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[aprssig] GO-32 Mobile Receive Success!

Robert Bruninga bruninga at usna.edu
Tue Oct 9 13:20:38 UTC 2007


> A few weeks ago, I listened with my D7 ..., 
> but couldn't decode any packets.  I checked 
> all the settings twice.  

There is only 1 setting to receive.  That is,
MENU-APRS-PACKET-SPEED-9600

But you should only expect to see packets on the one highest
elevation per night or morning.  Only during the central 3 to 5
minutes is the satellite close enough to receive on an omni.
Using a 19" whip helps by a good 3dB.
Because 19.5" is a 3/4 wave vertical on UHF and has almost 7 dBi
gain.

> I should be repairing a 1/4 wave vertical on my roof in a few 
> weeks. 

For receiving GO-32 on an omni, short coax run is a MUST.
Anything over 15 feet or so and you may lose too much signal..
So a simple antenna out the window that can see UP above 30 deg
is all you need.  No need to be higher if it means more coax..

Bob, WB4APR

> ---- Bob Bruninga  <bruninga at usna.edu> wrote: 
> > Received over 150 packets from GO32 in the mobile!
> > 
> > If you want to impress someone with handheld Satellite 
> Communcications, just stand outside during the prime morning 
> or evening pass of GO-32 with your D7 HT set for APRS 9600 
> baud receive on 435.230 (5 KHz high at the start of the pass) 
> and watch the messages fly by... Switch to .225 and finally 
> to .220 by the end for maximum packets.
> > 
> > Tonight I finally remembered to set my D700 in my van to 
> the GO32 downlink.  Was out doing honeydoos around 7:50 PM 
> and heard a few squelch breaks.  This would be the first 
> evening pass.  So that told me to be out 100 minutes later 
> for the prime pass of the evening.
> > 
> > I was not disappointed!  Received over 150 packes during 
> the central 6 minutes of the pass.  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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> 
> --
> -Al Gerheim
> 
> HP-49G+ Software Page:
> http://members.cox.net/above
> 
> 





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