3.440mhz scrambled transmission

Greetings,

Discovered this weirdness below the 80m Ham Band while SWL'ing for Echo Charlie stations. It appears to be some form of scrambled transmission. SWL'd Oct 17, 2340hrs.

Any suggestions?

Category:

Entertainment

Tags:

• Ham
• Radio
• SWL
• DX
• Scanning
• Amateur

[mw3rmr]

thats called thob, its a digital mode of transmission, there are many kinds that hams use, eg psk fsk packet amtor, google or you tube it and you can see it in action

73 De MW3RMR

[TheTripleSixer]

Cheers for the bonus info.

It was a damn weird find. Don' you just love HF :-)

[Robin814]

Good find, Mark!

[TheTripleSixer]

Indeed,

Got to love HF man, there is tonnes of really weird stuff there. This was an accidental find as I was just tuning through the 80m ham band at the time and went too far back.

[RayAir1]

thob? It is FFT scrambling.

[RayAir1]

Probably a military net because you can hear the ALE.

[RayAir1]

That is a transform based scrambler (FFT). It is based on linear transforms of the speech signal. I believe it uses a 256-point FFT transform. If you put the signal on a spectrogram you can see how the voice is broken up over the audio spectrum. Good FFT scramblers do not use a constant transform, but vary the scrambling scheme 8-10 times per frame with each frame being 16-60ms. It offers very good security against most every listener.

[battlestarone]

there oil rigs,some oil firm still use hf to contact there oil platforms,they encode the audio by a method called invertion i think,with the right software i beleave you can decode this,or so i am told.

[TheTripleSixer]

Nope,

It's defo encrypted millitary transmissions dude. Top answer though, lmfao!