It is important on APRS to use a unique -SSID for each "station" that you operate. If you don't, consider the effect when one station moves and the other station remains behind. The station appears to ping-pong between two coordinates with each position update sent.

This is especially true if you are running both APRSISCE on Windows Mobile and APRSIS32 on Win32. Obviously the former station is mobile and the latter station is most likely fixed. Whenever you leave the house, if both clients are running, you will appear to be on a rubber band between your actual position and the fixed station.

This is also true if you have APRSISCE/32 connected to a device that generates its own APRS packets (like a Tracker2 or TT4 or Kenwood). However, if your running APRSISCE/32 as an Internet-ONLY connected station, you are not bound to the -0 through -15 numeric limit. You can use ANY -SSID, including alpha (I personally run -AL, -AP, and others). Anecdotal evidence suggests that some mobile (Yaesu's FTM-350r for instance) cannot send a message to a non-AX-25-compatible SSID even though the destination of the message is sent outside the AX.25 header.

You MUST use a NUMERIC -SSID in the range of -0 (same as no -SSID) through -15 if you have any RF interfaces configured for transmit. This is (currently) KISS, TEXT, or AGW interfaces and may expand to others (BPQ for instance) in the future.

The following list was copied from APRS SSIDs:
(it was last edited on, 6 February 2012 when I copied this info)

It is very convenient to other mobile operators or others looking at callsigns flashing by, to be able to recognize some common applications at a glance. Here are the recommendations for the 16 possible SSID's (the limit of 16 comes from the 4 bits available in the AX.25 protocol. Note, The SSID of zero is dropped by most display applications. So a callsign with no SSID has an SSID of 0.

SSID Description
-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
  • One-way trackers should best use the -12 one-way SSID indicator because the -9's usually mean a ham in full APRS communication both message and voice. The -9's can be contacted by APRS message or by Voice on his frequency included in his beacon, or on Voice Alert if he is in simplex range. The -12's are just moving Icons on the map and since they have no 2 way communication for ham radio they are not generally of routine interest to other operators.

OBJECTS or INTERNET: In addition, Objects or internet generated stations can have any SSID, not just the original 16, since Objects are not constrained by the AX.25 header and can have a 9 byte name. Here are some common OBJECT/Internet SSID's:

SSID Description
-63 PSK63 HF stations
-tt APRS TouchTone users (DTMF)
-A-Z Dstar
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