Unknown signal

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An Electrocardiography-like signal
Capture 1.png
Frequencies 24.574 MHzMegaHertz (MHz) 10^6 Hz24,574,000 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz).
24,574 kHzKiloHertz (kHz) 10^3 Hz
,147.455 MHzMegaHertz (MHz) 10^6 Hz147,455,000 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz).
147,455 kHzKiloHertz (kHz) 10^3 Hz
Frequency Range 24574000 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz).24,574 kHzKiloHertz (kHz) 10^3 Hz
24.574 MHzMegaHertz (MHz) 10^6 Hz
147455000 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz).147,455 kHzKiloHertz (kHz) 10^3 Hz
147.455 MHzMegaHertz (MHz) 10^6 Hz
Mode USBUpper Side Band Modulation (Radio, referring to reception and modulation mode)Universal Serial Bus (Computer, referring to USB Ports and cables)
Modulation unknown
Bandwidth 70 kHzKiloHertz (kHz) 10^3 Hz70,000 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz).
0.07 MHzMegaHertz (MHz) 10^6 Hz
70 kHzKiloHertz (kHz) 10^3 Hz
0.07 MHzMegaHertz (MHz) 10^6 Hz
70 kHzKiloHertz (kHz) 10^3 Hz
0.07 MHzMegaHertz (MHz) 10^6 Hz
Location worldwide
Short Description an unknown signal on the HFHigh Frequency (3-30 MHz) band, repeated on the VHFVery High Frequency (30-300 MHz). A carrier modulated with a short burst of rumbling sound every 2 seconds, transmitted non-stop 24/7.
I/Q Raw Recording
Audio Sample

An unknown signal, which was received with an RTL-SDR dongle and SDRSharp, have an appearance of an electrocardiography or seismometer with short pulses every 2 seconds on the waterfall diagram. it was suggested that the signal came from the dongle itself. However, the signal disappeared when the receiver's location was moved approximately 20 km away. It is also speculated that the signal transmitted from a nearby airport, because the closest airport is only a couple of miles away from the original location of the receiver, suggesting that it may possibly a radar or any sort of aircraft navigational aid. The signal appeared at two different frequencies, the first one is on the HFHigh Frequency (3-30 MHz) band, at 24.574MHz and the same signal appeared on the VHFVery High Frequency (30-300 MHz) band, at 147.455 MHzMegaHertz (MHz) 10^6 Hz, with a carrier signal modulated with a short, random burst of low frequency rumbling sound with 70 kHzKiloHertz (kHz) 10^3 Hz bandwidth every 2 seconds, transmitted non-stop 24/7.