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Author Topic: Pulsating - feedback signal on 13236khz @ 0130 UTC 28/7/15  (Read 4596 times)

Offline mr magoo

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I came across this pulsating, feedback sounding type signal on 13236khz last night, 28/7/15 around 0130 UTC. The signal lasted a good hour or so before fading. Lots of QSB on this signal. I did the capture when the signal was its strongest using USB mode. I'm located in NJ, USA and this was using my Elad FDM S2 SDR with one of my dipoles at 35 feet.

www.youtube.com/watch?v=COHu5tbgte0


Any ideas on what this is or what mode it is?

Thank you.

Offline Token

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Re: Pulsating - feedback signal on 13236khz @ 0130 UTC 28/7/15
« Reply #1 on: July 29, 2015, 1713 UTC »
This signal is what is sometimes called XM (ENIGMA oddity designation), Backwards Music, or Whales.  Recently I also saw it called (tongue in cheek I am pretty sure) Backwards Whales.  There are several theories on what it is, ranging from encrypted traffic to simple feedback.

The signal can show significant variation from source to source.  Antenna bearings suggest many locations have been the source for this signal.  It is sometimes noted on USN frequencies, and so that is one theory for source, but it can also show on freqs the USN is not known for using.  If the signal is accidental that could confuse things even more, since it might be from multiple sources at different times and folks often try to tie a signal to one source.

This signal shows up periodically, and has for many years.  Sometimes it is on a freq for a few minutes or hours, other times it will be on a freq for days or even weeks.  It had been on the freq you recorded for at least 2 days before your recording.

Personally I think it is feedback, a transmitter or open microphone monitoring a receiver tuned to its own transmit frequency, either via a remote or local.  Although very uncommon, background noises have occasionally been noted on the signal.

T!
« Last Edit: July 29, 2015, 1718 UTC by Token »
T!
Mojave Desert, California USA

Offline mr magoo

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Re: Pulsating - feedback signal on 13236khz @ 0130 UTC 28/7/15
« Reply #2 on: July 29, 2015, 1834 UTC »
Thank you Token for all the great info.

 

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