Many thanks to SWLing Post contributor, Carlos Latuff, who shares the following:
I bought a small analog radio and I’ve been listening with it.
On September 4, around 17h48 UTC, I heard a strange signal on the band of 13 kHz, since it’s not a digital dial, I don’t know precisely the frequency but maybe if your readers may listen to the signal they may tell what it is about.
It almost sounds like the preamble to an SSTV message, but I’m not sure about that noise that’s in between. Readers, if you can help Carlos ID this signal, please comment!
Sound file does not seem to be working
Sounds like RTTY to me. RTTY appears here and there throughout the HF band. Most of it is encrypted though.
That’s most likely an EAM on 13.201(USAF GHFS) using ALE.
At 13.5xx, you could be hearing any sort of industrial/scientific/medical emission since you’re at or near the ISM band. There’s all sorts of noisy things in that area!
In fact, it’s 13000 khz and not 13 khz, my mistake, gentlemen.
The pointer on the radio is at approx 13,2 MHz assuming theradio’s IF is 450 kHz the LO (local oscillator) will be running at 13,65 MHz this will mix to produce an image frequency of 14,1 MHz In that part of the 20 metre amateur band where one will find amateur digital activity.
Could it be that Carlos was in the close proximity of a digital minded radio amateur ?
I believe the frequency should be in MHz according to the radio is in the 22-meter selection. I also believe that the transmission sounds like Naval Fleet Broadcast in FSK. The frequency 13.200 MHz is listed in a Monitoring Times document on the same subject as Fleet Broadcast. I was a radioman in the Navy in the early ’70s and it sounds like the Fleet Broadcast.
Sounds like RTTY possibly. Here is a link to some samples http://www.w1hkj.com/FldigiHelp-3.21/Modes/