This shows the azimuthal radiation pattern of two vertical antennas fed with a controllable phase difference — a classic phased array. You're looking straight down from above, so this is the pattern as it spreads out over the ground in every compass direction. The two central dots represent the antennas, always arranged one above the other on screen along the array's axis.
Each antenna's waves are drawn in the color you choose for it in the controls below — antenna 1 (the lower dot, always the phase reference at 0°) and antenna 2 (the upper dot, fed with the selected lagging phase). Magenta and cyan are the defaults, with orange, sky blue, and yellow also available — the orange/sky-blue pairing in particular is chosen to remain clearly distinguishable for colorblind viewers, where magenta/cyan can be harder to tell apart.
A solid ring is a wave crest; a dashed ring is a trough. Both are equally strong when reinforcing — the solid/dashed distinction only marks which part of the wave's cycle you're seeing, not signal strength.
Brighter regions of the rings are lobes — directions of stronger combined signal. Dimmer, darker regions are nulls — directions where the two antennas' signals largely cancel. This is the main thing to read: trace the brightness around the full circle to see the antenna's actual directional pattern.
Since brightness fades gradually, it can be hard to pin down an exact pattern shape at a glance. The white outline solves that: it's a single continuous curve where the distance from center is directly proportional to signal strength in that direction, scaled so the strongest lobe reaches the outer edge. This is the same style used in classic printed antenna-pattern charts, and it updates only when you change spacing or phase — it won't animate along with the waves underneath it. Toggle it off any time you want an unobstructed view of the wave interference itself.
These mark the exact directions where the two signals arrive perfectly in phase — the true peaks of the strongest lobes. Depending on spacing and phase, an array can have one, two, or more of these directions simultaneously.
The gain value estimates how much stronger the signal is, in the strongest lobe direction, compared to a single non-phased vertical antenna fed with the same total transmitter power. These are idealized gain values, and actual gain values will vary somewhat with specific array conditions and environments.
Antenna separation sets the physical spacing between the two antennas, in wavelengths. Phase sets how far antenna 2's feed lags behind antenna 1's. Together, these two settings alone produce 40 distinct patterns — try stepping through them to see how dramatically spacing and phasing reshape the array's directionality, from simple bidirectional figure-eights to tight unidirectional cardioids to multi-lobed patterns at wider spacing. The two color dropdowns let you reassign each antenna's wave color independently, useful both for accessibility and for personal preference.