Dealing With Terrestrial 5G, Cellular, FM or Radar Interference

Terrestrial 5G, Cellular, FM or Radar Interference (C-Band and S-Band)

Objective: Protect satellite downlinks from strong nearby terrestrial RF systems using adjacent or overlapping spectrum.

Typical Symptoms

Degraded C/N on specific C-band downlinks, often:

• Worse at certain times of day (busy hours for 5G or radar)
• Localized to sites near cities, airports, ports, or broadcast towers

Spectrum analyzer shows:

• Strong carriers or wideband noise in bands like 3.3-3.8 GHz (5G), FM, or pulsed radar sitting adjacent to or within your receiver's front-end bandwidth

Immediate Actions (0-15 Min)

• Confirm the issue is local to one or a few sites (not fleet-wide)
• If possible, temporarily:
  • Rotate the antenna slightly to see if interference level changes (suggesting local source)
  • Insert any available bandpass filter ahead of the LNA or LNB

Investigation (15-120 Min)

Step 1: Characterize the interferer

Use a real-time spectrum analyzer (RTSA) to:

• Identify signature (OFDM 5G, pulsed radar, FM)
• Measure power levels versus your receiver's linear range and recommended max input (e.g., -60 dBm)

Step 2: Direction finding

Use RTSA plus mobile interference hunting tools to localize the source if multiple potential emitters are nearby.

Step 3: Site audit

Inspect:

• Filter installation (waveguide seals, flanges, gaskets) for RF leakage
• Nearby RF infrastructure (new cell towers, radars, microwave links, broadcast sites)

Mitigation and Recovery

• Install or optimize high-rejection bandpass filters at each affected site
• For severe cases:
  • Re-locate the antenna to a more shielded position
  • Adjust antenna height or azimuth to reduce line-of-sight to the interferer
• Coordinate with regulators or terrestrial operators:
  • Provide measurements and request power reductions or alternative configurations where rules support it

Prevention

• Include RF environment surveys in site selection and acceptance
• Keep a register of nearby spectrum licenses (5G, radar, broadcast) and track changes
• When new terrestrial services roll out, plan pre-emptive filter upgrades and spectrum clearing campaigns