One of my favorite sections of Amateur Radio is APRS. The Automatic Packet Reporting System. The brainchild of Bob Bruninga. The very first version was written by Bob in QBASIC for the DOS platform (platform?). There are now exsisting versions of APRS for DOS, Windows, Macintosh, Linux, Palm OS and even Windows CE. Personally I use the DOS, Windows and Palm OS versions. I like the DOS versions the best. They are somewhat primative compared to the Windows and Mac versions, but I learned with the DOS version and I guess old habits are hard to break :o) The Windows version is great for the laptop and works great when the TCP/IP link is enabled for watching APRServer activity. The TCP/IP function allows you to look at the APRS activity all over the world without have a TNC and radio connected. I use the Palm OS version for any portable operations. Take a look at my Portable Packet page for an explanation of how I use my palmtops for portable packet.
The KPC-3 is the easiest TNC to setup for any APRS operation, a Digi is easy takes almost no time. First, the best way to start is to do a HARD RESET to set the TNC back to factory parameters. Then connect the TNC to a computer with a terminal program such as HyperTerminal in Windows. I even use my palmtop to program my KPC-3 in the field if required. Set the INTERFACE to TERMINAL mode. The table below maps out the minimum simple parameters to set. For MYCALL you enter in the call of the digi along with an numeric identifier such as 5 or 10, if requiered. For an example, I have my digi set as KE4NYV-5. MYALIAS can also be used for an alternate alias such as NODE. Here in Virginia some digi's are now starting to use the alias VA so you can go anywhere in state and as long as you have VA in your PATH, you can get a digipeat. Beacon time sets the time between beacons. The number is in seconds, so 60 would allow for a beacon every minute. The UNPROTO is the digipath for the digipeater. This will determine how the digipeater's digipeats will travel through the APRS network. The PATH can be a gerneric path such as RELAY,WIDE,WIDE or can contain the calls of other digipeaters in the area. Such as in my area, I could use somthing like RELAY,N2EDE-3,WB4QOJ-2. You must pick a path that will allow for the best coverage.
|KPC-3 Digi Parameters|
|UNPROTO||APRS VIA PATH|
BEACONTEXT or BT is what contains the digi's posistion, icon identifier, antenna info and status or comments. This is the last parameter that needs to be set into the TNC. If this is not entered, the Digi will NOT show up on an APRS map. The "#" is the icon identifier, any indentifier can be used but the "#" pound symbol is the indentifier for a digipeater. It will place a green star icon on an APRS map.
|BT||!DDMM.mmN/DDDMM.mmW#PHG5555/comments or status|
This is a picture of my APRS setup, I don't always have this much going, but there is enough here to spark interest. From left to right: Compaq laptop running WinAPRS connected to the APRServer, Compaq 486 running PBurst to display the incomming packet data as well as any other activity in the local network, Kantronics Kam Plus multi-mode TNC, IBM Thinkpad 486 running DOSAPRS. I split the output of the Kam Plus to feed the laptops that the Kam Plus is between. If you look right to the right of the IBM machine, you can see an HTX-202 and my TinyTrak, it's hooked to a Garmin 12 which is sitting on the window cill, just out of the shot on the right.
APRS Touch Tone is a concept that was first introduced by Bob Bruninga WB4APR at the 2002 Dayton Hamfest. I was able to be there to see it first hand and demo'ed by Bob himself. The concept is that regular HT's and mobiles that are equipped with DTMF encoders can send DTMF strings to a server that will in turn send out an APRS formatted packet.
A Little more detail...
By use of DTMF strings a station can send it's call, position and even a message. This is spelled out very well in Bob's spec sheet that can be found here. The spec sheet also has several circuits that are needed to make APRStt work. The circuits include a 8880 based DTMF decoder, resistor ladder network or DAC IC for the "voice out" and 2 PTT circuits for keying the transmitter.
Below is a picture of a PCB that was drawn up by Wes Johnston KD4RDB. This the board that I built up. The PCB includes all four circuits that run off of the computer's parallel port. Instead of using the ladder network, Wes chose to use the Maxim MX-7524 DAC IC to convert the digital bits from the LPT1 port to audio.
Below is a parts list and placement diagram for the TT Interface board.