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Re: [TowerTalk] CMC-230-5K

To: towertalk@contesting.com
Subject: Re: [TowerTalk] CMC-230-5K
From: Bob K6UJ <k6uj@pacbell.net>
Date: Tue, 19 Apr 2016 12:27:23 -0700
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Jim,

I am using your choke design on both of my beams. With all this discussion on chokes it got me to thinking. My tower is only 10 feet away from the back of the house. I'm not sure how much noise I have from the house so I am going to try adding an additional choke on the lower end of the coax going in to the shack. I hope I am pleasantly surprised and get a lower noise level.

Bob
K6UJ



On 4/19/16 10:06 AM, Jim Brown wrote:
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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