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.
Magenta —
waves from antenna 1, the lower dot, always fed as the phase reference (0°).
Cyan — waves
from antenna 2, the upper dot, fed with the selected lagging phase relative
to antenna 1.
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.
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.