An OverView of Setting Up DosAPRS:

The Automatic Position Reporting System An Overview and Introduction                                   by Arte Booten N2ZRC (packet: N2ZRC@KB2VLX.#BRONX.NY.USA.NA)                 (E-mail: [email protected])

Many of you have heard discussions about a packet radio program called The Automatic Position Reporting System, (also called APRS.) It's a system which, unlike PBBS's, nodes and DX clusters, uses an UNCONNECTED protocol to transmit your exact position, a symbol denoting the type of station you're running and a Brief comment about it. It also uses direct keyboard-to-keyboard "chatting," has direction-finding capabilities and much more. How does it work? In its most simplistic form you transmit a packet which contains your callsign, exact latitude and longitude, information about your station's power, antenna's height, gain and pattern as well as a brief comment of your choosing along with some symbols necessary to make the system work. With this information your station appears graphically on a map (actually, one in a series of many maps) on the monitor as would other stations that are on frequency. Since this is an UNCONNECTED protocol, on-air packets can be kept to a minimum.

Consider this: When you connect to a local station using standard AX.25 you send a connect request to that station, they acknowledge that packet, send you a connected packet which you must then acknowledge. The same thing happens to EVERY packet you, or the other station, sends. With APRS you only send ONE packet to convey your information. If it's not received on the first transmission, APRS retransmits this information using a decaying time delay (that is, the second packet is sent eight seconds after the first, the third fifteen seconds later, the fourth thirty seconds later,, the fifth a minute later etc. until, after an hour, you're only sending six packets an hour!) This makes more efficient use of the frequency.

APRS uses different kinds of digipeaters, which use generic callsigns of RELAY, WIDE, TRACE, GATE and ECHO. RELAY stations (the default setting) are base stations used to digipeat low-power portable and mobile stations. WIDE stations will digipeat packets addressed either to their specific callsign or the generic WIDE to other VHF stations and WIDEs. A packet addressed to TRACE will, with a TNC with appropriate firmware, be digipeated, and the generic callsign will be substituted with the TNC's own callsign. An ECHO performs a function similar to that of a WIDE on HF. A GATE will digipeat from VHF to HF. When setting up APRS for your location you'll set your digipeater path based on the situation at that QTH and where you want your information to go. For keyboard-to-keyboard chats (which are the only comms in which "ACK's" are used) you can also set alternate digipeater paths. Not only does this direct your message via the shortest possible route, but it also reduces QRM.

The program also interfaces with popular weather stations such as those made by Davis and Peet Brothers, thus allowing for real-time weather data which is available at the touch of a key. The potential for this during a SKYWARN situation is obvious. You'll get wind speed and direction, temperature, rainfall amounts by the hour and 24-hour period and, in some cases, barometric readings. Such weather data can also be entered manually if a station has the information but not the hardware.

There is also a Direction-Finding mode which can be used by stations with either a beam or omni antenna! When the "fox" transmits, stations can call, by voice (on another frequency!) or keyboard their beam headings and/or signal strength. Using the antenna gain figures for these stations, circles are drawn on the map. The "fox" will usually be located where these circles converge. If you have one of the many "doppler" antenna systems they can also be used. If DX-ing is your thing, there's also a "DX-mode" which also uses the UI protocol by simply monitoring the DX cluster frequency. As new spots are posted, they appear on the map with their callsign. Their location is based on the callsign prefix of the spot. Obviously, since you're not connected to the cluster, this isn't meant as a replacement to your normal AX.25 program, and you can't SEND messages, you can receive them (the program will flag yours and display them when asked.) It's just another tool for your county- or country-hunting efforts. This feature is only available in APRS versions 7.96 or earlier.

If, like me, you have a Global Positioning System (GPS) receiver with NMEA-0183 output this, too, can be utilized with amazing results! Your mobile or portable position can be regularly updated. Using such a "stand-alone tracker" you don't even need a computer. All you'd need is an H-T, TNC and GPS! Think about the possibilities for such a setup in something like a marathon, walka-thon or even for someone shadowing an important official.

