[OZAPRS] Some speculation from an innocent bystander ...

Terry Neumann tfn at rbe.net.au
Sat Jan 10 00:04:02 EST 2004

G'day HF'ers,

Recently Warren asked me to monitor his APRS mobile packets on 30 metres,
and I started to take a little more seriously  what I was seeing on the
UI-View  screen.  The first report is that unfortunately since Warren
asked me, I haven't seen anything from him so far.  Maybe propagation is
not as good as it might be.

However I watching the other mobile on the screen (Brian) I became aware
that something else was missing - namely the speed and heading information
which I had taken for granted on VHF.

So here comes the speculation:   In looking at the  <more> screen on
UI-View, I don't see any data of this type.  I'm presuming therefore that
it isn't being sent, and speculating that this is happening because of the
extra length this would add to the tx packet. 

It seems a pity since this information is often the most interesting part
of the SWL /APRS activity.  Altitude is an extra bonus when it's
available, but then that's the pilot in me ....:-)

Assuming I'm correct in the supposition above, I wonder if it really adds
all that much to the packet if the speed and heading is added to the tx
data - assuming of course that it can be.   It would certainly add much
more interest, even if it's at the expense of the vehicle information (OK,
OK  I'm jealous Brian - I'd like a Forester too ;-))   Without the speed
information as a minimum, one doesn't know the object is moving unless you
go to a fine detail map as I did tonight.   

I'm not sure  how the other trackers work, but in the KPC-3 it's possible
to send different information packets with different beacons.   This would
mean (presumably again) that one could send position on one beacon and a
'x' seconds later  another beacon packet with the speed/heading/altitude
data.  Of course the KPC-3 isn't usable on HF - it's 1200 b only, but you
get the drift.   Pure wishful thinking.

In monitoring the 30 metre propagation over the past week, the most
immediate conclusion is that VK3MY  is in the ideal  radius from my QTH.
Ross is there almost all of the time, and every packet appears to be
decoded correctly as far as I can see.  The Brisbane stations appear to
vary in strength and readability.   Pings to VK4DMI are sometimes
returned, sometimes not. And Brian's signal is not always present -
perhaps the station is not always running.

And under this puzzling business is the nagging question as to just how
crucial the matter of being on the right frequency is - especially with
the variation already highlighted about different tnc's/trackers using
different tones and shifts.   Underneath it all are occasional packets
from other stations which are not at sufficient strength to be decoded -
so far.    Not to mention occasional voice stations, other unidentified
noises from the deep, and for a couple of hours yesterday, a few bursts
from what sounded very much like the infamous Russian Woodpecker of a few
years ago.     

Fascinating stuff.....

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