[Boatanchors] [Milsurplus] Strange Sound On Air- Data Burst?

[K0DAN]

There's a new one (new to me anyway) which moves around 28 Mhz and occupies 
50+ khz during each transmission. Transmissions last a few seconds, then 
appear to be answered on another frequency, slightly high or lower.

A screenshot can be viewed here: 
https://www.dropbox.com/s/atmqsoqe4zf22m9/2014-03-20_122037.jpg

-----Original Message----- 
From: J. Forster
Sent: March 20, 2014 11:51
To: David Stinson
Cc: boatanchors at mailman.qth.net ; boatanchors at theporch.com ; 
milsurplus at mailman.qth.net
Subject: Re: [Boatanchors] [Milsurplus] Strange Sound On Air- Data Burst?

There are sounders used to check propagation between sites. They send a
bit, measure S/N, skip to a new frequency, and repeat. Most often used for
things like embassy HF links, I think.

Maybe one of those?

-John

=============



> For years I've occasionally heard this sound on the bands:
>
> http://home.netcom.com/~arc5/pulses.wav
>
> It is not swept; it's specific to a frequency.
> Often, there is only one set of two pulses.
> Sometimes there are three sets, other times several more.
>
> I've been told these are data bursts sent from one RDF site
> to another, which replies.  These bursts are used to adjust
> the site calibration vs. real-time propagation, giving a more
> accurate RDF "fix."   I think this was the person's theory,
> rather than any certain knowledge.
>
> Does anyone have an idea?
>
> 73 DE Dave AB5S
>
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