Quick Answer
Most booster interference comes from insufficient isolation between donor and service antennas, or from gain set too high. Keep the antennas separated, use ALC/AGC, and reduce gain if the system oscillates or the operator reports interference.
Why interference happens
A booster takes a weak outdoor signal, amplifies it and re-transmits it indoors. If the service antenna is too close to the donor antenna, the boosted signal feeds back into the donor, causing oscillation and out-of-band noise. High gain on a weak donor can also amplify noise and raise the noise floor for the operator.
Design rules that prevent it
- Keep horizontal and vertical separation between donor and service antennas; use walls and building structure where possible.
- Use ALC/AGC and set gain below the oscillation threshold, not at maximum.
- Aim the donor at the serving cell and avoid pointing it at another operator’s antenna.
- Confirm local type approval and operator requirements before installation.
If interference is suspected
Turn the system off, check antenna isolation and cable/connector quality, then restart at minimum gain and increase slowly. If the operator reports interference, stop transmitting and coordinate with the operator before further testing. Do not keep increasing gain to chase coverage.
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Frequently Asked Questions
How much antenna separation is enough?
It depends on host gain and antenna type. Use the manufacturer’s minimum separation as a starting point, add building structure between antennas, and confirm with a gain/oscillation test at commissioning.
Can ALC/AGC prevent all interference?
No. ALC/AGC helps control output, but physical isolation and correct gain settings are still required. A poorly isolated installation can oscillate even with ALC/AGC.
What should I do if the operator complains?
Switch off the booster, document the installation, and contact the operator. Do not restart at high gain until the cause is identified and the installation is corrected.