Receiver Blocking (Desensitization)
Receiver blocking is when a strong nearby transmitter saturates the receiver front end and reduces its sensitivity. The interfering emission does not have to be in your band; a handheld radio or a nearby base station can push the front-end amplifier into its non-linear region even on a different frequency.
The low-noise amplifier at the receiver input works linearly up to a certain input level. When a very strong signal arrives it leaves that region; gain drops, unwanted mixing products appear and the weak wanted signal can no longer be decoded.
- Symptom: range is normally sufficient, but when a particular device runs the link drops even at short distance.
- Distance: because received power falls off quickly with distance, moving the antenna a few metres away from the interfering source is often enough.
- Filter: a band-pass front-end filter reduces the effect of out-of-band sources.
- Usage rule: not standing close to the remote control antenna while talking on a handheld radio is a simple and effective precaution.
This phenomenon differs from a rising noise floor: here the problem is not average noise but a single strong source saturating the receiver. For diagnosis, switching off the interfering source and retrying the link is the fastest method.
Context in which this term is used: Wireless remote control installation: pairing, relay, safety