[aprssig] Icom D-STAR GPS Mode and APRS

AE5PL Lists HamLists at ametx.com
Sat May 28 08:24:32 EDT 2005

As some of you may know, the Icom 2m and 440 D-STAR compatible radios
support a mode they call GPS mode.  As some of you may also know, this
mode is not APRS compatible, either in the format of the data or the
data transport mechanism.  I was asked to investigate whether a gateway
could be created so those radios could be used as trackers to the APRS

I am pleased to announce that I am releasing today a new "TNC" interface
for javAPRSSrvr which supports converting the Icom position strings to
an APRS position packet and then passing only the posit to APRS-IS.
This turned out to be the most straight forward method of getting the
multi-line Icom data into APRS-IS.

As it turns out, the GPS data can share the same channel with real APRS
clients connected to the data port of the radios!  I have set the "Icom
interface" to pass all TNC2 formatted lines to APRS-IS in addition to
the converted Icom posits.  And, of course, all TNC2 format packets from
APRS-IS can be gated to the Icom radio just like a regular IGate.  What
does this do?  It allows people with APRS clients to connect to their
"low speed" Icom D-STAR radios and operate just like they were on an
APRS channel (without all of the clutter, of course, as there is NO
source routing).

The "Icom interface" can also be set to "echo" the APRS formatted posit
created from the Icom GPS data back to RF.  This allows those people
with APRS clients to see all of the local D-STAR "trackers" along with
all gated traffic.

Can this data be gated to 144.39 (or your common APRS frequency)?  Yes.
javAPRSSrvr supports gating to RF based on "IGate of origin".  This
would allow gating to the APRS frequency all RF originated packets
received from the local D-STAR channel.

This post is not intended to promote or disparage the Icom D-STAR
radios.  Instead, it is simply an announcement that we have been able to
implement an APRS/D-STAR GPS gateway which also will allow the D-STAR
radios to be seamlessly used with standard APRS clients.


Pete Loveall AE5PL
mailto:pete at ae5pl.net 

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