Full Antenna Modeler

Design a wire antenna and see exactly how it will perform before you climb a ladder. Pick an antenna and a band, set the height and length, and this page runs a real antenna-modeling engine right in your browser. It breaks the wire into dozens of tiny segments, works out the current flowing in every one, and from that calculates the feed-point impedance, the SWR across the whole band and the radiation pattern in 3D. It is the same method of moments that professional programs like NEC2 and EZNEC use.

Tips

Height matters most. A dipole only a few feet up sends its signal straight up, which is great for NVIS on 80 m and 40 m (see the NVIS Advisor) but poor for DX. At half a wavelength up, the main lobe drops to about 30 degrees, ideal for working Europe. Try changing the height and watch the elevation pattern change. Inverted-V: a wider angle between the legs acts more like a flat dipole; a narrow angle lowers the impedance and shortens the wire needed. EFHW: the feed point is very high impedance, about 2,000 to 3,000 ohms, so it is shown through the usual 49:1 transformer, with a short counterpoise (about 5% of a wavelength) like the coax shield in a real installation. Vertical: the impedance shown assumes a good radial system or perfect ground; with only a few radials expect higher SWR and lower gain.

About the model: the engine uses thin-wire method-of-moments math (triangle current functions on short segments, solved with complex matrix math) that runs in your browser. It has been checked against textbook results: a half-wave dipole shows about 2.15 dBi of gain and a quarter-wave vertical over perfect ground about 36 ohms. Impedance with a real ground is figured over perfect ground, and the patterns use real-ground reflection for average soil. Wire loss, coax, nearby trees, gutters and towers are not included, so treat results as a very good starting point, then fine-tune with an antenna analyzer. Compare antenna types side by side on the Antenna Pattern Visualizer.