As my friend Cory Sickles WA3UVV eluded to in his article in the June issue of Crosstalk (the newsletter of the Gloucester County Amateur Radio Club), APRS did indeed contribute to the demise of traditional packet radio (along with the advent of ubiquitous Internet e-mail). Like traditional packet radio, APRS is an underutilized yet very valuable ham radio tool that still has much useful life left in it.
While traditional packet radio and APRS are both built on the same underlying technology, they way they both operate and their use cases are very different. Traditional packet radio is connection based, to communicate with another station you must issue a connect command like [C]onnect WA3UVV. This establishes a virtual circuit between my station and Cory's, when my station sends a packet his station will [ACK]nowledge it. This back and forth continues while data is flowing between the two stations. When the session is complete I [D]isconnect from WA3UVV and both stations are available for use. This same paradigm works whether it's two user stations connecting or a user connecting to a digipeater or BBS. Unless specifically configured, the TNC will only support 1 connection or virtual circuit at a time. While in a connected state, the TNC will not show me any other traffic going on the frequency, unless I specifically send a command to enable that functionality.
Conversely, APRS is a connectionless (or broadcast) system. There are no ACK messages passing between two stations, all packets are a special type called UI (Unacknowledged Information) and simply launched into the ether. Since there are no virtual circuits or connections, all the information that needs to be sent must fit into one packet, making brevity the watchword for operation in APRS. Since there are no connections in the APRS flavor of packet radio, you see all the traffic going on around you, and that is by design. Bob Bruninga WB4APR, the creator of APRS, had the concept of a real time information exchange system; the free exchange of data throughout the system is the value proposition of this mode. Connected mode packet radio excels for message transmission, especially when the person you want to communicate with is not on the air (just leave the message on a BBS or personal mailbox). The meat and potatoes of APRS are things happening and people participating in realtime. Fortunately for anyone interested in either mode, you don't have to make a choice, the equipment for both is the same, just use different (free) software.
Cheap GPS receivers are the single greatest cause of the boredom of APRS. Bob Bruninga has ranted (for years) that APRS stands for Automatic PACKET Reporting System, not Automatic POSITION Reporting System. Users can participate fully in the system without a GPS, the introduction of cheap GPS receivers got everyone distracted with vehicle tracking and losing sight of all the other rich features available. Bob's design intent was for a system that hams could use to find out about whatever interesting things are going on in their area. Broadcasting about nets, meetings, text messages, weather and road traffic information, local voice repeater information, and points of interest locations are all examples of valuable ham radio situational awareness items. Are several hams at a diner for lunch and want to let other hams know to come on down? Put it on APRS! Having a tech session at the club house? Put it on APRS! Rag chew net coming up? Put it on APRS! Want to show people where the hamfest is? Put it on APRS! If you use Twitter, anything (ham radio related) that you might tweet about would work great on APRS. I could go on but I think you get the idea.
Here are some examples of behaviors I have seen, using APRS, that contribute to increasing the boredom factor:
Broadcast the position of your car, 24x7, especially if you are not in it. Really, I couldn't care less where your car is if you aren't in it.
Broadcast the position of your house, 24x7, especially if you're not home. Again, if you're not available to communicate what's the point? Though if your house starts to move you probably have larger issues to be concerned about.
Broadcast a message that says "station unattended". Stating the obvious is not a real effective way to win friends or influence people.
I don't mean to sound like the grumpy old man here, or the arbiter of all things APRS, but my simple rule is "if I'm available to communicate, the APRS is on, if I'm not, it's off".
APRS can be an exiting adjunct to other ham radio activities by letting other hams know you're doing something interesting, fun, or of service to the community. You can advertise what repeater you are listening to, have a text message chat with a friend, or let people know of a traffic jam on a busy road. The possibilities are limited only by your imagination. If you'd like to know more, e-mail email@example.com or send an APRS message to K2ZA-1.