at gmail.com>, kz8e at wt.net, towertalk
<towertalk at contesting.com>, Tim Jellison <kl7wv at kl7wv.com>
Subject: Re: [TowerTalk] Another Cushcraft shorty-forty question



##  another option is to toss the 68 turns of 12 ga magnet wire used to wind
the oem coils..and replace with
3/16 inch Al tubing coils.   8 ohms  vs .8 ohm.
http://www.qsl.net/ve6wz/CC_coil.html  If cu is used, it drops down to .5
ohm.

##  Ken at W3JK, uses  .25 inch solid AL for his 40m coils..then just uses AL
standoffs at each end of the coil...
similar to what F-12 used on there yagis.    The .25 inch al solid coils are
stuffed into the .25 inch hole at the end of the
al standoff....and protrude a bit out the other side.  Then just tig or
heliarc
wled em.   Solid connection, zero ohms.
3/16 solid AL could also be used.

##  I used .375 silver plated CU tubing to replace the LL rods on my F12 
340N.
  .07 ohm per coil.

##  IMO, the oem 12 ga magnet wire that CC used on solid fiberglass has
way too
much loss for the loading
application.

Jim   VE7RF



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