Can Anyone guess this mode?

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  • Updated 3 years ago
I hope you guys don't think this is hopelessly off topic, but I thought someone out there might know...

I have come upon an intriguing transmission mode on 40 meters - both on 14.377 and 14.416 - on the waterfall it has a 2.7KHz width pattern, most reminiscent of one of those twisters (twisty licorice candies). On USB it has a whooshing sound, like a plane is just close enough to make out a faint noise as it circles endlessly. The sound is a constant stream with some slight fading at regular intervals. I can't figure out what mode it might be - I considered SSTV, but the software I have thrown at it shows only noise?

I was thinking that it is most likely some form of telemetry, but I can't find any sound samples that come close to it.

Any ideas?

Thanks!

73,
Roy, AC2GS
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Roy Laufer

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Posted 3 years ago

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Ross - K9COX

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ET phone home
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Ken - NM9P, Elmer

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Compare it to the Easypal users on 7.173 and 14.236.  Does it sound similar?
It may be a kind of digital data exchange mode.
It could also be multi-channel multiplexed RTTY of sorts.

Ken - NM9P
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Roy Laufer

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Stu Phillips - K6TU, Elmer

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Keep an eye around 14.236 - this looks very similar to the waterfall pattern of FreeDV...  I know there are MARS frequencies either side of 20m - but I don't know exactly what they are and I have no idea whether MARS uses any kind of DV encoder.

But the pattern is strikingly similar!
Stu K6TU
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Michael - N5TGL

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I can't tell you about the mode in use, but I can tell you about the circling whooshing sound you are hearing.  The waterfall is showing classic Rayleigh fading as a result of ionspheric propagation.  You can think of it as you being able to see what the ionosphere is doing as it swishes around up there.

http://en.wikipedia.org/wiki/Rayleigh_fading
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Jay / NO5J

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Wow, I learn something everyday.
Need to learn how to explain it to some of the nonlearners, for them there is only one explanation and I don't know that one, and hope I never learn it.

Thanks for the link to the article!
73, Jay - NO5J
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Michael - N5TGL

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Glad to help out, Jay.  I was pretty amazed when I was first told also!
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Stu Phillips - K6TU, Elmer

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I suspect its digital encoded voice using some form of codec.

If watch around 14.236, you will see FreeDV transmissions - see if they look similar.

Stu K6TU
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Ken - NM9P, Elmer

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oops... I got my freq. wrong.... The 20 Meter EasyPal frequency is 14.233.  Stu is right 14.136 is the FreeDV frequency.  They sound very different from one another.   BTW...I can hardly wait until the FreeDV API is released to give us native DV on the 6000!

Ken - NM9P
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Bob G W1GLV

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 Ken, FreeDV freq is 14.236 mhz
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Barry-W4TGA

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Perhaps this is the signature of the NY/MA military contractor that had obtained an experimental license that included much of the HF spectrum.


73,
Barry, W4TGA
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Stu Phillips - K6TU, Elmer

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The MITRE Experimental license is for very broadband digital signals.  I hope they keep clear of the HF ham bands!

I've seen stuff just above the top end of 20 that looks like digital voice - similar pattern and a bandwidth of 2-3 KHz.

The MITRE license I believe talks about 100's of KHz up to over 1 MHz!

Stu K6TU
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Jay / NO5J

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I think I've seen your Woosher on 40m It creeps around a little usually down in the noise level, drifts thru my passband at random times, its noisy and slightly annoying, I figured it was just propagation effects on a distant SW AM broadcast just barely emerging out of the noise floor. Never seen it have a carrier with it so its probably not an AM broadcast. Others in the Ragchew net have reported hearing it while I am, so it's not local noise. The fact that it moves slowly back and forth on the panadapter makes me doubt it's anything but QRN how would intended listeners find it and follow it. Maybe I should locate some Tin Foil, to make hats out of. Might be LGM.
73, Jay - NO5J
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Roy Laufer

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Я понимаю по-русски(I don't understand Russian)...