Knowledge Base
What is cell signal booster oscillation? What causes oscillation? How can I fix the problem?
Oscillation is a feedback loop that occurs when the amplified signal from a cell signal booster’s inside broadcast antenna gets picked up by the outside donor antenna. This results in a continuous loop of amplified signals, similar to when a microphone gets too close to its speaker. This feedback loop prevents the booster from operating correctly.
In the event of signal oscillation, cellular boosters manufactured since 2014 have been required by U.S. federal regulations to automatically reduce their power or shut down entirely to prevent interference with nearby cell towers.1
Many boosters have one or more indicator lights that tell you oscillation is occurring. Some boosters have an LED or LCD display or a smartphone app that notifies you of the problem.
To fix the problem of oscillation in a cell signal booster, try the following steps:
- Reposition the antennas. Make sure that the internal and external antennas are placed as far apart as possible. Vertical separation is more effective than horizontal separation. For building booster systems, the ideal separation is typically around 20 feet (6 meters) or more; vehicle booster systems have lower gain and require less separation. This distance helps to minimize the feedback loop and reduce the chances of oscillation.
- Adjust antenna direction. If your booster system has directional antennas (outside and/or inside), make sure that the external antenna is pointed away from the internal antenna to minimize the possibility of signal feedback. Experiment with different angles and orientations until the light(s) or display on your booster tell you the problem has been resolved.
- Increase antenna isolation. Add physical barriers or shielding between the internal and external antennas. This can help to reduce the amount of signal overlap between the two antennas and prevent oscillation. You can use metallic sheets or other dense materials to create a barrier. In a vehicle, the metal roof should provide adequate isolation; glass, canvas, fiberglass, or other roofs will allow signal through and require greater antenna separation to compensate.
- Reduce booster gain. Some signal boosters allow you to adjust the output gain level with knobs, a touchscreen display, or a smartphone app. Lowering the booster’s gain will reduce the chances of oscillation. Refer to the user manual of your specific booster model for instructions on adjusting the gain.
- Install an attenuator. Some booster overload issues with building systems can be solved by inserting an attenuator between the booster and the outside antenna (or occasionally between the booster and the inside antenna). Consult your reseller or manufacturer for help determining if an attenuator is needed and will help you.
- Consult a professional. If you’ve tried the steps above and the oscillation issue persists, consult a professional installer or contact the manufacturer’s customer support for further assistance. If you purchased your booster from Powerful Signal, we offer lifetime support on your booster system, so please feel free to contact us—we’ll be happy to help you!
Notes
1 “47 C.F.R. § 20.21(e)(8)(ii)(A). “Anti-Oscillation. Consumer boosters must be able to detect and mitigate (i.e., by automatic gain reduction or shut down), any oscillations in uplink and downlink bands. Oscillation detection and mitigation must occur automatically within 0.3 seconds in the uplink band and within 1 second in the downlink band. In cases where oscillation is detected, the booster must continue mitigation for at least one minute before restarting. After five such restarts, the booster must not resume operation until manually reset.”
