Thank you 300ohm. I appreciate it. That's gives me something to look at.
FWIW: 4nec2 gave me some errors (radius messages, etc.) when I downloaed and ran the GH6 nec file, and for some reason the results in the pattern window were different than I was used to (arrows stepped across angles instead of frequencies).
I created a GH6 geometry from scratch (using a spreadsheet) and managed to get it to behave. Anyway, that's how I got here. I didn't download the GH10 file; I'll do that too (in addition to the EX suggestion).