Tag Archives: Mystery Signals

Can you help Carlos identify this 1982 polytone broadcast?

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

I have a tape with a recording I made in 1982 while listening to shortwave.

I’m not really sure if I caught some kind of polytone numbers station. Could you or your readers be able to identify it?

Post readers: If you can help Carlos identify this transmission, please comment!

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Can you help Bruce identify this buzzing noise from the 31 meter band?

Many thanks to SWLing Post contributor, Bruce Atchison, who writes:

I’m hearing an intermittent buzzing noise on 9820kHz each evening at around 4:00 UTC. What could it be?

Sorry the quality isn’t as good as I’d like, but here’s a recording:

Thank you for sharing this recording, Bruce.  My hope is an SWLing Post reader will be able to correctly ID the source. Please comment!

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Help Jim identify this mystery shortwave “time signal” station

Many thanks to SWLing Post contributor, Jim Meirose, who recently logged a mystery signal and is asking for our help to identify it. Jim notes that it sounds much like a time signal and can be found on 4,806 kHz.

Jim lives in the north east US and is receiving the station each morning between about 5:00 – 8:00 EDT (9:00 – 12:00 UTC). He shares the following video:

Based on Jim’s description, I thought this might even be a local noise, but after hearing the audio and since the signal is following morning propagation, I’m guessing the source could be in Europe or possibly regions further east–?

SWLing Post community: Can you help ID this station? Please comment!

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CPRM Lisboa: Another mystery signal solved

In response to our latest mystery utility signal challenge, SWLing Post contributor, Dean Bianco replies:

This is the musical marker for CPRM Lisboa, a radiotelephone terminal that provided overseas telephone and telegraph communications in the days prior to satellites.

I remembered the non-broadcast HF frequencies being loaded to bursting with many of these radio services. When not scrambled for privacy, one could hear a telephone call in progress. Instead of a musical IS such as this one, most were loop tape voice ID’s in several languages (almost always including English). So naturally these musical loops made it quite difficult to know what exactly one was hearing, to say the least!

To verify check out the following embedded audio file made by Willi Passmann  (via the excellent UtilityRadio.com website):

Once again, thanks to Dean Bianco for solving yet another mystery! Obviously, Dean is a Black Belt SWL and DXer!

FYI: I’ve received a number of emails from readers who really enjoy these mystery signals. Since we all seem to have more time at home these days, I’ll plan to keep them coming!


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Yet another mystery utility signal to solve–!

Back by popular demand!

On our quest to solve UNID utility signals, SWLing Post contributor David Crawford, is asking for help again to ID yet another interval signal. David writes:

Here’s yet another memorable utili-tune from the deep archives here, again not my recording, origin uncertain.

This one has a date, time and frequency on the filename [19670811-2347-15910-VM unID] and therefore would have been 1967. I heard this one myself occasionally also, which would have been sometime during the mid-to-late 1970s. It would have overlapped with the same time period during which CTNE was using the 14985 kHz tune previously provided, so despite the broad similarity I would assume it wasn’t them. Unless of course they used different tunes for different circuits:

Readers: Can you positively ID this interval signal? If so, please comment!

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Dean solves second interval signal mystery

(Image source: Madrid.org)

In response to our second mystery interval signal challenge, SWLing Post contributor, Dean Bianco replies:

Mystery solved!

This is the “interval signal” (more accurately, a placeholder with a musical station identifier) for the Compañía Telefónica Nacional de España (CTNW) from Madrid, Spain.

They were a point-to-point HF radiotelephone terminal that provided overseas telephone and telegraph services in the days before satellites became common.

As a young SWL, I would receive all manner of strange musical identifiers for these utility stations. Most of these HF telecommunication services had gone to satellite by the early 1980’s. The HF bands were chock-a-block with signals, whether they be broadcast or utility services.

Glad to help!

To verify his claim, Dean shares the following embedded audio file made by Willi Passmann in the mid 1970s (via the excellent UtilityRadio.com website):

Well done, Dean! Thank you once again for coming to the rescue!

In case you didn’t know, dear readers, Dean Bianco is a force to be reckoned with in the shortwave radio world. 🙂 This year, he won the 3rd Annual Fest Trivia Quiz at the 2020 Winter SWL Fest! An impressive accomplishment, indeed. Not only that, but Dean’s an incredibly nice guy, great friend, and always willing to help out those new to the hobby!

Thank you, Dean!

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Let’s solve another interval signal mystery!

Last month, we published a post asking SWLing Readers to help Brian (W9IND) identify an elusive interval signal. Turns out, the interval signal belonged to the Voice Mirror of the PTT Habana, Cuba station.

This month, SWLing Post contributor, David Crawford is asking for help to ID another interval signal which likely belongs to a utility station. David writes:

In follow-up to the La Habana utility mystery, here’s another one from the same era, 14985 kHz or thereabouts. Somewhere along the line I came to the conclusion that it might be El Salvador, but I don’t remember what led to that. The [recording embedded below] isn’t my own recording of it.

The tune is composed of individual DTMF tones, and when I was a bored youth I discovered that it could be played on an AT&T desk touch tone phone by pressing two keys at a time to remove the second tone. This one would repeat for hours at a time, interrupted by manually patched telephone calls.

Readers: Can you positively ID this interval signal? If so, please comment!

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