[OZAPRS] Ultimate3 HF APRS tracker

Hans Summers hans.summers at gmail.com
Mon Oct 20 19:56:04 EST 2014

Hi all,

I am designer of the Ultimate3 (a.k.a. U3), an inexpensive QRSS/WSPR
transmitter kit (see http://www.hanssummers.com/ultimate3 ) available from
QRP Labs http://www.qrp-labs.com . The kit has a transmitter and GPS
interface, and can send various QRSS modes, Hell, and WSPR. In the
forthcoming v3.06 firmware I've also added Opera and Pi4 modes.

The kit can do FSK and has precise frequency control using DDS. 300 baud HF
packet with 200 Hz spacing would be no problem. It has GPS an the
transmitter. So it seems theoretically, I should be able to add APRS
tracker capability without too much trouble.

I understand HF APRS is popular in Australia because the large distances
involved mean gaps in 2m coverage. So I thought this would be a good place
to ask. Two questions, if I may:

Question 1: despite a lot of reading on APRS I haven't figured out what
simple message would need to be sent for a tracker. It should presumably be
some text where the callsign and latitude/longitude get inserted. Can
anyone advise? What simple message needs to be sent? And any other things
to consider?

Question 2: once I have a beta firmware version available, is there anyone
here who has a U3, and AVR programming facilities, and could actually beta
test APRS in the field (which I cannot easily manage). Even if not... If
someone is seriously able to test and work with me on this then I can
consider donating a free U3 kit for the project.

Another comment - I'm working on getting the U3 operational on 2m soon as
well. See http://www.hanssummers.com/ocxosynth which will soon be available
as a kit too, and hopefully will get the U3 up on 2m.

Thanks in advance, and apologies for the bandwidth

73 Hans G0UPL
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