[TowerTalk] CMC-230-5K

[Jim Brown]

Hi Bob,

It can't hurt, but it's also unlikely to help unless your grounding and 
bonding is poor.

It IS a good thing to add a second choke on feedlines for wires that are 
long enough to interact with verticals in your antenna farm, and also to 
reduce the common mode voltage, and thus the power-related stress, on 
the choke at the feedpoint.

73, Jim K9YC

On Tue,4/19/2016 12:27 PM, Bob K6UJ wrote:
> 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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