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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 10th Oct 2020, 9:24 am   #1
sexton_mallard
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Default Transmission on SW...what is this?

There are several of these transmissions across the SW bands which have been running for years and I have no idea what they are. I thinking possibly Radio Mondale or radar. They all have the same whirring noise suggesting a common format or protocol. Here is a link to a short YouTube video of this noise at around 41m.

https://youtu.be/iyOvxIkMsw0
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Old 10th Oct 2020, 9:33 am   #2
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Default Re: Transmission on SW...what is this?

That sounds rather like a facsimile (fax) transmission- I think the periodicity of the whirring is framing pulses, the regularity is implicit of a test pattern or ident (perhaps!). The HF bands used to be alive with these signals outside the regular amateur and broadcast bands. Maybe the fact that I'm surprised at other people's puzzlement is starting to betray my age....

Used to be used by the likes of news agencies to transmit pictures, also for things like weather information.
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Old 10th Oct 2020, 10:00 am   #3
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Default Re: Transmission on SW...what is this?

Hellschreiber?

David
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Old 10th Oct 2020, 11:18 am   #4
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Default Re: Transmission on SW...what is this?

High speed RTTY - possibly military.
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Old 10th Oct 2020, 11:59 am   #5
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Default Re: Transmission on SW...what is this?

I reckon Pete is right, it's probably 'stanag 4285' or similar, a fast RTTY mode. Decoders are downloadable for free ont' t'internet. You'll need a receiver capable of SSB reception.
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Old 10th Oct 2020, 12:24 pm   #6
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Default Re: Transmission on SW...what is this?

I've been hearing stuff like this since I started on the SW bands in the late 60s. Never thought to ask exactly what it is - just another one of those "noises" that seem to have been on the bands forever.

However Andrew2's suggestion of "Stanag 4285" seems probably right - given it sounds much like this example: https://www.youtube.com/watch?v=u-CgZNJIAVs

Richard
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Old 10th Oct 2020, 6:55 pm   #7
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Default Re: Transmission on SW...what is this?

Thanks! Seems the mystery is somewhat solved. NATO STANAG 4285 it must be then. Here is another recording from my Bush BS35 domestic radio in which two or more sources appear to transmit two bursts then pause for the next transmission in a cycle. The transmitters appear to be at different distances. Please ignore the continuous PLC adaptor put-put-put and ticking clock in the background.

https://youtu.be/D36XA3h6cKE
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Old 10th Oct 2020, 7:47 pm   #8
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Default Re: Transmission on SW...what is this?

My favorite data sound is piccolo https://www.sigidwiki.com/wiki/Piccolo still used upon occasion by amateurs for fun.
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Old 10th Oct 2020, 7:47 pm   #9
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Default Re: Transmission on SW...what is this?

Reminds me of when I worked a RAF Brampton HF RX station, our job was to monitor HF RTTY transmissions from places like Belize, Cyprus and Hong Kong. Mostly done by ear, if the reception was deteriorating we used the RA17s to find a suitable frequency then message the far end to ask them to change frequency. Wed then retune the Marconi MST rxers and wait for it to come up. We had to colour a chart in for each station, green or red in 15 min segments.
If you werent concentrating or fell asleep! It was easy to loose contact.
Its not me on the photo, probably taken in 1980.
Happy days.

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