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[aprssig] Voice Repeater Frequency Objects

Robert Bruninga bruninga at usna.edu
Thu Sep 18 16:15:54 UTC 2008


> Bob [I think] is saying: the aprs user should 
> be the final authority in formatting of the 
> comment (within the parameters of the spec.)

>> There is nothing new in the discussion

Yes, let me try a different way of explaining it...

There are inconsistent limitations in most receive systems for
the length of the comments that are displayed.  There are known
displays with these width restrictions:

128, 80, 64, 54, 43, 28, and 20 bytes.

So the only thing we can guarantee that a recepient will *see*
is what is in the first bytes with less reliability further out.
This places a priority on the left-justification of priority
data in all position and object comment fields.

Only the sender knows on any day, what parameters he wants
included, and which of those parameters are more important than
others.

So the USER should have the option to decide what info is the
-most- important and he should put that first.  Because only the
-first- part of a packet is guaranteed to be seen by all
applications.  The longer the comment text, the less likely that
all receive systems will display it.

So some people, /A=xxxxx altitude is very important to them, and
it trumps all else.  But for others, their FFF.FFFMHz frequency
may be more important, and their Tnnn tone, for others, their
Battery voltage may be more important, for others, their PHG
data.

When we added the /A=xxxxx to the spec in about 1995, we wanted
the user to have the option of placing this anywhere in the
comment string so that the user could still have more important
information first, but the altitude could still be included and
parsed if desired.

If an application or any tracker software wants to maintain the
flexibilty designed into the spec to allow the user to choose
the importance (display priority) of his data elemets, it should
give the user the option of where to put that data and not
arbitrarily force the user into only one location and hence
violate the intentions of the spec.

I hope that helps.

Bob, WB4APR





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