[TowerTalk] OptiBeam OB2-40M

[Lux, Jim]

On 5/23/21 1:31 PM, Mike Zak wrote:
> Is there a paper, article, YouTube video, Powerpoint deck, chapter in a book, website, message-in-a-bottle, or anything else, that clearly and succinctly describes the trade-offs and interactions between yagi gain, pattern, and match?
>
> A 15 minute session with EZNEC, and a candidate yagi design, is plenty adequate for showing that there’s some serious systems engineering involved in coming up with the right set of trade-offs, starting with “which problem are we trying to solve?”  But few of us are ever going to capture the ideal design and then fabricate it.  So maybe if there was some insight around these tradeoffs we could all do a better job with our selections of commercially available products.
>
> Did W4RNL ever do anything along these lines? Or W2PV?  How about the Telrex archives?  Anyone have any suggestions for something that is readable by mere mortals?
>
> Mike, W1MU
>
>
I don't think so. I think it's what you say, using a modeling code and 
iterating to see what happens.

Kraus talks about how Yagi-Uda's work, but not much about optimization.

Orfanidis's book has examples, and matlab code to do a quick modeling 
that does the interelement coupling, then computing the pattern - that's 
where I started, because I'm fairly facile in Matlab.

Lately, I've been running models using Python and NEC 4.2 to try and 
come up with a "grass roots" understanding of trapped multiband antennas 
(using the ARRL antenna book example, with 32 feet inside trap, 22 ft 
outside trap (on one side) and 8.2 uH and 60 pF for the trap).

Do you want the trap resonance "in band" or "out of band".  In band 
gives better pattern performance (and potentially better efficiency), 
but is less tolerant of changes in frequency or trap component tolerance.

Similar questions about "tuning components in middle of element" - an 
inexpensive RCS-8V would potentially give you 32 capacitor values in the 
middle of an element.