AF4OZ conditional antenna calculations, 28 October 2026
201 NEC2C installation/sensitivity runs plus a free-space dipole benchmark.
These are hypothetical bare-wire scenarios, not calibrated models of installed products.
Start with the modeling section of the accompanying Word report (after page 13).
Baseline: Z_30_92 and E_130_180_short; average soil; maximum segment length 0.25 m.
Z tags: end height in feet; total assumed wire length in feet.
E tags: total main wire feet; tail azimuth degrees in model coordinates; return surrogate short or down.
E suffix t25/t45 changes tail length; h90/h110 changes apex height. Default apex 100 ft and tail 35 ft.
short = 2 m horizontal return; down = elevated wire ending 0.15 m above soil, NOT a buried rod model.
All patterns are normalized to accepted wire-source power. No actual transformer/tuner/line attached to NEC models.
Model .npz gain array axes: theta 0..90 degrees by 2; phi 0..360 degrees by 5.
Summaries and line calculations are in results.csv/results.json and matching_section.json.
Raw .nec inputs and .out solver output allow independent audit. No guessed current distribution was imposed.
Source repo https://github.com/KJ7LNW/nec2c at commit 55be1e0e3fe5ee9dad4ce6050711450d19c562fd.
Included solver source is GPL-3.0; see solver-source/COPYING. Source was compiled using clang -O2 and -lm,
with PACKAGE_STRING defined as a build label. The source was not otherwise modified.
Run run_models.py with Python and numpy after compiling solver to ../nec2c/nec2c, or adjust EXE.
Plot script additionally needs matplotlib. Input names must be short; run solver with model folder as cwd.
The runner retains existing raw outputs. Delete a scenario output before changing its input to recalculate.
No compass bearing for the EFHW is known; NW-SE is assumed to describe ZS6BKW span only.
No total installed-system efficiency, receive SNR, or communication reliability is established.

Product confirmation: EFHW-7510-2K-Plus as identified by the user, without pole-mount brackets.
The manufacturer stated 0.5 dB transformer loss was not used to calibrate the wire-model gain.
NI4L line transformation uses 40 ft, 420 ohm, VP 0.917; baseline wire length 92 ft is an assumption.
