[Xastir] New user..and thanks..

[Curt Mills]

On Sun, 19 Nov 2006, James Ewen wrote:

> Just to clarify for everyone, you are not tracking race cars, but the
> emergency support vehicles.

> If you set up SmartBeaconing to update rapidly when the vehicles are
> responding, you would be able to keep the dormant response vehilce out of
> your way on RF because they are not sending position reports.
> 
> Because SmartBeaconing is activated by movement input, there is no way to
> avoid collisions. You will want to use the shortest possible packets, and
> you will want the highest possible precision as well. The 60 foot grid
> precision won't cut it, you'll need the 2 to 3 foot precision.

Ok, now I see what's going on.  My recommendation (with whatever
weight that carries) would be to go with OpenTracker-1's set up for
SmartBeaconing(tm) and Base-91 compression.  Basically agreeing
wholeheartedly with what James said.

9600-baud transmissions don't buy you that much BTW because the
packets are so short anyway that the TXD takes up much of your time
in any case.  TXD is the time after the push-to-talk (PTT) line is
activated before the real part of the packet is sent.  Whether
you're using 9600 or 1200 baud transmissions, the TXD has to be
about the same.  It depends on how long the transmitter takes to get
stable/come up to full power, and on how long it takes to send a few
flag or 00 bytes to get the receive end sync'ed up and ready to
receive the real data.

Besides that, you can send 1200-baud data directly into the MIC
input/receive it as the speaker out jack, whereas 9600 requires you
to tap into the radio itself, or else to buy radios that are
"9600-baud ready".  That last is not always guaranteed either and
some of those are not all that good for 9600-baud.  Stick with 1200
baud.

The bit about the dormant vehicles not adding to the traffic is
correct if you're using SmartBeacong(tm).  A wonderful way to go for
your application.  You can set them up to not transmit at all if
they're not moving, or just transmit at a slower fixed-timing rate.
For the OpenTrackers you can also have them change their symbol when
parked if you want.

-- 
Curt, WE7U.				archer at eskimo dot com
http://www.eskimo.com/~archer
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