Commercial examples of what I was trying to replicate, ...
https://www.balundesigns.com/qrp-model-1110-1-1-isolation-choke-balun-1-54-mhz/
https://www.hyendcompany.nl/antenna/portable_mini_hyendfed_antenne/product/detail/292/Portable_Line_Isolator_200_Watt__SSB
On Tue, Apr 5, 2022 at 4:36 PM David Hale <astronomerdave@gmail.com> wrote:
>
>
> 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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