What type of signal is this?

machineghost

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Hi All, I have come across a waterfall pattern that I'm not familiar with.
It looks like an LSB fax transmission.
Does any know what it is please?

Thank you
 

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spongella

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Yes, a recording would help. A wild guess would be Link-11. Got to sigidwiki and compare.
 

dlwtrunked

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As a general rule, one needs both a waterfall and a sound file. On HF as a general rule, it only one, it needs to be a sound file.
Yes and the frequency.
 

machineghost

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Hi All, thank you for your responses. Here is the sound file. It looks and sounds like it is changing frequency. When I use SDR Sharp the frequency shifts right of center. Frequency is 505.958.200. Thanks.
 

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nd5y

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It's probably interference from some electronic device in your house or nearby. Maybe even created by the SDR itself.
 

dlwtrunked

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Hi All, thank you for your responses. Here is the sound file. It looks and sounds like it is changing frequency. When I use SDR Sharp the frequency shifts right of center. Frequency is 505.958.200. Thanks.

Sounds like that was recorded in AM mode--always need a single-sideband recording to analyze below 30 MHz. I do think ND5Y is correct and that it is probably interference.
 

jwt873

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I listen quite often for non directional aviation beacons between 200 kHz and the start of the AM broadcast band at 540 kHz. I also sometimes decode digital signals on the 630 Meter ham band (472–479 kHz).. I've been doing this for years and have never seen anything like what you've posted.

As mentioned above, it could be local noise. Is the sound always there at the same strength? Or does it vary by time of day? Where are you located?
 

machineghost

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Jan 12, 2021
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Thanks nd5y and jwt875. Spot on. Interference from my powered usb hub. As soon as I unplugged it a few spikes that were similar on the waterfall disappeared.
 
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