Possible weather station sensor on air band

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Clock signal on air band
Unknown station.jpg
Frequencies 120 MHz
Frequency Range 120 MHz - 120 MHz
Mode AM, NFM
Modulation Unknown
Bandwidth 4 kHz,14 kHz
Location Central Czech Republic
Short Description

Three strong signals at 120MHz, in the air band.

Source of signal is unknown. Polarisation seems to be circular, as both vertical and horizontal dipoles can receive it at similar strengths.
I/Q Raw Recording
Audio Sample

The tempo of the signal changes, first time it was received it was very slow (two "beeps" per second), then it doubled in speed, and now it is almost continuous (as heard in the audio sample). There are no multiples of the signal at 240MHz or 480MHz. Signal is clearly artificial, there is a faint "clock" sound that ticks every second, very precisely, possibly for synchronisation. Possible sources are wireless weather station, city lighting sun sensor, unknown image transmission format or an unknown aviation navigation aid.


The main "clock" signal is roughly centred at 120Mhz (frequency may slightly differ due to SDR), accompanied by two signals of equal strengths; one 5138Hz lower and the other 5781Hz higher in frequency. The overall combined bandwidth of all three signals is 14kHz.