Wire length (electrical)
–
Counterpoise
–
Check with NEC-2
models this wire and counterpoise over real groundFor a half-wave, finds the length that resonates at your frequency; then works out the impedance through the unun on every HF band, and the take-off angle. Takes 10–20 seconds.
Elevation pattern
Along the wireAcross the wiredBi, rings every 5 dB
SWR on 50 Ω through the unun
Ideal unun, no losses
Every HF band
SWR is on 50 Ω after an ideal unun of the chosen ratio, at the best point in each band. Real ununs lose some power and are less exact, especially on the higher bands, and many have a small capacitor across the input to improve 10–20 m.
3D view
drag to turn, pinch or scroll to zoom, double-tap to resetLoading the 3D view…
To scale: the wire, counterpoise, pole and a 1.8 m person. Run the NEC model to add the radiation pattern.
Cut list
Cut the radiator slightly long and fold the end back to trim.
Trim to resonance
Measure through the unun where SWR is lowest, for example in the Sweep Analyser.
The far end of an end-fed half-wave carries a very high RF voltage, of the order of a kilovolt at 100 W. Keep it out of reach of the public and away from anything it could touch. Keep every wire clear of power lines.