Hi Jim,
Yeah, one could probably automate all the calculations as you describe.
I think some of the design calculators described in the presentation
might be included with the 5th edition of ON4UN's Low-Band DXing book.
Unfortunately, I never got around to buying that edition and now it is
out of print. So far, I haven't been able to find a used copy.
73, Mike W4EF.............
On 1/22/2022 8:16 PM, Lux, Jim wrote:
On 1/22/22 6:53 PM, Michael Tope wrote:
Mike,
This presentation goes into excruciating detail on how to make all
the necessary design calculation to setup and optimize the Comtek
style hybrid in a 4 square array:
https://www.kkn.net/dayton2011/Demystifying%20the%20hybrid%20coupler-vers-FOR%20k3lr.pdf
The presentation focuses on an 80 meter design, but there should be
no reason you can't change the frequency to 28 MHz and re-run the
calculations to scale it for 10 meters. Without diving into the
details of the design, the extent to which stray reactance in the
layout and frequency dependent component limitations compromise
performance at 28 MHz is not clear to me. It sounds like a fun
experiment.
This is really useful..
And with cheap VNAs, dialing it in (if needed.. it's critical for
nulls, not so much for forward gain) would be easier.
What I've done for these things where you have frequency dependent
networks is run NEC from a python script that generates NEC input
files for each frequency. Then, another python script extracts the
numbers of interest from the output file(s).
In fact, you can run multiple different models in the same NEC run -
XQ card runs the model, then a bunch of new LD and NT, then XQ again.
As long as the *geometry* is the same, it's pretty fast (because the
hard part is computing all the couplings between the segments in the
physical antenna). A change in frequency changes the interaction matrix.
And it lends itself to parallelization on a cluster, if you have
access to one.
If someone wants copies of my codes, let me know, and I can send them
to you.
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