Andrew, thanks for the flowers!
See my reply to Ron VK3AFW above. One finds quotes online such as the following:
- “for thicker wires the length of the antenna must be increased slightly”, and
- “an HF dipole will be SLIGHTLY shorter when built with insulated wire due to the dielectric effects of the insulation - a common figure is 3%”,
Trying to quantify these accurately in a program, unless it’s NEC, would be a mostly pointless exercise in frustration. You’re welcome to try this yourself, but for me, and for SOTA purposes, it’s a non-starter.
One factor which people often forget in building wire antennas is they often use a soft-copper (non-hard drawn) wire which they may have lying around in the workshop. After it’s been strung up a few times, the copper wire will be found to have stretched considerably, making a mockery of hyper-accurate antenna length calculations. So, hard-drawn copper wire or, better, copper-clad steel wire would be a better choice [Edit: for stability of length over time this may well be true. But see Richard G3CWI’s comment below on the poor handling characteristics of such wires.]
Anyway, just cut your wire sections a little longer than calculated, add a bit more for your connector(s), string the antenna up over “average ground ” and tune each part of the antenna in turn by cutting off small pieces until you’re happy with that section. Start from the center section and work outwards. It ain’t rocket science - I hope!