Tag Archives: Mystery Signals

Patricia hears a mystery signal on 7075 kHz

Many thanks to SWLing Post contributor, Patricia, who writes with the following inquiry:

I wonder if anyone has heard and identified the station or signal I heard on 7075 kHz at 0745 October 30, 2021 on my C. Crane Skywave, and I live in southern California. I would like to know where this signal originates, sounding something like a numbers station, no voice, but a whooshing sound. I have heard it may be a ham frequency or a signal from space. Any ideas?


Patricia G.

Thank you for your question, Patricia.

I believe what you’re hearing is the ham radio digital mode called FT8.

FT8 is a weak signal digital mode that is extremely popular in the ham radio world these days. The mode isn’t designed around relaying lengthy messages, rather it’s designed for short, very formulaic exchanges.

Each message of up to 13 characters takes 13 seconds to send. For FT8 operators to be successful, they try to keep very accurate timing on their computing device controlling the transceiver. When the whole group is coordinated well, you’ll hear groups of signal tones singing all at once in 13 second intervals with a couple seconds of space between messages.

Here’s what FT8 sounds like in SSB mode:

It’s possible it sounded quite different, however, if you were listening in AM mode.

If this doesn’t sound like what you heard, perhaps you can check the comments for any other possibilities, but my guess is it’s FT8 as it’s a pretty strong chorus of tones!

Great question, Patricia!

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Help Carlos ID this mystery digital signal

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!

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Five Beeps: Can you identify Carlos’ mystery signal?

Many thanks to SWLing Post contributor, Carlos Latuff, who writes from Brazil:

[Please check out this] audio sample of a signal I heard today (July 20, 2021) around 07h17 UTC on (at least) 4 different frequencies, simultaneously:

– 16166 kHz
– 16716 kHz
– 16747 kHz
– 16839 kHz

Always the same. Five beeps repeating in intervals of 30 seconds. 
Another mystery to be solved by your readers.

Thank you for sharing this, Carlos. Hopefully, a reader can comment and ID these beeps for us!

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Can you ID these HF transmissions?

Many thanks to SWLing Post contributor, Carlos Latuff, who shares the following video of sounds he heard on HF. Carlos adds, “Are we in the Twilight Zone or Lost in Space? They sound like effects from a 60’s/70’s sci-fi movie!

Those sounds are wild! The stuff of Star Wars.

My only guess is that it’s a form of OTH RADAR? I’m sure an SWLing Post reader will sort this out in short order! Please comment!

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Can you ID this ham radio digital signal for Rob?

Many thanks to SWLing Post contributor, Rob, who writes:

I have a question about the digital signals I received today during what must have been an E skip opening to the southwest.

Can you identify by the bandwidth the wide signal in one screen capture vs. the normal FT8 signals which were decoding today quite well using the 7610?

Typical 6 meter band FT8 signals

Wide digital signal on 6 meters.

The wide signal didn’t decode in FT8 mode, but I have no idea what mode was being transmitted. Any idea?

Great question, Rob. I’m posting this because I’m no expert on timed digital mode signals. I recognize FT8, and assume this could be FT4, JT65 or similar, but the timing is identical to FT8. I’m sure someone in the Post community will solve this signal mystery in very short order!

Readers: Can you help Rob ID this wide, timed digital mode signal? If so, please comment!

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Carlos seeks clarity about another CW station

Many thanks to SWLing Post contributor, Carlos Latuff, who writes:

Today (June 5, 2021) I heard another mysterious CW transmission here in Rio Grande do Sul coast, this time on 8779 kHz, 18h31 UTC.

I did some research and this frequency is related to Rome Radio (which is no longer transmitting in CW) and a marine channel (ITU821) related to Cape Town Radio but I’m not sure:

I’m sure your readers will solve this puzzle as well.

Thanks for sharing, Carlos!

Post readers: Can you help Carlos ID this station? Please comment!

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Can you help Carlos identify this CW station?

Many thanks to SWLing Post contributor, Carlos Latuff, who writes:

Hey Tom,

Check out this recording.

I heard it today on 16976 kHz USB, at 13h08 UTC, here in Tramandai coast, Rio Grande do Sul, Brazil.

Maybe your readers may have an idea what is this CW about?

Thank you for sharing this, Carlos!

Post readers: If you can ID this station, please comment!

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