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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