[GreenKeys] Strange RTTY Signal on 29.684

[Tim]

Geoff,

  I'm not on the list directly so I'm sending this direct to you as well 
as trying to send it to the list.


  You're pretty far away from the Bay Area for ground-wave, so assuming 
it truly is encrypted & thus not
amateur-radio related my semi-educated guesses for transmitter locations 
are:

1. Some sort of local Naval Post-Graduate School experiment, perhaps 
involving a USN vessel
off the coast or Santa Rosa/San Nicholas islands.
2. As someone else mentioned, some sort of temporary circuit coming out 
of Camp Roberts, Fort Hunter-Liggett or Camp San Luis Obispo,
however most Army/ARNG HF circuits these days are tactical in nature, 
and use Near Vertical Incidence Skywave on
HF between about 3 - 8MHz (& I disagree that CA ARNG is using Korean-war 
era transmitters/receivers these days).  Camp Roberts does
have a strategic comms activity, but as far as I know it's just 
satellite-based.
3. Something coming out of Vandenberg AFB/Naval Base Ventura County 
(NAWS Pt Mugu & Point Hueneme)
4.  A small site very local to you, such as an FAA or even a local telco 
that has HF for national security emergency preparedness/continuity of 
operations
plan.
5. Some sort of USG/DOD use of the former VOA Delano Relay Station.
6.  Something coming out of SRI's Wide Aperture Research Facility over 
the horizon-backscatter tx site near Lost Hills
7. The Navy's (contractor-operated) Naval Radio Station (Transmit) 
facility in Dixon, CA, which last-time I checked it out,
multicasted KG-84 encrypted fleet broadcast & NATO traffic out on about 
12 different channels from LF thru upper HF.  However,
you tended to rule out NASA/DOD at Vandenberg AFB because you're about 
150 miles away.  I'm guessing Monterey is at least
150 air-miles from Dixon...   Vandenberg does have HF, but nothing too 
elaborate or high-powered.   Collocated aboard the Navy's
long-time HF transmit site (first used by NAVCOMMSTA San Fran, then 
NAVCOMMSTA Stockton) is a USAF High Frequency
Global Communication System transmit site controlled by Andrews AFB -- 
mostly ground/air voice traffic but they do occasionally
do temporary DCS long-haul data circuits for customers.
8. The DHS/USCG Communications Area Master Station Pacific does have 
their local HF transmit site near Bolinas, at Point Reyes, just NW of
San Francisco & if they aimed one of their directional antennas SSE it'd 
point right at Monterey, mostly coming across the ocean.
9.  The former VOA Dixon Relay Station is now mostly used by Arinc.   
Arinc also apparently transmits a lot from the old Globe Wireless 'KFS'
receive site about 8 miles S of Half Moon Bay.  Arinc (used to be 
Aeronautical Radio, Inc.) does do HF data, and does have some special USG
contracts in addition to RDT&E of various HF waveforms & systems.


  If you're pretty sure it's to your North/NW & experienced enough with 
skywave/groundwave  to think it's a high-power station 100+ miles away,
#7 is probably the best bet.


  Just to be thorough, you should probably also go by USCG Station 
Monterey just to rule them out. They
do have HF, but not really any point to point type HF data circuits 
that'd be on the air continuously.


  That's about all I can think of.  Alas, the Bay Area no longer has a 
lot of military facilities, just as the US military no-longer has "a lot" of
high-ERP HF radio sites.  

  I won't argue with you about the science & magic of ground-wave, 
though in my experience, unless it really is a high-ERP transmitter or
an antenna system made for ground-wave, you've got to be within a couple 
miles of the transmit site to be strong, and maybe within roughly
100 miles to have a consistent weak, groundwave signal, but that was 
while I was playing around while mobile using vertical antennas.


  Do you know what KG-84 ciphered message traffic looks & sounds 
like?    If it's a US/NATO secure broadcast, it should be KG-84 or
possibly KY-100/ANDVT, but the latter would sound much different than 
what you're describing.


  If it is interfering with HF amateur communications you could contact 
the FCC's National Watch Officer or do the ARRL Official
Observer/Intruder Watch route, and or see if K6LY, the Naval 
Postgraduate School ARC & N6IJ, the Marina Amateur Radio Association
which operates the former Fort Ord MARS station can provide some bearings.


  Tim
Strategic HF Comms site/systems history buff & SIGINT'er
San Francisco Bay area

Geoff Fors wrote:
> I am a bit behind on replying to some of the messages about this topic.
>
> I'm about 150 miles up the coast from Vandenburg AFB, in Monterey. Unless
> the signal is
> extremely high power I don't think it would make it up here.  The consensus
> among the locals is that the signal is from the north of us, i.e. San
> Francisco Bay area, which encompasses a lot of terrain including quite a few
> military installations.  I am working on getting reports from up in that
> area to see if the signal can be heard there.
>
> I agree that upon further listening this signal is technically not Baudot
> RTTY but actually FSK data with a narrow shift.  I will hook up the DES
> M-7000 and see if I can
> determine the baud rate and shift.
>
> I checked lower frequencies (i.e. divide by 2, 3, etc.) to see if this was a
> harmonic, but they are all clear.
>
> In my case, I determined the frequency by the lazy and simple method of just
> tuning for zero beat.  For all intents and purposes 29.684 is accurate
> enough to say where it is.  The receiver is an R-1051B/URR slaved to a
> URQ-10 frequency standard.
>
> Regarding Peter's comment, you are right, there isn't much to copy on HF as
> far as commercial RTTY these days, other than something like the French
> South Pacific naval station FUF's marker broadcast (which switches to
> encrypted when they actually send something.)  I tried to read some Russian
> shipping RTTY using third-shift Cyrillic decoding but that ended in
> frustration as well.  There's always the new weekend KSM RTTY broadcasts
> brought to us by the brave folks at Radiomarine.org.
>
> Geoff
> WB6NVH
>
>
>
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