Dimensions
Cebik's MoxGen equations (W4RNL), which depend on element diameter in wavelengths. C, the gap, is the critical dimension: hold it to within about 3 mm.
Check with NEC-2
models this Moxon at your height and groundGives the feed impedance, SWR bandwidth, forward gain, front-to-back ratio and take-off angle. Takes a few seconds.
Azimuth at take-off
dBi, rings every 5 dB
Elevation, front and back
Forward on the right, back on the left
SWR on 50 Ω
Modelled SWR
3D view
drag to turn, pinch or scroll to zoom, double-tap to resetLoading the 3D view…
To scale: the antenna, mast and a 1.8 m person. Run the NEC model to add the radiation pattern.
Build list
Driven element and reflector are separate wires. The gap C is open air (an insulating spacer or cord holds it). Add your own allowance for fixing loops.
Tuning tips
If the lowest SWR falls below your design frequency, the beam is electrically large: scale every dimension by fmeasured ÷ fdesign. Check the gap first: a gap that has closed up drops the resonance and ruins front-to-back.
Quick reference, UK bands
For the current element diameter. Click a row to design for that band.