[amsat-bb] GO-32 Mobile Receive Success!
bruninga at usna.edu
Mon Oct 8 20:25:24 PDT 2007
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...
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