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Easy, Easy SATGATES!



Here is how we can have EASY satgates almost overnight to support
worldwide distribution of UI digipeated packets via all of the ASTARS
satellites (see ASTARS web page):

Whenever you park your TM-D700 APRS mobile out doors, hit a PM as you
leave.  Your vehicle instantly becomes a SATGATE that is about as good as
it gets!  I had forgotted about this idea until I was updating the ASTARS
web page and then saw where I had proposed it over a year ago long before
launch of PCsat...  Here is why it works so easy:

1) The 1/4 wave roof antenna with short coax will hear WELL (high passes)
2) With many of these, who cares about the low ones, someone else gets 'em.
3) The TM-D700 does UI digipeating with call substitution
4) The digipeat is cross banded to 144.39 where it enters the normal APRS
   internet system!  (assuming an IGate is within range of your vehicle)

Thus, flip the switch when you leave your vehicle, and it just works!
Here is how to set it up in one  of your program memories (PM's):

1) Set a channel to receive the satelltie and XMIT on 144.39
2) Put "SGATE" in your APRS UIDIGI menu callsign list
3) Enable DIGIPEAT ON.
4) Put this in a PM so that you can also turn it OFF easliy too!

This works perfectly for ISS, SAREX, PCSAT, and SAPPHIRE.  Drats, it wont
work for UO-22 because the D700 cannot hear at 9600 and then digipeat at
1200.  To do this for UO-22, would need a KPC-9612 with the MYGATE
callsign set to SGATE.  THen it would crossband and cross-baud-rate repeat...

*** NOTE *** This requires all USER packets to include SGATE,WIDE in their
path such as:

 Via SPACE STATION: VIA ARISS,SGATE,WIDE
 Via PCsat:         VIA ARISS,SGATE,WIDE    (when it is loaded right)
                    VIA W3ADO-1,SGATE,WIDE  (when it is using W3ADO-1)
 Via SAPPHIRE:      VIA KE6QMD,SGATE,WIDE

In general, adding SGATE,WIDE as a final hop is not a bad idea in all
cases for anyone wanting to get into the internet to allow for just these
kinds of one-hop forwarding of Space digipeated  packets.  I use this
technique frequently at indoor demos to digipeat  satellite packets from
my car in the parking lot to indoor displays...  But it does add 14 bytes
of overhead to every packet... But if you want your packet to get to the
inernet, it is good insurence...

My excitement in this post was because the D700 can do 9600 baud and so
this was the trivial way to get SATGATES listening to UO-22 on the air...
but I had overlooked the fact that it must digipeat to 144.39 at 1200
baud to close the loop to the internet.  Since the D700 cannot do this,
then the only other EASY way is the "umbilical" idea where you leave an
RS-232 cable in your driveway and plug your D700 listening at 9600 baud
to UO22 into your indoor APRS IGate system every night... argh...

Oh yes, also, the best antenna is a 19.25" whip on your vehicle roof to
get good gain overhead.  Few people run these basic antennas, but run
5/8th or other gain antennas.  These put the gain on the horizon where it
is useless most times for mobile satellite work...  ALso, the 19.25" whip
antenna in the center of your roof has great overhead pattern and gain for
both 2m and UHF!  SO it is great for UO-22 as well as the 2m birds...

WB4APR@amsat.org, Bob

PCsat WEB  page     http://www.ew.usna.edu/~bruninga/pcsat.html
ISS-APRS FAQ:       http://www.ew.usna.edu/~bruninga/iss-faq.html
CUBESAT Designs     http://www.ew.usna.edu/~bruninga/cubesat.html
APRS LIVE pages     http://www.ew.usna.edu/~bruninga/aprs.html
APRS SATELLITES     http://www.ew.usna.edu/~bruninga/astars.html
MIM/Mic-E/Mic-Lite  http://www.toad.net/~wclement/bruninga/mic-lite.html

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