[aprssig] difference between Objects and Items?

Robert Bruninga bruninga at usna.edu
Wed Dec 10 18:16:01 EST 2014

ITEMS are shorter.  An brevity in APRS is always desired.

But there is a bug in tens of thousands of D700 radios that has a problem
with ITEMS.

I cannot remember for sure. (don’t have time to research it right now)…
But the bug MAY only be a problem if the ITEM uses compressed format.

So on sending, use an ITEM unless:

1)       the sender wants to time-stamp the object (always a good idea for
things that are not permanent and will eventually be of no value)

2)      The sender wants permanence 111111z

3)      The sender wants compressed.

I think I got that right?


*From:* aprssig-bounces at tapr.org [mailto:aprssig-bounces at tapr.org] *On
Behalf Of *Andrew P.
*Sent:* Wednesday, December 10, 2014 5:59 PM
*To:* aprssig at tapr.org
*Subject:* [aprssig] difference between Objects and Items?

Greetings, all.

I have a question for the long-time APRS wizards out there. What is the
difference between an Object and an Item (other than the message format
differences documented in the APRS Protocol Specification), and why would
you choose one message format over the other to report a non-station
entity? There doesn't seem to be much difference, conceptually speaking,
between an Object with a timestamp set to the originating station's
transmission time and an Item. Obviously, only Objects can be permanent,
since only they can have timestamps set to the reserved code for permanence

Due to this ambiguity, I may have an error in my APRS client program, and I
would like to correct this. Should the program infer use of Object format
versus Item format for locally-originated entities from the permanence of
the entity (or from other attributes), or explicitly require the user to
specify which format to use? On a "take-over" of another station's Object
or Item, should the Object versus Item characteristic be preserved in the
take-over? Are Objects and Items in different namespaces (i.e., can you
have an Object and an Item with the same name string and have them refer to
distinct entities)?

Thanks in advance.

Andrew Pavlin, KA2DDO
author of YAAC ("Yet Another APRS Client")
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