APRS was written to be able to run on just about any PC compatible computer from the latest Pentium Pro down to a lowly 8086. Heck, I know several people that use it with a Hewlett-Packard HP-200 palmtop! Maps are available from a large-scale map of the whole world to extremely detailed street-level maps. There's even a mail-reflector about it to which you can subscribe. Send a message to [email protected], with a body that reads "subscribe aprssig your_name" without the quotes and substituting your name for "your_name".

APRS is lots of fun, has many potential ARES/RACES/SKYWARN uses. I'm sure you'll enjoy playing with it!

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SOME REALLY SIMPLE BASIC INSTRUCTIONS ON GETTING APRS ON THE AIR

by Arte Booten N2ZRC (packet: N2ZRC@KB2VLX.#BRONX.NY.USA.NA) (E-mail: [email protected])

First things first. In order to run APRS, you first have to get it. If you have access to anonymous FTP simply navigate to the following URL: ftp://ftp.tapr.org/tapr/SIG/files/dosstuff/APRSDos and look for the latest version. In this example I'll use the nonexistent APRS version 9.99, which would be called "APRS999.zip." Substitute the appropriate file name for this.

If you're using PkZip204g, put your APRS disk into the floppy drive of your choice (I'll call it drive A) then expand the APRS files by using the following commands on the hard drive of choice:

Make an appropriate directory MD APRS

Change to this directory CD \APRS

Switch to the A drive A:

Run PKUNZIP with directories PKUNZIP -d APRS999.zip C:

Don't forget to use that "-d" switch, which lets it create the necessary subdirectories.

If you use WinZip, PkZip250 (or some other Windows-based zip utility, change to drive A and double-click on APRS999.zip, click expand button, tell it where you want it and follow onscreen directions.

Make sure your TNC is in Terminal or Command mode (whatever it's called by the manufacturer) and that parity is set to 8-N-0. At the C:\> prompt, go to your chosen APRS folder and invoke "APRS99.exe". If you're using Windows, simply double-click on that folder. This brings you to the LOGO screen. Enter your callsign and ssid, if any. Tell it what kind of TNC you're using. Answer the other various questions. When you're done, the main map screen will appear.

Now press M(aplist) then C(onfigure) and C(hange maplist), tell it you want to use the appropriate maplist for your area, either EAS(t), CEN(tral), WES(t), NE(ast), SE(ast), etc. Use the arrows or mouse to bring the cursor to your approximate location (keep your eye on the upper left part of the screen which shows the latitude/longitude of the cursor.) Then press HOME to center your screen on it. Use the PgDN key to zoom in a few screens and tweak the cursor to your EXACT QTH. You may have to zoom in to a very small scale to get the necessary resolution. Once the cursor is at the right spot hit the HOME key again.

Press I(nput) M(y) P(osition) and confirm your lat/long, choose a symbol for yourself, type in a brief comment, and verify it. Once you've pressed that "Y" you're essentially ready to go on the air. In it's most basic form, you'reconfigured! Tune the radio to 144.39 (in most parts of the country), hook it up and see what you can see. It might take a few minutes for other stations to appear (assuming there are some) but if you get a little impatient, try pressing O(perations) Q(uery) and give it a radius such as 64 to force position reports from others.

Look for stations whose symbol is a green star. THESE ARE THE WIDE DIGIPEATERS! Is there one fairly close to you? If there is, press the "D" key. If an asterisk (*) appears next to a callsign (hopefully that nearby WIDE) then you're hearing it directly. Make a note of that nearby WIDE station's digipeater path.

Now you're going to set YOUR digipeater path. Press O(perations) D(igipeaters). If you heard that WIDE station directly, enter it's callsign and ssid, if any. Follow this with a comma then type in "WIDE". For example: KF4INN-10,WIDE would be how I'd enter it here in The Lex Area, but the nearest WIDE to YOUR QTH is what YOU'RE looking for.

