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[aprssig] GO-32 Mobile Receive Success!

Robert Bruninga bruninga at usna.edu
Thu Oct 11 11:52:50 UTC 2007


> Tonight I finally remembered to set my D700 in 
> my van to the 435.225 GO32 downlink.... I was 
> not disappointed.  Received over 150 packets 
> during the central 6 minutes of the pass. 

I have now plotted that data on the APRS GO-32 page:

http://www.ew.usna.edu/~bruninga/GO32-ops.html

It clearly shows that the mobile link works at elevations above
about 25 degrees and a quick look at GO32 passes reveals that
they occur every day within an hour or so of 10 AM and 9 PM
local DST time.  (Your times may vary +/- 30 minutes from that
depending on where you live relative to the center of your time
zone.

Bob, WB4APR

> I was just making hash marks 
> on the back of an envelope while watching the packets fly by 
> on the front panel of the radio.  I did tune 3 times for 
> Doppler since I was just sitting there with nothing else to
do.
> 
> This confirms that an unattended D700 or D7 hooked to a 
> simple OMNI antnena (and short coax) can make an excellent 
> APRS satellite gateway.  With say a dozen of these across the 
> USA, then the APRS-Internet system should get a solid
downlink!
> 
> After the fact, I came in and looked at the pass on 
> Instantrack.  Here is the nitty-gritty showing the elevation 
> angle versus number of packets received per minute.
> 
> TIME  EL  PACKETS
> 0933  30  18
> 0934  40  23
> 0935  46  36
> 0936  45  35
> 0937  36  24
> 0938  26  13
> 
> For an unattended ground station without Doppler tuning, my 
> guess would be that this station would have received the 
> center full 3 minutes of this 45 degree pass.
> 
> So, what is your handy D7 doing sitting on your shelf turned 
> off?  Hook it to a 19" vertical whip over a ground plane 
> outside your window  and contribute to the National GO-32 
> APRS downlink system!
> 
> Ill get someone to write a simple turn-key APRS IGate 
> background application, so you don't have to hasssle with all 
> the other APRS stuff if you dont want to.  This way, you can 
> just turn on the D7, hook it to a serial port, run this 
> application in the background, and you too will be a 
> contributor to the solid APRS downlink from GO-32!
> 
> Oh, On the D700, I had pressed the PACKET MONITOR button so 
> that I was seeing all GO-32 downlink packets on the front 
> panel, not just the APRS ones.  The D7 does not have the PMON 
> button, so you will only see the APRS packets.  But I did 
> receive the 3 APRS downlink bulletins perfectly many times, 
> and every 30 seconds or so, I did receive the GO-32 TIME 
> STATUS report on the front panel of the radio.
> 
> So, even if you are not going to Igate, just hook that D7 to 
> an outside 19" vertical whip (this serves as a 3/4 wave gain 
> vertical on the 435 downlink) through a short coax (Antnena 
> height does not matter, coax loss does!).  You won't hear 
> anything below 30 degrees anyway...  And just leave the HT on 
> all the time tuned to 435.230.  Every morning and every 
> evening, you will receive GO-32 and any other APRS operators 
> playing that evening. 
> 
> When you hear good signals on 435.230, then 2 minutes later, 
> switch to 435.225 and so on.  When the pass is over, set your 
> radio back to 435.230 for the next HIGH pass 12 hours or so
later.
> 
> You can leaave this on all the time, since it will not wake 
> you up.  GO-32 PEAK passes are within an hour or so of 9 AM 
> and PM local time (maybe an hour later after the change back 
> to standard time)..
> 
> Thousands of AMSAT folks have these D7's, and I bet that 99% 
> of them are not in use most of the time.  All we need are a 
> dozen or so serving this space-diversity ground station
function...
> 
> Thanks!
> 
> Bob, Wb4APR
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