[TowerTalk] XM240 element spacing

[Leeson]

The story on modeling the Moxon Yagi is that I got lucky. Because I had 
been working with Brian, K6STI, I designed this antenna in 2003 using 
AO, and built it to the dimensions it produced. No offset factors were 
used. It's been up since 2003, and is about the biggest antenna we can 
keep in the air here on a 3400' high ridge facing the Pacific (147 mi/h 
max 3-sec gust measured).

AO uses MININEC, which uniquely handles the right angle stuff that NEC2 
does not. Apparently NEC4 works OK, but I haven't tried it myself. So 
while it's true that the NEC2 analyses show the SWR is off in frequency, 
it turns out the physical reality is as hoped for.

When I was a grad student, I was most impressed when a prof made the 
point, "the model is not the thing," probably the single best lesson 
from all my years there. I tell my students, "Experiment trumps theory." 
A quote about this from K3LR is something like, "just build them to the 
dimensions, they work."

An updated paper "40m Moxon 2018 Update, Greg Ordy, W8WWV,
June 13th, 2018" that tells us, "For antennas like the Moxon, that 
cannot use the stepped diameter correction algorithm, NEC-4 (or MININEC) 
should be used as the modeling engine." I must have received this paper 
directly from Greg, as I don't find it online.

73 de Dave, W6NL/HC8L