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[aprssig] pointless text in the status

Curt Mills archer at eskimo.com
Thu Jun 1 02:32:39 UTC 2006


On Wed, 31 May 2006, Stan - N0YXV wrote:

> That brings up a question I've always had. How much more does each character
> add to the overall loading of APRS. In other words if I use 10 characters in
> my status text instead of 20 have I cut my packet in half? Put another
> way...if 10 characters plus all header and tail bits in a packet is half a
> second long will 20 characters be one second long? My question revolves only
> around network and network loading.

Hmmm.  I've wondered the same thing, so many years back I ran some
experiments to see what effect packet-length had on my packets
getting through.  I didn't collect statistics at the time, but just
got a good look-and-feel for it.  I started with GPGGA or GPRMC
packets, then went to APRS-formatted packets, then to Mic-E, then to
Base91 Compressed.  I had a bit of trouble with getting corrupted
Mic-E packets back then because some of the igates or TNC's were
messing up Mic-E protocol at the time.

Anyway, to make a long story short, as the packet length decreased,
the number of packets that actually got received somewhere increased
dramatically.  So much that now I usually run with no comment and
with no added parameters which might make the packet longer.

All of the other conditions were about the same, I was running a 25W
IC-27A and a mag-mount antenna on my Chevy truck, and driving about
the same commute every day.  I ran a few days to a week with each
configuration.

I now run with an OpenTracker-1 set to Base-91 compression.  I don't
have any comment set while moving, but when I'm parked it transmits
the Jeep's battery voltage in the comment field until the APO kicks
in and turns the equipment off.

-- 
Curt, WE7U.				archer at eskimo dot com
http://www.eskimo.com/~archer
  Lotto:  A tax on people who are bad at math. - unknown
Windows:  Microsoft's tax on computer illiterates. - WE7U.
The world DOES revolve around me:  I picked the coordinate system!"




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