[OZAPRS] GO-32 enabled for experimental APRS access

Richard Hoskin vk3jfk at amsat.org
Sun Sep 23 10:54:05 EST 2007


FYI.

 

Note; I will try to get a GO-32 SGate/IGate up and running in a few weeks
time if anyone is interested in using this Satellite.

 

Cheers

Richard

VK3JFK

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GO-32 enabled for experimental APRS access

 

AMSAT News Service Bulletin 266.03

 From AMSAT HQ SILVER SPRING, MD.

September 23, 2007

To All RADIO AMATEURS

BID: $ANS-266.03

 

The GO-32 Satellite TECHSAT-1B team has announced experimental 9600 baud
APRS access for mobile and tactical APRS on a not-to-interfere basis

with the existing PACSAT BBS.   

 

The uplink is possible with 5 Watts on 2 meters, but the downlink is 9 dB
worse to an omni antenna on UHF and requires tuning 10 to 20 KHz for
Doppler.  Currently there are no permanent IGates to bring the downlink
into
the global APRS system, but it is hoped volunteers will surface with
permanent satgates.  So initially, do NOT expect to see yourself on
FINDU.COM.  Enjoy ham radio,  Make a contact instead!

 

Experimental testing shows that an APRS HT with a 19.5" whip can get a
lucky
shot into this satellite (but not when there is congestion on the uplink).
With a handheld beam, it should be no problem for an HT, and the beam is
needed on reception anyway.  Fifty Watt mobiles should have no problem
using
a stock mobile whip.  Due to the absence of APRS signals to date, we do
not
have good statistics on reception in a mobile yet...

 

Operating on a 9600 baud FULL DUPLEX APRS satellite is MUCH different than
ARISS, or any of the other 1200 baud APRS PCSATS. Because the turn-around
is
so fast, you cannot see your own digipeated packets on the same radio
(usually)...  Please read and understand this entire bulletin before
attempting to operate.

 

The easiest way to get on GO-32 with 9600 baud APRS is to use a Kenwood
D7,
D700 or D710 radio.  These radios since 1998 have been satellite 9600 baud
ready, just waiting on a satellite!.

 

Read these notes on how to operate GO-32 with a D7 or D700:

 

Set APRS Baudrate to 9600 baud.  

Set A band to uplink on 145.93

Set B band to receive 435.225 +/- 10 KHz Set Path to be via 4XTECH Set
MYCALL to a unique SSID Set TX method to AUTO Set TX RATE 1 min for HT. 2
min for D700 Put something useful in your STATUS text maybe describing
your
setup:

"50W mobile, 1/4 wave, 2m rate" or "5W HT, long whip, 1m rate"

 

Save in a PM for use anytime you are outside of the terrestrial APRS
network.

 

SATELLITE OPERATING NOTES:

 

The GO32 uplinks and downlinks are for the PACSAT store and forward system
and users.  APRS use is on a secondary basis and should not be operated
unattended.  If you see that the BBS PBLIST is full of other users, do not
enable your APRS since the uplink will be busy.  Currently the PBLIST is
not
in APRS format so you cannot see it unless you are running normal packet
mode.

 

On the D700 you can press PMON on the front panel and see these packets...
but they FLY by...

 

ACCESS TIMES:  GO-32 is sun synchronous and so it comes over everywhere
three times between about 8 AM to Noon and again between 8 PM to midnight
local sun time.  During these two windows at least one pass each will be
an
overhead pass which might also work for an HT.  The other passes will be
lower to the East or West and will work fine for a 50W mobile.

 

WHAT YOU HEAR:  9600 baud sounds almost exactly like open squelch, though
the tuned ear can soon distinguish the difference.  Before the pass, set
your squelch normally to quiet the speaker.  When you hear the satellite,
the squelch will open and you may see up to 3 bars on your S meter.  Tune
to
the "best sounding" noise.

 

DOPPLER:  Depending on how low to the horizon you can see, the satelite
approaches 10 KHz high at 435.235 MHz... But it is maybe 3000 km away.

As it gets higher, and 6 dB closer, it will be on 435.230 MHz, passing
through 435.225 published center frequency at the middle point, and then
drop down through 435.220 and ending at 435.215.

 

But since it is 6 to 10 dB closer (and stronger) towards the center of the
pass (800 km overhead), the mobile antenna is probably only going to hear
the middle 435.230, .225, .220 portion easily.  So I would start my
receiption at 435.230...

 

UPLINK CHANNELS:  GO-32 allows two APRS uplinks.  One is exclusive to
D7/D700 tactical position reporting and the other exclusive to messaging.
This is in hardware, not policy...

 

1) All APRS messaging (or fixed station non-Mic-E positions) must use the
145.85 uplink where GO32 only digipeats APRS packets with TOCALLs that
begin
with the usual "APxxxx".  (Even the D7 and D700 use "APKxxx"

for messages.)

 

2) All APRS Mic-E position uplinks (D7, D700 and D710s) must be on

145.93 MHz and they must have the position comment set to "Committed,
Special or PRIORITY"...  With those comment settings then the TOCALL first
LATITUDE digit will be 1,2,3,4,5,6,7 and only these will be accepted by
GO32
for digipeating from 145.93.

 

DATA CARRIER DETECT: The D700 and non(g) model D7's will NOT TX if they
are
hearing the downlink at the same time due to CARRIER DETECT.  The

D7(g) model has DCD IGNORE that *will* let it TX anyway.  So use separate
rigs for TX and for RX if you want to see yourself.

 

Otherwise stick to the receommended TX rates and know that you are getting
in if you stick to the protocol.  Sticking to the recommended rates also
keeps channel loading low, so that everyone gets in with less congestion.

 

PERMANENT SATGATES:  Here is a great place to use your D7 HT when you are
not using it otherwise.  Simply connect it to a 19" whip over a ground
plane
and to your APRS IGate system.  The antenna does not even need to be high,
since it cannot hear, nor will it be on frequency for low packets near the
horizon 3000 km away.  Set it to 9600 baud RX and tune to 435.230 (which
is
5 KHz high).  This Doppler setting will match the stronger signals.

 

This 19.5" whip (3/4 wave on 435) does not need to see below 25 degrees,
since its max gain (almost 7 dB) is between 30 to 70 degrees anwyay.

This also protects your HT from lightning, since it can be low, below all
of
your other antnenas.  Yes, your station will only see about 30% of all
possible packets and only on the best two passes per day, but combined
with
dozens of other such unattended SATgates, all packets should be heard
somewhere by someone and injected into the APRS Internet system.

 

Bob Bruinga, WB4APR, reports that he hopes to have an APRS-via-GO32 web
page
up in a few weeks.

 

Additional information about GO-32 can be found on the AMSAT web site

at:

http://www.amsat.org/amsat-new/satellites/satInfo.php?satID=14
<http://www.amsat.org/amsat-new/satellites/satInfo.php?satID=14&retURL=/sa
te
llites/status.php> &retURL=/satellites/status.php

 

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