[TowerTalk] Hairpin Match Calculator

[Brian Beezley]

"NEC does use a simplified model for the "wire" - it takes into account 
dielectrics and skin effect (I'm in the middle of figuring out what ZINT 
does, which is the core of the "resistance and inductance of a segment", 
so I can make a Python version that's not just a copy of the Fortran)."


Jim, carefully check the NEC resistance calculations. Many years ago a 
knowledgeable German ham found an error and brought it to the attention 
of some NEC person. He was never happy with the acknowledgment he 
received. I assume the correction made its way into the code, but I 
never checked.

I found a free FEM program (code free, help costs) but it looks like a 
big effort to get it going. Not sure it's worth the trouble just for the 
boom problem.

A benefit of writing the hairpin code is that I'm now aware of subtle 
magnetic interactions everywhere. Some not so subtle.

For the hairpin Q calculation, I had been meaning to check loop 
radiation resistance. I finally got around to it yesterday. Radiation 
loss is below 1% of conductor loss for most designs, but I did find a 
few cases where it was 5-10%, and one case where it was 13% for a 
2-meter hairpin. More significant than I expected. So I added the code 
and posted a new version. I did the same thing to my coil program for a 
better comparison of coil and hairpin losses. I always wondered whether 
a large, efficient coil that replaced a hairpin might radiate, but so 
far I haven't found a case where the loss is anything but tiny.

Brian