Interference Complaint From a Neighbor's Television
A neighbor two houses away reports that your 2 m FM transmissions break into their TV audio. You operate a 50 W mobile rig through a ground-plane antenna at 25 ft, and the neighbor's TV antenna is a rooftop Yagi aimed away from you. The interference occurs only when you transmit on the local repeater's input frequency (146.2 MHz). Your station is properly grounded, and you hold a General class license. The neighbor is polite but wants it fixed immediately. You have not yet confirmed whether the TV is connected to cable, satellite, or an antenna.
1. What is the correct operator response under the FCC's rules regarding interference?
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Under 47 CFR 97.101(d) and 97.103, an amateur must not cause harmful interference and must cooperate to resolve it. The Commission's rules do not require the amateur to stop operating if the station is compliant, but you must take reasonable steps to resolve the interference and respond to the complaint.
Key points:
- You are not automatically at fault; TV receivers must meet FCC Part 15 immunity standards.
- You should not modify the neighbor's equipment without permission.
- Document your station (power, antenna, frequencies) and the complaint.
- Offer practical remedies such as ferrite chokes on the TV's cables and a high-pass filter at the TV input.
- If unresolved, the FCC can be asked to assist, but the amateur should demonstrate good-faith effort first.
2. Outline a step-by-step diagnostic plan to identify whether the problem is fundamental overload, harmonic radiation, or cable ingress.
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- Determine the TV's signal source: cable, satellite, or antenna. If cable/satellite, the problem is almost certainly ingress into the cable or TV (common-mode pickup), not harmonic radiation.
- Check for harmonics: 146.2 MHz has no low-order harmonic in the TV bands, so harmonic radiation is unlikely; verify with a receiver or spectrum check if available.
- Test at reduced power: if interference disappears at 5-10 W, it is fundamental overload of the TV front end.
- Add a high-pass filter at the TV antenna/cable input and ferrite chokes on the coax and power cords; if the problem clears, it was ingress/overload.
- Check the TV antenna: a corroded or poorly grounded antenna system increases susceptibility.
- Compare with a portable radio near the TV to isolate whether the TV itself is the weak link.
3. The neighbor agrees to try filters. Which remedies do you supply, and how do you verify success without overstepping?
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Supply a high-pass filter (cutoff around 50 MHz) for the TV antenna input and snap-on ferrite beads for the TV's coax, power cord, and speaker leads. These are passive, non-invasive, and do not modify the TV's internal circuitry.
Verification:
- Test at your normal power on the repeater input while the neighbor watches the TV.
- Confirm before and after with the same channel and program.
- Do not enter the neighbor's home uninvited; let them install or ask permission to assist.
- Keep a log of the remedies and results in case the FCC or an ARRL interference specialist is consulted.
- If filters do not resolve it, reduce power or use a directional antenna as a temporary accommodation while further steps are arranged.