Tag Archives: Mystery Signals

Can you help Bruce identify this shortwave noise?

Many thanks to SWLing Post contributor, Bruce (VE6XTC), who is trying to identify noises he’s hearing on the HF bands. Perhaps readers can help.

By request, Bruce has provided me with two recordings via his Kenwood TS-440S:

Recording 1: 7,335 kHz at 0500 UTC on September 13, 2020

Recording 2: 7,405 at 0500 UT on September 13, 2020

Post readers: If you can help Bruce by identifying these HF noises, please comment!

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Carlos seeks help identifying a signal

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

Hope this message will find you well.

I just monitored in Porto Alegre, Brazil, this signal on 9460 kHz. Searching on Internet I found that it’s the same frequency where the Russian MR-102 Baklan radar is operating. But it could be a weather fax. Do you have any clue?

Please, check attachment for the audio clip. Thank you in advance.

Thank you for sharing this, Carols. To my ear it does sound like some sort of slow-scan digital mode like weather fax, but I’ll leave it up to the SWLing Post community to help identify.

Post readers: please comment if you can ID this signal for Carlos.

UPDATE: Nils Schiffhauer found the answer. The signal is a weather fax transmission most liekly from Wellington, NZ.

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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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