[aprssig] PIC processor for APRS info for D-STAR mobiles?

Pete Loveall AE5PL Lists hamlists at ametx.com
Sat Jul 5 06:52:54 EDT 2008

So the group understands, the D-STAR protocol is not made available to radio users.  A TNC makes the AX.25 protocol fully available to a user so things like APRS can be implemented.  The reason is AX.25 is a -data- protocol and the TNC is simply a modem with some extra logic to simplify access to the AX.25 protocol.

A D-STAR DV (digital voice) radio uses the D-STAR protocol to provide reliable -voice- communications between radios.  The protocol overhead such as the RF header is not made available to the user as it is integral to the proper operation of the radio.  Icom allows a user to preprogram a message into a radio that will display every time the user transmits.  This message is displayed on the remote radio's front panel IF the remote radio has this ability enabled (and IF it is capable).  What Bob refuses to accept is the fact that this information is not carried over the portion of digital voice stream the user has access to.  It is completely hidden.  The radios in GPS mode also expose this information (callsign and canned message) over the user accessible data portion of the digital voice stream, but the radios do not use this exposed information.  The radios continue to use the hidden transport mechanism for displaying callsign and this canned message.

This significant difference in the protocols and how they are exposed is why trying to use the radio's display for 2-way communications is not only futile, it is misguided and exhibits is a strong lack of understanding of how the D-STAR protocol is designed and how Icom implemented their -complimentary- data capabilities.  Bob approached me on this subject over a week ago and I provided this same information.  Unfortunately, he refuses to understand the fundamental differences in the protocols and the radios as demonstrated by his post to this group.  I am sorry that someone who this group highly respects would push logic and understanding aside to pursue something that has already been explained to him why it does not work that way.


Pete Loveall AE5PL
pete at ae5pl dot net

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