Hi Bob, you are probably right about the different software standards. The
NEC-2 Users Manual, p8, first paragraph, states: "Delta/a must be 'about'
8 for errors 1%". I guess the developers of 4nec2 considered the error
for Delta/a 6 to be acceptable.

Yes, and now I am wondering where I got this value of 6 instead of 8...

However when delta/a (len/radius) 6 a warning is generated, when
delta/a 2 an error is generated. When using more thick wires, you can
add the EK card. With this more high delte/a values are possible.
(warning if delta/a 2, error if delta/a 0.5).

Greetings from the 'developer',

Arie.

p.s. I can also recommend www.cebik.com