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Author Topic: UNID FSK 27550 USB 1436 UTC 30 DEC 2022  (Read 248 times)

Offline ButchKidd

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UNID FSK 27550 USB 1436 UTC 30 DEC 2022
« on: December 30, 2022, 1615 UTC »
This may be futile given how many types of low-powered wireless devices use 27 MHz, but hopefully this being outside the ISM portion of 11m might narrow it down.

This morning, I'm hearing several FSK signals centered around 27.552 MHz.  They're either short bursts, or more likely, fading in and out.  I noticed them here locally in the Southeastern US, and the same or similar signals were on a couple Northeastern SDRs I checked, too.  It looks like about 250 KHz, which isn't a spacing I'm familiar with.  Sometimes I just hear one signal at a time, and sometimes there are two or three at slightly different frequencies.

Here's a recording and screencap from one of Sigma's Kiwis.

Link to recording:
https://archive.org/download/11m-fsk-2022-12-30-t-14-36-20-z-27550.570-usb/11m-FSK_2022-12-30T14_36_20Z_27550.570_usb.wav

eQSL appreciated at x100rocks@gmail.com
Airspy HF+ Discovery, Yaesu FT-857D and FT-450D, Whistler TRX2
130 ft OCF, 130 ft inverted L, 11m ground plane

Offline radiogaga

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Re: UNID FSK 27550 USB 1436 UTC 30 DEC 2022
« Reply #1 on: December 30, 2022, 1706 UTC »
This is what I'm seeing locally: seems to be burst every 9-10 seconds


A FB user from MX was wondering the same: Mauro Veiga
 
 
Eventually I hear RTTY signals at 27550. These are short duration signals with an unusual 250hz shift.  They look like a short sequence of letters.  Someone knows what it is?

rgg

Offline ButchKidd

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Re: UNID FSK 27550 USB 1436 UTC 30 DEC 2022
« Reply #2 on: December 30, 2022, 2148 UTC »
Thanks, Gaga!  I'm not on Facebook very often, so I missed that.  One of the commenters seemed to think it was Barrett Selcall which does sound similar, except it uses the more common 170 Hz frequency shift, and transmissions last about twice as long as these bursts.

I assume it's some sort of organized system of transmitters.  Transmissions were all the same duration, and when there was more than one signal at once, they began roughly at the same time similar to FT8 or JS8Call, but with longer pauses between frames.
eQSL appreciated at x100rocks@gmail.com
Airspy HF+ Discovery, Yaesu FT-857D and FT-450D, Whistler TRX2
130 ft OCF, 130 ft inverted L, 11m ground plane

 


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