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Re: [TowerTalk] CMC-230-5K

To: <towertalk@contesting.com>
Subject: Re: [TowerTalk] CMC-230-5K
From: <john@kk9a.com>
Date: Tue, 19 Apr 2016 17:48:35 -0400
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
I was also thinking that it's easy to wrap the indoor coax though a ferrite
and eliminate the extra connectors and enclosure. 

If you have a good choke at the antenna and good coax, is there a reason for
having another choke inside the shack?

John KK9A

To:     towertalk@contesting.com
Subject:        Re: [TowerTalk] CMC-230-5K
From:   Jim Brown <jim@audiosystemsgroup.com>
Reply-to:       jim@audiosystemsgroup.com
Date:   Tue, 19 Apr 2016 10:06:02 -0700

There's something I don't understand here. In 2007, I published the research
upon which all of this is built, with measured data for a broad range of
chokes for the ham bands, and with full instructions for buying the cores at
very good prices, and a "cookbook" for the various ham bands. Why in hell
would you want to pay someone 3x the cost of doing it yourself, when all you
have to do to do it yourself is wind turns of coax through ferrite cores?

AND -- l would not trust any published power ratings for ANY chokes without
understanding the common mode voltage that they will see in any given
installation. To do that, you've got to put them in an NEC model that
approximates YOUR installation. Simply putting one of these chokes in a
sealed enclosure greatly reduces its power handling because it greatly
reduces air flow around the choke.

73, Jim K9YC

On Tue,4/19/2016 3:30 AM, Jim Thomson wrote:
I just received a pair of  CMC-230-5K  common mode chokes...from
MyAntennas.com 
to experiment with.
They are configured as a  line isolator, with  silver-teflon  SO-239s  on
each 
side.  They can also be configured as
a balun, with a pair of standoffs on the balanced ant side if you like.   
Extremely well designed and built, better
than I expected.

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