An AM directional antenna gets its shape from several towers radiating together: change each tower's field ratio, phase, spacing, and bearing, and the horizontal pattern reshapes. Pick a tower count, load a preset, or set your own values and watch the radiation pattern and the aerial tower layout update side by side.
| Tower | Field ratio | Phase (°) | Spacing (°) | Bearing (°) |
|---|
Tower 1 is the reference (spacing 0° at the origin). Spacing is electrical degrees from the reference (90° = a quarter wavelength). Bearing is the compass direction from the reference to that tower (0° = North/up, increasing clockwise). Phase is the tower's electrical phase relative to the reference.
Both views are drawn with North up, like a map. The pattern is normalized so its maximum touches the outer ring. The aerial view plots each tower at its spacing-and-bearing position relative to the reference, measured in electrical degrees (90° = a quarter wavelength) and auto-scaled to fit; dot size reflects relative field ratio, and the reference tower is the open circle at the center.
Horizontal-plane array factor: the field in any azimuth is the vector sum over all towers of (field ratio) × e j(phase + spacing·cos(azimuth − bearing)). This is the standard method used in AM directional design. A noncommercial hobby reference compiled by N6JET, developed in collaboration with Anthropic's Claude.