Satellite Systems: Reception
by Black Axe 
as appeared in Phone Punx Magazine Issue Two
http://fly.to/ppn



        Ever look up at the sky, and wonder what's up there?  Ever watch someone's 
satellite TV and wonder, "gee, maybe if I turned the dial and swung the dish around 
a bit, I could see what else is up there.."? Hopefully, this article can help inform 
the reader about the most common and easily intercepted forms of satellite communication.

        Before we begin, there are a few important concepts, that we must cover. If you know
anything about satellites, this part should bore you.  All satellites orbit the earth.  
Some of those satellites orbiting the earth are put into such an orbit that they appear
motionless to an earth-based station; in layman's terms, they don't go anywhere. These 
types of satellites are referred to as geosynchronous. Other satellites will orbit the 
earth.  Because they move in perspective to the earth-based observer, that observer must 
keep track of where exactly the satellite is at any given time (usually for purposes of 
antenna calibration). Keplerian Elements, readily available for most (non-spy) satellites, 
can be entered into a variety of different freeware, shareware, and commercial programs to
track the satellites. Some programs can even orient your antennas or dishes for you, to 
get the best possible signal as the satellite moves across the horizon. 

      These topics having been covered, let us delve deeper into what our dishes 
and antennas can fish out of the cosmos.

-Amateur Radio Satellites

        One of the easiest types of signals to receive from space is from amateur (Ham) 
satellites. Most amateur satellites use uplinks and downlinks in the VHF and UHF bands, 
making antenna requirements easy to fulfill.  Most of the time, a properly oriented 
telescoping whip is all that is needed. Operating modes vary; CW (Morse code) is often 
used. Other operating modes include SSB (Single Sideband), various digital modes, and FM 
voice (specifically, the AO-29 satellite). The interesting part about amateur satellites is
that not only does one have the ability to listen in, but also the ability to use these
satellites for their own communications. Some digital 
satellites even house entire BBS systems.


-MIR and SAREX

        One can also communicate with the Russian space station, MIR, and 
(at certain times) the American Space Shuttle (SAREX). Cosmonauts aboard the space 
station MIR operate voice and a packet (digital) system onboard in the 144-mHz 
amateur band. The American Space Shuttle's SAREX (Space Amateur Radio Experiment) 
is a more clandestine operation, consisting of a handheld radio and a window-mounted 
antenna. FM voice is used on a number of different frequencies in the 144mHz band. 
Amateur radio operators are EXTREMELY competitive in making a SAREX contact, usually 
just for the nice postcard (QSL) that NASA sends.


-Inmarsat

Now we delve into more of a "grey area" of satellite monitoring. The Inmarsat 
system consists of four geosynchronous satellites serving the entire surface of the 
Earth with satellite telephone service. Ridiculously expensive, Inmarsat service 
is generally only used by well-funded people and organizations. Some Inmarsat 
traffic is digital.  However, there is still an abundance of voice traffic to be 
intercepted. Transmission mode is companded FM, meaning that signal strength 
varies with the noise level (used to conserve power consumption); set your squelch 
accordingly. To intercept Inmarsat traffic, a receiver capable of covering 1500mHz 
is required, along with a dish and a directional antenna (Yagi). Orient the Yagi 
(tuned for the band) towards the dish, and affix it to the dish's LNB. Find the 
satellites in the sky (this will be left as an exercise for the reader); tune the 
receiver to 1537mHz to find a constant signal transmitted by the satellites. 
Modulation mode is Narrow FM; steps of 25kHz. Have a tape recorder ready; you never
know what you'll hear.


-TVRO
  
        TVRO stands for TeleVision Receive Only. Basically, it is what is known as 
satellite TV. Although many pay services are common nowadays, it is still possible 
to intercept a great deal of analog video traffic from TVRO satellites. Basically, 
what is required is a TV (of course), a satellite receiver, a dish with an LNB 
(Low Noise Block converter), and rotors to spin the dish around. What's out there, 
you say? Of course, there's regular network TV, and many other less-common broadcast 
services. By far, the most interesting part of TVRO is "wild feeds", that is, live 
video being transmitted from various locations to broadcast studios. For example, 
during the conflict at Waco, there were four live and uncensored feeds coming out of 
Waco, 24 hours a day. You'll get to see all the blood and guts that are edited out
of the network broadcast, along with reporters you'll recognize very well bitching 
before a broadcast, smoking a quick cigarette, etc.  The world of TVRO is vast 
and ready for exploration. 



