[TowerTalk] CMC-230-5K

[jimlux]

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?

Time's not necessarily free?   For example, you can buy a spool of AWG 
12 house wire and improvise all manner of insulators to make a dipole, 
but sometimes it's nice to have all the stuff in a bag so you can hand 
it to someone and say "put it up in the air", no soldering, no other stuff.

We're often in a situation at work where we are short of people 
resources and have money, so buying something that's already assembled 
is expedient and "gets the job done".

So then, your incredibly useful report becomes something with which to 
evaluate the design of a purchased widget.





>
> 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.

Power ratings for amateur radio products are pretty non-standardized and 
speculative in general.





>
> 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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