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[aprssig] A/N Footbal Run is underway!

Robert Bruninga bruninga at usna.edu
Fri Dec 5 22:10:18 UTC 2008

>> This year, they wanted to try changing 
>> callsigns on the fly (which I am sure 
>> will lead to problems!)....
> This would be SOOOO much easier with the 
> tactical call on the fly stuff that APRS+SA 
> and Xastir has. 

This is a long debate on APRS.  Curt is absolutely right for
closed events with a few central displays of a lot of
one-way-trackers.  No question about it.

On the other hand for broad-based general events involving
dozens of two-way APRS distributed information display systems
throught a broad event, it is a recipie for disaster.  We are
both right, of course, it just depends on one's situation and
event.  SO here is the flip side for the broad event:

The statement is True... IIIFFF everyone at an event or
associated with the event exclusively used one of those clients.
Last time I checked, they accounted for about 4% of all APRS

As most everyone has heard me pontificate the opposing view, I
strongly oppose reliance on display and swapping of callsigns on
RECEIPT for broad general applications for many many reasons:

1) It leaves out 95% of all users

2) It leaves out 100% of all mobiles with APRS radios

3) It guarantees that voice nets will have to talk APPLES and
ORANGES for the same assets because different clients will see
different callsigns for the same things.

3) Even if 20 years from now we get 90% of a club to use those
exclusive clinets, then still the last thing one would every
artificially introduce at a comms event is the potential for
even 10% of the communicators to be seeing not the same thing
that everyone else is seeing.

Further, even those with the correct software will see the
*wrong* callsign until they get updated, and sometimes the only
posit on a station is one-in-a-hundred, so even then too, you
may have half the people seeing the wrong thing for a long time
until the tactical-change-call-packet gets through on RF.

As a comms planner, the last thing I would ever encourage is
anything that tries to change callsigns on the fly on receipt
(again, for a broad based involve everyone two-way tactical
comms event).

The ONLY guaranteed way in APRS to assure that everyone is
seeing the same thing is to change the callsign at the source.
Done.  No ambigity, no cross reference, no missed signals, etc.

This is not to say that some events that exclusively use those
special clients should not do so, but in my mind, with 95% of my
surrounding volunteers showing up with something else, it seems
counter productive to full participation.

Changing calls on receipt in a few clients seems to me just a
receipe for comms confusion... The last thing that ham radio
needs to bring to an event. 

Again, I am not denegrating that approach for closed-special
events, but, In my mind, the solution is for all hardware
devices with callsigns should be encouraged to make it trivial
for FIELD-UPDATE with no tools, PC, or devices involved.  That
is the only reliable, non ambiguous method for changing tactical
calls during an event.  That's why we like the PM's in the
D700's, because the mobile can change the call on the fly, and
it instantly propogates to everyone of every kind throughout the
RF and WEB domain.  That is where the emphasis should be made...
Improved callsign changing in the devices.

Lets encourage the TRACKER MFR's to provide a button if nothing
else.  THen key the new call into the device in CW!  Or two
buttons for scroll/select... Anything to change the call in the
field with no tools required.

> [with XASTIR or APRS+SA]...
> The trackers themselves don't need to 
> change a thing.  Anybody can send out the
> message, but only those software packages 
> capable of parsing the message and updating 
> the tactical calls will see it.

But as you say, eveyrone else sees a totally different callsign,
and so you have people on the voice nets talking APPLES and
ORANGES, a sure receipe for disaster for a broad based event.

> Sure would be nice if all the APRS programs had that feature!

I agree, but in reality, it is a nice dream in a closed
universe.  But the better dream is for Hardware APRS devices to
have a button for field-setting-the call.  Works every time, and
100% of everyone that gets the packet will know exactly what and
who it is, with no latencey, ambiguity, or delivery errors.

> We've been using this in public service 
> events to eliminate changes to SAG 
> vehicle trackers and the like.  Now we 
> leave the APRS mobiles/portables totally 
> alone that show up to help, thereby
> increasing the chances that they'll be 
> seen on the map.

I agree at closed events, with nothing but a few XASTIR or
APRS+SA special displays at a few VIP locations.  I Agree..
BUT, the goal of the distributed APRS system at many events is
to give the tactical picture to all comms operators, at their
operating position...  And unless everyone uses exclusive
software, then the callsign-swap-on-receipt creates more
problems than solved.

Everyone note.  We are BOTH right.  It just depends on the type
of event.  If the event is of the specialized "one-way tracker
type" then of course the XASTIR/APRS+SA system works best with
just a few displays.

If the event is broad reaching of the two-way comms with
everyone seeing the same picture, then I still think changing
the calls at the source is the only workable solution to
eliminate comms confusion.

> We've had MUCH lower success
> rates with trackers that are configured 
> just before or during an event, or 
> tracking packages that are brought out 
> of mothballs and set up just for the 
> event (estimate 50%).

AMEN!  We agree completely.  So lets fix that configuration

> We update tactical calls at the mapping stations involved in
> event, and can update all of the mapping stations at once from
> one station.  Any station in the area with the same capability
> hears/decodes the messages will also see the tactical
> Consider adding this feature to the spec addendums?

It's a great feature, but missuse causes far more problems when
it is used improperly.  And the experience over the many years,
is that a large number of APRS operators are not keeping current
and so such a featue would almost guarantee to create more
problems than it solves.

I'd rather use that energy to focus on better field-changeablity
of callsigns in APRS mobiles.  We have that with the D7, D700,
D710, VX-8R, HAMHUD.  All we need is new devices to consider
this issue and fix it.

By the way, the ISS FM voice repeater is working now, and I hear
QSO's as I type.  You can hit it with any FM mobile.  Once
eveyrone figures it out, it will be impossible due to
Just my 2 cents.

> -- 
> 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

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