Radiation Pattern
The radiation pattern is the map showing how an antenna's gain is distributed by direction, and it is given as horizontal and vertical plane cuts. The pattern of a vertical monopole is doughnut-shaped in the horizontal plane: it radiates equally in every direction but has a radiation null directly above and directly below it. That null creates a real dead zone in the field.
The pattern shows where the antenna's gain is spent. A single dBi number in the catalogue describes only the strongest direction; what you need to look at when making an installation decision is the pattern itself.
- Horizontal plane: almost circular for a vertical monopole; the operator walking around the receiver causes no problem.
- Vertical plane: there is a deep null in the top and bottom directions.
- With high gain antennas the beam narrows and the null regions widen.
In crane applications this comes up directly: when you mount the receiver antenna at a high point, an operator standing right underneath it may receive a weaker signal than expected. The solution is to shift the antenna a few metres to the side or to place it where nobody stands directly beneath it. Taking the receiver antenna to the highest point of the machine is usually right, but positioning it at the edge of the working area rather than right above its centre gives a more stable result.
Context where this term is used: Wireless remote control installation: pairing, relay, safety