[TowerTalk] How to mod a 40m 4-square for 10m use?

[Michael Tope]

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.