[aprssig] APRS Message Callsign SPEC- Ambiguity

Pete Loveall AE5PL Lists hamlists at ametx.com
Tue Apr 26 19:29:56 EDT 2016

#4 is incorrect.  The transmitting callsign-SSID (your term "his TNC call") MUST be AX.25 compliant on RF and MUST match the APRS message addressee callsign-SSID that is being acked (see below).  In other words, the following will work:

AE5PL-15>APRS::WB4APR-5  :test message{01

Because the ack will be:

WB4APRS-5>APRS::AE5PL-15   :ack01

But the following will NOT work:

AE5PL-15>APRS::QIKCOMsay:test message{01

Because there is no way to transmit on AX.25:

QIKCOMsay>APRS::AE5PL-15   :ack01

Note that message numbers are not only tied to the message but also to the addressee so WB4APRS-5>APRS::AE5PL-15   :ack01 would be meaningless to AE5PL-15.  I know you believe that all message numbers are unique but they can't be for a service because of the number of messages that station might generate every day causing rollovers, etc.  Also, radios like the early Kenwoods and many software packages won't recognize a message with a duplicate message number as being new even if it has new content.  Because of these constraints, most software won't consider an ack as valid for a message sent to an addressee when that ack is from a station different from the original message addressee.

Like it or not, that is the way it works with most radios and software.


Pete Loveall AE5PL
pete at ae5pl dot net

> -----Original Message-----
> From: Robert Bruninga
> Sent: Tuesday, April 26, 2016 4:47 PM
> Subject: Re: [aprssig] APRS Message Callsign SPEC- Ambiguity
> Summary of APRS Messaging Constraints on the 9 byte To-ADDEE Field:
> APRS Message SENT to a mixed case or non SSID 9 byte TO-ADDEE field:
> 4) RF ACKs from the 9 character ADDEE will work because the ACK is sent from
> his TNC call to the sender's TNC call

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