Friday, November 27, 2015

Something new in APRS land #ARRL #hamradio

The next Ham DTMF satellite is on the air for testing in Annapolis.

Anyone can use this transponder from their DTMF radio. (don’t need an APRS radio).  Just enter your DTMF callsign and GRID into a DTMF memory (formatted per the web page below) and send it on the 144.33 uplink and listen for the voice response on 144.39 (amongst all the packet clutter too).

Not only does it convert the DTMF to a voice CQ, but it also sends back an APRS packet copy of the CQ on 144.39  into the global APRS system.  If successful, you should see it in the ten minute Bulletin update:

So just program your DTMF memory once, and try it any time you drive by Annapolis (its on my building roof at USNA). 

And not only can you send your grid, you can send any of the ARL radiograms both emergency and general, but any of a few dozen more typical messages just by entering the 2 digit message number in DTMF followed by your DTMF callsign….


We just delivered the flight unit to the launch integrator 18 Nov, and so now we can sit back and actually TEST the prototype on the air and see how it works under user load.  It is only 4 Watts, so you probably have to be within a few miles or so.  Something to entertaiin you while sitting in traffic.    I have worked it from a high spot in Glen Burnie (bridge over Rt 10) about 12 miles away, but you have to have a good shot to Annapolis.

You only have to enter your grid and call into your DTMF memory once.  Then, anytime you are mobile near the Severn bridges or near the Academy, just send out the DTMF memory and listen for the response.

If there are thunderstorms in the area, I should disconnect it… but will try to leave it on.

 -----------Now the new idea! --------------
But here is the NEW idea of how to use its 2 digit message capability locally...

1) Have it listen from a very high central metro area location for DTMF on 146.58

2) The two-digit messages (01 to 99) can be used to trigger the APRS and voice response of "CALLSIGN, LISTENING ON XXX.XXX MHz"

3) then ALL APRS mobiles in the area will see the message on their radios
4) AND he messages goes worldwide in the APRS-IS system
5) You could be called back via Echolink for example
6) AND if anyone is monitoring 146.58, they will hear EVERYONE on the air and where they are listening.

In our area with over 50 repeaters, we are so spread out, hardly any repeater is being used.  But this way, everyone's "presence" on the air is announced on APRS and the single 146.58 just like APRS was always intended to be... a single clearing house channel for everything happening in ham radio.

But now you only need a DTMF radio.  Not a full APRS rig.

Oh, we just make a local list 01 to 99 of the different frequencies.  Every local list is different, but so are the repeaters in every local area...  Though I am starting to think it can be quite universal!  Wow, Il start now... for example 76 is 146.76 and 94 is 146.94, etc!

You just program  your DTMF memory with the few repeaters you use, and then sending out your message is just one button.  Send the DTMF memory with your chosen "monitoring frequency!

for more info on APRStt see http://aprs.org/aprstt.html

Bob Bruninga, WB4APR
USNA Satellite Lab

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