What happens if the receiver antenna stays inside the panel?
A metal panel behaves like a Faraday cage and largely absorbs the radio signal. If the antenna stays inside the panel the range can drop to a level measured in metres, commands are received intermittently and the source of the fault is assumed to be the product. The solution is to bring the antenna outside the panel, in a vertical position and a few centimetres away from metal surfaces.
A sheet steel panel is an almost closed box as far as radio waves are concerned. The antenna inside communicates with the surroundings only through the weak signal leaking through cover gaps and cable holes. The result:
- The range falls far below the catalogue figure.
- The operator sometimes gets a response and sometimes does not; the fault looks intermittent and diagnosis becomes difficult.
- The operator starts working by moving closer to the panel with the remote control, which in turn undermines the discipline of working while watching the load.
Correct practice: bring the antenna outside the panel cover using a suitable gland or antenna mount. Fix it in a vertical position, keep it a few centimetres away from large sheet metal surfaces, and keep it away from the inverter and motor cables. Do not cut and shorten the antenna cable.
If your receiver is of the IP67 outdoor type the same rule applies: the situation is better if the housing is not metal, but if the receiver has been buried inside a sheet steel box or the machine chassis, shadowing will still occur. Always do the post-installation test from the furthest point of the site while the inverter and other loads are running; a test done in an empty panel gives a misleading result.
The full topic: 433 MHz or 2.4 GHz?