Since there are 20,000 APRS users on the air, the APRS maps and data can get very cluttered. Also, most operators have multiple stations on the air, such as their HOME, CAR, BOAT, and HT. It is very convenient to be able to recognize these typical applications at a glance. See also the Symbols and SSID page on the info.aprs.net Wiki.

Here are those common defaults:

SSID Application
-0 Your primary station usually fixed and message capable
-1 generic additional station, digi, mobile, wx, etc
-2 generic additional station, digi, mobile, wx, etc
-3 generic additional station, digi, mobile, wx, etc
-4 generic additional station, digi, mobile, wx, etc
-5 Other networks (Dstar, Iphones, Androids, Blackberry's etc)
-6 Special activity, Satellite ops, camping or 6 meters, etc
-7 walkie talkies, HT's or other human portable
-8 boats, sailboats, RV's or second main mobile
-9 Primary Mobile (usually message capable)
-10 internet, Igates, echolink, winlink, AVRS, APRN, etc
-11 balloons, aircraft, spacecraft, etc
-12 APRStt, DTMF, RFID, devices, one-way trackers*, etc
-13 Weather stations
-14 Truckers or generally full time drivers
-15 generic additional station, digi, mobile, wx, etc

Originally, in 1992, the first APRS GPS mobiles just transmitted raw NMEA-0183 GPS stings and so there was no way to insert a SYMBOL byte in the pre-formatted NMEA 183 packet. Hence we defined 14 common SYMBOLs as defaults to the 14 available SSID's that a mobile could use. These included BIKES, HELICOPTERS, AIRCRAFT, VANS and many others in addition to the ones above. This is now OBSOLETE.

In the late 1990's we came up with a better solution and defined the AX.25 TOCALL of GPSxyz for such use. In this case, the "XYZ" characters can be used to define any of the hundreds of APRS symbols including Overlays. Just look up the XYZ in the SYMBOLS.TXT file included in all copies of APRSdos (or these days, on the WEB).

Since this GPSxyz concept was so powerful, it completely replaced the original SSID assignments and so those original NMEA defaults have been removed from the Documentation.

However the convention for the 6 most useful ones remains and should be used in the absesnce of any other overriding conditions. Except for the TH-D7 and Truckers, the other SSID conventions mark APRS "TYPES" of users that are independent of the many SYMBOLS they can use. Thus it is nice to know HOW someone is getting into the system, whether via satellite, HF, the Internet, or touchtone. For example, using the -6 only for Space applications is so that the global APRS WEB data bases will keep statistics and data for when you are operating through the satellites separate from when you are working normally.

So stick to the standards above for the obvious applications… Of course these are not rigid. If you have more than 4 digipeaters, use any SSID you want. These are only guidelines…

de WB4APR, Bob

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