Starting last night I began receiving strange signals in the 80-88Mhz region of the spectrum on my SDR. If I use FM demodulation, I hear a strong 60Hz component and a very weak voice. These signals are numerous across this range, most are short lived (a few maybe 10 seconds but some persist). These frequencies used to be occupied by television channels 5 and 6 but they've been moved to UHF. This is just outside of Seattle, Washington. These are extremely unstable in terms of frequency, I would suspect some CB'ers linear had a bad parasitic oscillation if it weren't for them being so numerous across the 80-88Mhz and they go right up to 87.9 Mhz but do not encroach on the 88-108Mhz broadcast band which suggests they are very intentionally generated. Any ideas?
