[amsat-bb] Re: Tracking Friends at Dayton..

Robert Bruninga bruninga at usna.edu
Thu May 14 07:00:00 PDT 2009

>> This year you can use your DTMF HT to report 
>> where you are hanging out at the Hamvention 
>> to about 120 feet just by sending
>> two digits for your XY coordinate.

> LOL...  
> If I were going... I'm going to say via that same HT... 
> "I'm standing in front of the Brautwurst stand." 
> Faster than looking myself up on an arbitrary map, 
> punching digits, hoping my friend has the map... 

APRS was never intended as an end in itself.  It is just another
tool in the Ham's toolbox.  And it is NOT a tracking system.  It
was never designed to provide the bandwidth for continuous
tracks on everyone or even on ANYone.   That is the great
missconception about APRS and what burdens the network with
unnecessary tracking data when 99% of everyone could care less
where 99% of everyone else is.

APRS is a communications system on a single National channel
everywhere to facilitate communications between hams needing to
communicate without apriori knowledge.  There is no reason to
transmit your position, unless there is a specific reason why
you want someone else to know where you are at that instant.  Or
to give them in the blind, your call-back frequency.

At Dayton, if you stop for an hour in a forum, or stop for 30
minutes under your club tent, or at the food court or the Bar,
then you might want to send out a posit to let your buddies know
where you are.  In this case there are only four XY coordinates
of interest to you.  The one at your club tent, the one at the
food court, the one at the bar, and the one at the Forums.

> Alternatively, someone who wants to know 
> where I am can call my callsign on an 
> agreed frequency.  

That works too but requires some inconveniences too. 

1) you must have a pre-arranged freq
2) the freq must be relatively clear of other chatter
3) No opportunity for meeting others without #1,#2
4) the recepient must be listeing FULL time
5) Must have his volume turned up
6) Must be paying attention to ALL voice traffic so that he can
possibly hear his own call amongst the othres

So both methods have advantages and disadvantages.

An advantage of APRS and APRStt is that the system is global.
Once you send out your DTMF callsign memory, anyone in the World
of amateur radio that needs to conatact you can not only see you
are in dayton (or timbucktu), but can text message you.  Again,
not that anyone would, but if you ARE expecting someone at a
distance to contact you, this gives you the means to be

For special events like marathons, etc.  Just two single digit
numbers you may use for your position can be the mile-marks.
This lets a VIP shadow, or SAG wagon or any other non-APRS
moving asset occasionally report what station it is near (not
while moving of couse0, but when he shifs from one station to
another.  This eliminates a lot of voice traffic from an already
overloaded voice net.  There are xxyy, xxxyyy and xxxxyyyy
higher precision formats available.

Hope that helps.
Bob, WB4APR> 

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