I did a FCC search, but found nothing. The NTIA allocation just says
fixed. I'll check the redbook.


Ron Baker, Pluralitas! wrote:
It is transmitting right now.

I regularly pick up an unusual data signal
at 15937.5 kHz (USB). It is 7 fsk signals stacked
in frequency. They are 170 Hz shift and there
is 170 Hz between them. The Baud rate is 75.
All seven channels send the same bit stream
but offset in time by as much as 6.66 seconds.
The bits show a flat autocorrelation.
Anybody know what this is/ who is sending
it?

--
rb

For the feds, the band can be fixed or any mobile except aero. For the
rest, it's fixed.
wrote:
I did a FCC search, but found nothing. The NTIA allocation just says
fixed. I'll check the redbook.


Ron Baker, Pluralitas! wrote:
It is transmitting right now.

I regularly pick up an unusual data signal
at 15937.5 kHz (USB). It is 7 fsk signals stacked
in frequency. They are 170 Hz shift and there
is 170 Hz between them. The Baud rate is 75.
All seven channels send the same bit stream
but offset in time by as much as 6.66 seconds.
The bits show a flat autocorrelation.
Anybody know what this is/ who is sending
it?

--
rb

wrote in message
oups.com...
For the feds, the band can be fixed or any mobile except aero. For the
rest, it's fixed.

Thanks for checking. I checked WUN logs and found
nothing.

I tend to think it is commercial but it could be military
(or diplomatic). The FDM aspect is definitely a
diversity thing, to overcome atmospheric fading.
All channels carry the same data. If fading temporarily
wipes out one channel the data still gets through.
There are numerous single channel 850 shift 75 Baud
fsk signals out there. I'm guessing they are military.
HF has notorious fading so I imagine they use
a diversity scheme too but with the parallel channels
spaced out over MHz, not just in one voice width
band. Being the military they have all sorts
of resources so they can use such widely spaced
frequencies. This FDM FSK thing requires less
coordination in setting it up yet still offers
some diversity and immunity from fading.
But the more modern way of doing that is with
OFDM, so this signal is kind of unusual.
It is modern primative.

--
rb


wrote:
I did a FCC search, but found nothing. The NTIA allocation just says
fixed. I'll check the redbook.


Ron Baker, Pluralitas! wrote:
It is transmitting right now.

I regularly pick up an unusual data signal
at 15937.5 kHz (USB). It is 7 fsk signals stacked
in frequency. They are 170 Hz shift and there
is 170 Hz between them. The Baud rate is 75.
All seven channels send the same bit stream
but offset in time by as much as 6.66 seconds.
The bits show a flat autocorrelation.
Anybody know what this is/ who is sending
it?

--
rb

wrote in message
oups.com...
For the feds, the band can be fixed or any mobile except aero. For the
rest, it's fixed.

I found another signal with the same modulation
at 7991.5 kHz. It is transmitting now at 1545 UTC
while there is nothing at 15937.5.

--
rb

wrote:
I did a FCC search, but found nothing. The NTIA allocation just says
fixed. I'll check the redbook.


Ron Baker, Pluralitas! wrote:
It is transmitting right now.

I regularly pick up an unusual data signal
at 15937.5 kHz (USB). It is 7 fsk signals stacked
in frequency. They are 170 Hz shift and there
is 170 Hz between them. The Baud rate is 75.
All seven channels send the same bit stream
but offset in time by as much as 6.66 seconds.
The bits show a flat autocorrelation.
Anybody know what this is/ who is sending
it?

--
rb

I found some experimental licenses near 15937.5, but not close enough
to be what you are hearing. However, it might pay look at them as maybe
your interpretation as to where they are located is not on the money.
It can be a bit confusing, but the FCC often specifies where the peak
energy is located, not where you would tune your radio. For example, in
sideband, there is no energy at the carrier, but the radio is designed
such that you tune to where the carrier would be if you had one.

If you never searched the FCC, go he
http://svartifoss2.fcc.gov/reports/index.cfm
Use the "frequency" search, and keep it narrow, maybe 1Mhz around where
you think the signal is located. Search both the universal licensing
and the experimental.

Ron Baker, Pluralitas! wrote:
wrote in message
oups.com...
For the feds, the band can be fixed or any mobile except aero. For the
rest, it's fixed.

I found another signal with the same modulation
at 7991.5 kHz. It is transmitting now at 1545 UTC
while there is nothing at 15937.5.

--
rb

wrote:
I did a FCC search, but found nothing. The NTIA allocation just says
fixed. I'll check the redbook.


Ron Baker, Pluralitas! wrote:
It is transmitting right now.

I regularly pick up an unusual data signal
at 15937.5 kHz (USB). It is 7 fsk signals stacked
in frequency. They are 170 Hz shift and there
is 170 Hz between them. The Baud rate is 75.
All seven channels send the same bit stream
but offset in time by as much as 6.66 seconds.
The bits show a flat autocorrelation.
Anybody know what this is/ who is sending
it?

--
rb