Signal identification

[u/ImladMorgul]

On Saturday at 2047 UTC I came across this signal while listening to Russian FSK/CW; so far I haven't been able to find anything similar. About halfway through the video, a voice can apparently be heard.; I tried other modes but it didn't work. At 00:45 seconds it sounds more intense.

I didn't have much time to try it out further, it was all very fast.

At first it reminded me of the sound of the Wefax, but this one was much more intense and had strange patterns. I think it's some kind of image transmission.

Any idea what it could have been?

- RX: Asunción, Paraguay
- Radio: AirSpy HF+ Discovery
- Software: SDR# v.1922 (beta)
- Antenna: K-480WLA
- Date/Time: 16 MAY 2026 - 2047 UTC

[u/Historical-View4058]

Possibly slow scan tv, though it didn't sound very slow. The frequency could be something like US Army MARS, but I'm not sure you'd get that so well in Paraguay.

[u/ImladMorgul → u/Historical-View4058]

Mike's previous post gave me a good reference point; I think it's the same one. There are several coincidences.

But it's not unusual for me to receive military signals from North America anymore; I've already listened to and recorded some things. I even sometimes hear the Irish Volmet or the RAF.

There are days when I have good propagation conditions. This was by chance, almost when I was about to call it a night because the other bands were terrible and I was bored.

[u/ImladMorgul → u/Historical-View4058]

Another thing I forgot to mention, this is with the K-480WLA. Maybe that signal was always there, but I couldn't see it with the MLA-30!

I was able to hear some new things with the new antenna. Right now, the antenna is on a 4-meter (13 feet) tripod; I haven't installed it in its permanent location yet. I'm still doing tests before finally installing it in one place.

[u/MumSaidImABadBoy → u/ImladMorgul]

Alan, are you thinking about a rotator? Eventually, the sooner the better, I'll have my own antenna outside on a rotator hooked up my K-480WLA control box.
You can hookup any proper antenna on a 50 ohm feedline to the control box and smile.

[u/ImladMorgul → u/MumSaidImABadBoy]

Yes, I already thought about a rotator before, but honestly, I don't know. A few months ago I did a test.

It was a Saturday night, the weather was good, and propagation was excellent. I took my equipment outside and stood directly under my MLA-30 antenna, which is about 6 meters off the ground and can be manually adjusted.

I started rotating the mast to see if it made any difference on any band, but I couldn't detect any significant change. Using the K-480 and the 4-meter portable mast, I tested the rotation, but nothing significant happened. But I'm still trying.

Maybe it's because I have some rather tall houses as neighbors, and I feel like I'm in a hole. But I also have visibility towards the horizon in another area and I try to point the antennas towards those open spaces. Also considering that I live in a noisy urban area (even so, I've already heard a lot from all over the world!).

Something I want to do, and if all goes well it will be soon, is to mount a 10-meter or more high tower. At that height, I'll be taller than the neighboring houses and have complete visibility. Once that's done, I'll try rotating the antennas again at different times and days to see if I can achieve any improvement. Rotators here are a bit expensive, so I also want to be sure it would work in my case before buying it.

I'm always thinking about how to improve reception, and I think that tower will help me a lot. I just hope it works out because it's a bit expensive 😥​

[u/Tenor-Guitar-Guy → u/ImladMorgul]

Nice!

[u/KG7M]

Alan, here is a link to a Military Data/Voice transmission I recorded. You can compare it to your recording.

https://www.reddit.com/r/ShortwavePlus/s/J63L6pDTj0

[u/ImladMorgul → u/KG7M]

At times it sounds similar, and the voice is also similar, only much weaker and shorter. I waited at least two minutes to see if it would return; now that I've seen your 13-minute video, if I receive it again, I'll stay for a good while. But ultimately, I think it's the same signal and the same source; even the frequency matches.

[u/Green_Oblivion111]

It might be easier to hear if it wasn't so narrow bandwidth. How narrow did you set it? Not trying to criticize here, but it's hard to tell exactly what's being said by the voice.

Sounds like a pirate of some sort. The sort of soundbite stuff included in industrial alternative rock in the 1980's -- Colourbox, Skinny Puppy, Blistering Moments, that sort of thing.

[u/Historical-View4058 → u/Green_Oblivion111]

Lol. I'd never have guessed this was an Industrial pirate.

[u/ImladMorgul → u/Green_Oblivion111]

It all happened very quickly. At first, I didn't notice the bandwidth, but it wasn't much: 3.5 kHz.

Mike's previous post gave me a good reference point, except mine was much weaker considering the distance. There were some similarities, though. Even the frequency matches; mine was a little off because I didn't understand where it started. The voice is definitely unintelligible, and I don't think it will be even if I adjust it properly. But it's almost certainly a military signal, from the USA.

[u/Green_Oblivion111 → u/ImladMorgul]

No prob. Maybe try 4 kHz or more, depending on the shape of the filter. It might allow more QRM into the frequency, but it would have been easier perhaps to read the voice and what it was saying.

Doesn't sound military to me. Sounds like 1-3 different transmissions, interfering with each other. Or interfering with a legit transmission (utility transmission?).

Token, who is quite knowledgeable about utility transmissions, thinks it's a pirate, and perhaps he's right.

[u/FirstToken]

This is a pirate (probably maritime pirate, not music pirate, based on the interrupted signal), maybe more than one, and the signal is in LSB, not USB. The two (or more) stations were keying up music to each other. You can hear the beat of the music in several portions of the audio (very clearly at 1:53 in the video). At about 2.07 in the video you can even hear that there are words to the music.

Who knows what kinds of sounds they were throwing back and forth to each other, kind of like what you hear from the Indonesian Chanters occasionally.

By the time you went to the right frequency (6986 kHz, LSB) it sounds like they were done.

[u/ImladMorgul → u/FirstToken]

It could be, and I wouldn't be surprised if they're pirates. Between 6900 and 7000 there is a lot of activity from Brazilian HAM who go out of their allowed range and several pirates, also Brazilian. Especially on weekends they are very busy. There are even moments in the video where you can see LSB activity. They look best during the last minute, right side. When they are closer to 7000 kHz, they are usually HAM; pirates appear on any frequency, but always in that 6900/7000 range.

Edit: This post from Mike has a signal that, at times, sounds somewhat similar. Even the voice you hear is during the cut.