On Tue, Apr 5, 2022 at 4:23 PM Jim Brown <jim@audiosystemsgroup.com> wrote:
> On 4/5/2022 4:10 PM, David Hale wrote:
> > I use K9YC-design CMCs (from the "Cookbook") all around the shack.
>
> The primary application for these chokes is at the feedpoint of antennas
> that are matched to their feedline at frequencies of interest; secondary
> application is down the line from the feedpoint of high dipoles as "egg
> insulators" to prevent them acting as parasitic elements of nearby
> vertical antennas. I don't know of any good reason to use them in the
> shack.
>
"in the shack" was loose, not literal. They are at the feedpoints of my
antennas. Also where the cable internet comes in to the house.
>
> As to your application, a so-called end-fed half wave (which is a half
> wave on only one frequency), these chokes can be applied at the
> feedpoint on frequencies where the SWR is fairly low, and/or the power
> is fairly low. They're likely to fry with high SWR and high power. I
> don't know of a practical choke for lines with high SWR at the point
> where they are inserted. In such a situation, if they don't fry with
> moderate power they aren't doing anything useful.
So if I have an EFHW, which has a 49:1 transformer, on the transceiver-side
of that transformer is low SWR. What I have now is a length of coax that
goes to the transceiver. Some people might suggest a counterpoise, others
might suggest a length of coax and let that be part of the antenna. I kind
of wanted that length of coax to not be part of the antenna. You are saying
that I shouldn't put a CMC there? When I've inserted a large one (made with
the aforementioned Fair-Rite 2631803802 and RG400 from the cookbook) at
the feed point of an EFT-10/20/40 I happen to have, I seem to get better
results but maybe I'm fooling myself.
73, Dave N3WTK
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