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SUNSAT Digital Messaging



This morning I captured my first SUNSAT packets on my TM-D700 while mobile
to work.   I copied the telemetry beacons, the STATUS and one Bulletin
from another APRS user, K3FOR.  In APRS Digipeat mode, the satellite only
transmits in short bursts every 5 or 10 seconds depending on how much it
has to downlink.  If you are not familiar with what 9600 baud sounds like,
it just sounds like a white noise burst.  You will see it on your S-meter.

And if it contains APRS packets, then the radio will capture them to the
front panel and to the STATION and MESSAGE lists.  To see how to set up
your TM-D700 and/or new TH-D7(G) for 9600 baud APRS, see the details on:

http://web.usna.navy.mil/~bruninga/astars.html

We will try to keep that page current as we learn the best way to operate
this new APRS Satellite mode!

de WB4APR, Bob
-----------------------------------------------

On Mon, 22 May 2000, Bob Bruninga wrote:

> This weekend, coincident with the Dayton Hamvention 2000, ushered in a new
> milestone in personal wireless  world wide amateur satellite message
> communications.  Following several months of on-air testing, and the
> convergence of several new announcements, mobile-to-mobile and handheld
> amateur satellite message communications are now a reality!
>  
> At Dayton, Kenwood revealed the 9600 baud upgrade to their existing
> 1200 baud APRS handheld,  Alinco revealed their new 1200/9600 baud data
> radio, and the South African SUNSAT team announced the availability of
> their satellite for APRS type UI messaging when not in use for scheduled
> voice passes.
>  
> Using the built in 9600 baud TNC's in the Kenwood and ALinco  data radios
> and the effecient APRS messaging protocol, it is  possbile for simple
> mobile or even handheld stations with  simple antennas to communicate
> briefly via SUNSAT or any satellite  that is enabled for UI digipeating.
>  
> ALthough the recent growth in FM voice satelites has sparked
> excitement throughout a new generation of satellite enthusiasts,
> the short, single channel voice operations are highly competitive
> and difficult to share equitably among a large number of users.
>  
> But with one-line APRS messaging, each packet taking less  than a second,
> there is potential for far more stations to share the satellite during
> each pass while also getting short but meaningful communications through
> the bird.
>                                                        
> In addition, being in digital form, any station receiving these packets
> can link them into the worldwide APRServe internet system for
> real-time delivery back to terrestrial RF anywhere on the planet.
>  
> The following example says it all.  During the Dayton Hamvention Sunday
> morning SUNSAT pass, I was trying to demo 9600 baud handheld reception 
> in the fleamarket area using nothing but my HT and whip antenna.  Hearing
> nothing but 60-over S9 interemod, I gave up and put the HT in my pants
> pocket and continued my shopping.  A few minutes later I heard the
> tale-tale beep from my HT indicating a new message.
> 
> Thinking it was just another message from my buddies at the
> hamfest, I casually pulled it from my pocket and was surprised
> to see that it was a BULLETIN from SUNSAT!  It was one of the handful 
> of Bulletins that SUNSAT downlinks and it was announcing that this
> capability was now open for general use.  There could not have been
> a better and more fulfilling conclusion to our previous testing than this
> serendipitous reception.
>                                     
> Thus, an Amateur Satellite Message was delivered to a non-optimized
> in-attentive handheld user using EXISTING amateur radio equipment.  What
> makes this possible is the 6 dB stronger downlink transmitter and 9 dB
> better 2 meter path loss  compared to the other 9600 baud UHF downlink
> PACSATS.
>  
> Although it might appear that the return path on UHF from the HT 
> back to the satellite would be impossilbe due to the additional 9 dB
> path loss, the presumption is that an HT user with an outgoing
> message would be aware of the pass and would use a handheld
> beam to make up for the difference.  Thus, we have worldwide amateur
> satellite HT message capability anywhere.  (Note, due to the real
> time digipeating of these messages, there must be groundstation
> somewhere within the same satellite footprint, about 2000 miles
> to send/capture these packets.)
> 
> But even without beams on the uplink OR downlink, we can still do two-way
> messaging to handhelds.... Here's how...
> 
> Some other non-published testing via a 9600 baud satellite has
> taken advantage of the 9dB 2 meter uplink advantage and has demonstrated
> reliable UPLINK of packets from HT's with omni whip antennas and
> non-tracking, un-attentive style message delivery.  THus, if one of the
> existing mode J PACSATS were enabled for UI APRS style messaging, then the
> combined two bird constellation of SUNSAT making message delivery and the
> PACSAT relaying return traffic, gives us a worldwide two way shirt-pocket
> amateur satellite messaging capability!
>  
> The real excitement is that we are doing this now, today.  It requires 
> NO new satellites and NO software mods to the existing birds.  Two way
> messaging is possible HT-to-HT and mobile-to-mobile.  Further enhancements
> linking this in to the terrestrial APRS worldwide internet linked
> infrastructure that then gives global real-time  delievery is simply a
> matter of adding simple omni antenna receivers at a few of the existing
> APRS IGates and a little software.
>  
> For details of this exciting new mobile satellite capability and the
> years of UI digipeating testing leading up to it, see:
> 
> http://web.usna.navy.mil/~bruninga/astars.html
> 
> We expect this site to change rapidly as more experimentation is conducted
> on this mode of communications.  SO check back in a week or so when we
> condense all this new info...
> 
> We hope this realtime-messaging capability will provide a  new lifeline
> for amateur stations on-the-go,  in the wilderness, at sea and anywhere
> else that is beyond the reach of terrestrial amateur communications.
> 
> de WB4APR, Bob Bruninga
> 
> Satellite Ground Station, US Naval Academy,  Annapolis, MD
> 
> 
> 

APRSdos REPLY/COMMENT:

Reply mail addr:   wb4apr@amsat.org   
US mail address:   115 old Farm Ct, Glen Burnie, MD 21060
See DAYTON97 HISTORY:    http://web.usna.navy.mil/~bruninga/dayton.html
See Maryland APRS LIVE:  http://web.usna.navy.mil/~bruninga/aprs.html
See GPS on ANY radio:    http://www.tapr.org/tapr/html/mic-e.html


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