Tag Archives: Mystery Signals

Can you help Rob identify two mystery signals on the 20 meter band?

I received the following message from my buddy Rob (NC0B) who is trying to identify a couple of signals on the 20 meter band. Rob kindly gave me permission to post his email here on the SWLing Post with the idea that someone may be able to help him solve this:

The following is a description of two odd digital signals observed on 20 meters with transmission modes I do not understand. They may not amateur transmissions, but I have no way to decode them. They stick out like a sore thumb on 20m in the Extra portion of the phone band. The time of day on August 20th was between 11:50 AM and 12:00 PM MDT.

Two weeks ago I was in QSO on 14,170 kHz and occasionally there was the same 10 kHz wide digital signal but centered on 14,171 kHz. It sounded like the old Russian jammers buzz saw modulation. Those signals from decades ago were much wider, and or course we didn’t have high resolution spectrum scopes back then. Today the same transmissions occurred several times, and more than once a minute for about 5 seconds each. In total the transmissions may have occurred on and off for about 10 minutes.

Then after a few 10 kHz transmissions a different signal came on the air a few times with what looked like a digital modulated carrier plus digital sidebands on each side of the middle signal.

Look at the attached JPG file and I’ll try to make sense out of it:

The waterfall image lasts about 50 seconds on the Icom IC-7610 set on slow. There are two different signals to differentiate in this image. The signal I observed two weeks ago and today is 10 kHz wide and today spans from 14,178 to 14,188. It shows up in green on the band scope, and just under it in blue on the water fall for about 3 seconds of the approximate 5 second transmission. You can also see at the bottom of the waterfall the previous transmission that has about 4 seconds worth saved on the waterfall running off the bottom. The horizontal span of the scope was set to 5 kHz per division.

Once the 10 kHz wide signal started, I went to Dual Watch so I could listen for KL7QOW on 14,170 kHz for a sked, and hear the buzzing signal on 14,183 kHz in SSB mode. That frequency placed the carrier position of the SSB 2.8 kHz bandwidth in the center of the 10 kHz wide signal.

Soon after I started observing the relatively flat spectrum of the 10 kHz signal, a new digital signal appeared about 3 kHz lower in frequency. At first it had a much stronger center modulated carrier about 2 kHz wide and then two symmetrical digital signals on each side within about a 6 kHz total bandwidth. I wasn’t able to capture the best picture of the 2nd signal as it appeared to be tuning up. The amplitude difference between the central signal and the separate sidebands initially was about 15 dB. Vertical divisions are 10 dB.

On the waterfall you can see the second type of signal is centered on about 14,180 kHz. The modulation depth of the outer pairs of signals were not constant, possibly due to selective facing. QSB was quite significant at this time at least to Alaska. You can see there was a short break of a few seconds in the 6 kHz wide signal. Every time I have seen the 10 kHz wide signal its amplitude across the transmission bandwidth has been fairly constant, always of short duration, and repeating several times within 10 minutes before terminating.

Does anyone have any idea what either of these transmissions are? I have heard of email digipeaters, but I would not think their bandwidth would be this wide.

Rob, NC0B

SWLing Post community: Please comment if you can help Rob ID these signals!

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Patricia hears a mystery signal on 7075 kHz

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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?

Thanks,

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

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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?

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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?

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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?

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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

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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:
https://capespectrum.wordpress.com/hf-marine/

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