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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