[amsat-bb] Re: GO-32 APRS experiments Tuesday

[Robert Bruninga]

>> This morning at 9 and 1030 AM EDT passes over 
>> the East Coast USA, we hope to do a student
>> demonstration of APRS packets via GO-32.
>
> If you have a D700 with built-in 9600 baud TNC, 
> then set your mobile for these parameters while 
> your car sits in the parking this morning.  
> 
> Set APRS Baudrate to 9600 baud.  
> Set A band to uplink on 145.93
> Set B band to receive 435.225
> 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 uplink is on the order of 20 dB more effective than the
> downlink.  Menaning it is easy to get in, but difficult
without
> a beam to hear it.
> 
> See my GO-32 APRS operations web page:
> http://www.ew.usna.edu/~bruninga/GO32-ops.html
> 
> ACCESS TIMES:  GO-32 is sun synchronous and so it comes over
> everywhere at USA latitudes 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 Mic-E formatted (Think 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.
> 
> The D7 can get in with a 19.5" whip during the center of the
> pass.
> 
> Here is a link to AMSAT's description of GO-32:
> 
>
http://www.amsat.org/amsat-new/satellites/satInfo.php?satID=14&r
> etURL=/satellites/status.php
> 
> Good luck!
> 
> Bob, Wb4APR
> 
> 
>