The Automatic Position Reporting System (APRS)

by Tom Weeden, WJ9H

#2 - Getting Started


Last month we talked about the APRS concept and how it is revitalizing VHF packet radio. This month we'll get the DOS version of APRS up and running. If you have a DOS machine, 8088 or better, plus a CGA or better monitor, already running your favorite terminal program for packet, you're all set. As of this writing, the current version of APRS is 8.32. You can download it from the TAPR site by going to:

ftp://ftp.tapr.org/aprssig/dosstuff/APRSdos
and downloading: APRS832.ZIP [Note: as of June 2000, the current version is APRS846.zip]

While you're at the TAPR site, also go to the following directory:

ftp://ftp.tapr.org/aprssig/maps/PCMaps and download the map file: WIMAPS03.ZIP

Now, create a new directory called \APRS and put the two zip files into it. UnZIP the files with the PKUNZIP utility:

PKUNZIP -D APRS832.ZIP
PKUNZIP -D WIMAPS03.ZIP

Make sure you use the "-D" switch which places all the files in their proper subdirectories. (If you don't have PKUNZIP.EXE to do the unzip, try the www.pkware.com web site and download PKZIP 2.04g for DOS.)

Are you ready to start? Set up your radio to 144.390 MHz, turn on your TNC and make sure it's connected to your computer. From the \APRS directory, type APRS830 and the program will start. You'll be prompted for several pieces of information. First is your call. Next, which COM port is your TNC on? What is its baud rate? (Enter the baud rate your computer uses to talk to the TNC.) Will you be on HF or VHF? Answer VHF for now unless there is no activity in your area. Then answer HF only if you have HF packet capability. What type of TNC are you running? Pick the closest from the list by typing the first letter of its name. Is your PC clock on local time or UTC? Then your UTC offset: if you're in Wisconsin, it's -6 unless we're on Daylight Savings Time, then enter -5. Will your other COM port be used? Right now, answer None.

Now you should have a simple map of the USA with a cursor in the middle. Let's go over some of the display screens before we zoom into your location.

* P shows the POSITION screen. This is a list of all stations' position packets.
* L shows the LIST of status, log, DX, or telemetry packets which are non-position packets.
* D shows the DIGIPEATER list, the paths of all stations heard.
* B shows any current BULLETINS that stations may have sent.
* H shows the HEARD page, a list of hourly statistics from each station.
* A shows the list of ALL packets.
* F1 gives HELP! Press F1 then H for a quick summary of one-letter commands. F1 then F gives a list of README-type files that you can read for more detail.
* Pressing the SPACE bar will redraw the current map.
* Pressing the HOME key will redraw the current map centered on the cursor location.
* Pressing the PAGE UP key will zoom out by a factor of 2 centered on the cursor location; PAGE DOWN will zoom in by a factor of 2.
* Q is for QUIT.

Let's see if we can find your location. Press SPACE to get back to the map page (if you left it). Now press M (MAPS), C (CONFIG), C (CHANGE MAPLIST), then enter WI for the WISCONSIN list of maps. Using the arrow keys, position the cursor over Wisconsin and press PAGE DOWN. As you zoom into your location, more detailed maps may open up if they are available for your area. Keep refining your position and pressing PAGE DOWN until you are satisfied that you have found your location.

Now press I (INPUT), M (MYDATA), P (POSITion). You will see a latitude value which you can accept by pressing ENTER, or you may enter your own latitude value. The same will happen with the longitude. Next you'll be prompted for a symbol letter. Press Q for QTH and then pick the number corresponding to your antenna type. Now, what's your course and speed? Your house is stationary, so press ENTER for the values of 000 and 000. Next, you can enter some brief text such as "Tom in Madison" or similar. And finally, you'll be asked for a date/time stamp; press ENTER for NOW. Now press Y if all your data is correct or N to start over. Pressing Y formats the position packet and tells the TNC to send it. Congratulations! You're on APRS!

There is more you can add to your position and status packets. First is Power-Height-Gain. Press I (INPUT), P (PWR-HGT-GAIN) and follow the prompts. You can also enter a status packet by pressing I (INPUT), M (MYDATA), S (STATUS). If you don't enter a status line, the L-list will show "NONE" for your status.

The timers in the upper right hand corner of your screen will tell you how long until the Position and Status packets will be sent again. Notice that if your information doesn't change, the interval between packets continues to increase so as to not "clog" the frequency.

As you see stations begin to plot on your map and add to your station lists, you'll see who is within range and who you could use as digipeaters to get out farther. APRS uses generic aliases of RELAY and WIDE. If you see a WIDE station within range, use the U (UNPROTO) command to specify a path. At first, try RELAY,WIDE or WIDE,WIDE to see which works best. Or specify the callsign of a nearby station and add WIDE (such as K9XYZ,WIDE).

What if there are no VHF stations within range on APRS? Try HF! The most popular HF frequency is 10.151 MHz. Wait a minute: that's out of band! Well, not quite. The dial frequency is 10.151, but the mode is lower sideband, putting the MARK tone at 10.1492 MHz, just inside the band! There are also some 40- and 20- meter frequencies to try. Use the F1-F command to read the HF.TXT file for more information.

In fact, feel free to use F1-F to peruse the various help files as you play with APRS.

Now, for you Windows and Mac users. There are versions for you to try. I won't be going into them in detail, but here are the sites to get the software.

WinAPRS

MacAPRS
 

Next month, we'll discuss in more detail APRS digipeater paths and how to send messages.

This page originally appeared in April 1999 Badger State Smoke Signals but was updated 2000 June 14.
Copyright 1999, 2000, Thomas C. Weeden, WJ9H