Faraday Cage Effect
The phenomenon whereby a closed conductive enclosure isolates the electromagnetic field inside it from the outside environment. A metal electrical enclosure behaves exactly like this; if you leave the antenna inside the enclosure the radio signal is largely shielded and the working distance falls far below the open-field figure in the catalogue.
An electromagnetic wave striking a conductive surface induces a current in that surface, and the opposing field produced by that current largely prevents the wave from passing into the enclosure. Even if the enclosure is not fully closed, the shielding effect persists as long as the openings are small relative to the wavelength.
What this looks like in the field:
- Metal enclosure: if the antenna stays inside, range drops severely. This is the most frequently encountered installation error.
- Steel structures and reinforced concrete: the reinforcement behaves like a grid, causing noticeable loss for transitions between floors and behind walls.
- Containers and metal cabins: if the operator is inside a metal cabin, the same effect occurs on the transmitter side too.
The solution is simple: bring the antenna outside the enclosure, position it vertically and keep it a few centimetres away from large metal surfaces. If you are using an in-enclosure receiver (for example the LF100R), this step is not optional but a mandatory part of the installation.
When diagnosing a range problem, temporarily moving the antenna outside the enclosure and measuring the difference quickly distinguishes whether the problem stems from shielding or from interference.
Context in which this term is used: Wireless Crane Remote Control Selection Guide