Next you want to set your Power-Height-Gain figures. Press I(nput) P(ower) and tell it how many watts you're using, your antenna's height above AVERAGE terrain (look at a topographical map of your area,) the gain in dBd and the antenna's directional pattern in degrees or 0 (zero)for an omnidirectional antenna.

Finally, set your Beacon Text by pressing I(nput) M(y) S(tatus) and typing in a short comment, different than the text you used for your Position Text earlier. At this point, you're about as far as you need to go for now.

I hope to see you all on my screen in the VERY near future. Look for me at cruise missile coordinates 3802.38N/08442.55W 73s ============================================================================= APRS: Using It (or: Now that I've got it set up, how do I make it work for me?) by Arte Booten N2ZRC (packet: N2ZRC@KB2VLX.#BRONX.NY.USA.NA) (E-mail: [email protected])

In other articles I've described what The Automatic Position Reporting System is and how to get it set up on your computer and radio. So you're now probably telling yourself "OK, great. I've got these stations appearing on my screen. Now what do I do?"

One of the features in APRS is the ability to send what we call oneliners; that is, one-line messages from station to station either direct or by using digipeaters. From the main APRS screen press S(end), type the station's call and <cr>. Then type your message and another <cr>. You'll know when they got it when you receive an *ACK* which replaces the first five characters of your message. These one-liners are the only situation when APRS uses anything other than UI packets.

When you send a message in this manner it will be sent via the same digipeater path as your position and ID packets. If your intended recipient is someplace else you can STILL send it there by specifying an alternate digi peater path, which the program can store for you. If you press O(perations) D(igipath) S(ave), you'll be prompted to enter a two-letter code for that path via whatever path you choose, such as: NJ VIA KC2CWT-15,N2MH-15,KB2EAR-1,W2HOB-15 to get to Southern New Jersey from Northern Westchester. To see which paths you've stored, press O(perations) D(igipath) L(ist). The main purpose of these alternate paths is to keep the QRM to a minimum and to use the most direct and, sometimes, the only feasible path.

The weather systems feature of APRS allows you to see various weather information in real-time which is transmitted by stations with a Peet Bros. or Davis Weather Station. Depending on which version of APRS you're using (as of now, July 1998, it's 8.17) and the options the weather station has, you can get different kinds of information including temperature, rainfall amounts (to the 1/100th inch) in the past hour and 24 hour periods, wind speed, direction and gusts and barometric pressure. By pressing W(eather) I(cons), or W(eather) D(isplay), you'll see a list of options to choose from. These have changed for the better) in the last few versions, so I can't be specific.

If at any time you wish to cease transmitting without actually shutting down the program, simply touch C(ommands) X(mit). This will disable the timer within APRS. When you want to send a specific packet (most often your position), you can do so by pressing X(mit) P(osition) [or S(tatus), M(essage), O(bject) or A(ll), as the case may be.]

In order to find a station on the screen, you can always use the O(perations) F(ind) (what else!) command. If you want to see something really neat, try O(perations) R(eplay), and type in the callsign of a mobile station. What you'll see the station's track being replayed. To access your TNC you'd use O(perations) C(omms) T(NC) which leads you to a very basic terminal screen. To get stations to appear on your screen faster (within two or three minutes) use O(perations) Q(uery), followed by a radius in miles from you.

Now that you've been on the air with APRS for a few hours, you don't necessarily want to wait for all those stations to reappear if, for some reason, you have to exit the program. No problem. When you shut down APRS by pressing Q(uit) Q(uit) <cr>, it asks you if you want a backup of this information, which it does by default. Next time you fire it up, you press F(iles) L(oad) B(ackup). Every time you shut APRS down it'll save this file, replacing the previous copy. Be aware, though, that all of those packets are time-stamped, and any station's data in this backup that was heard more than two hours ago will "gray-out" (APRS considers them to be inactive and makes room for more stations that way.)

One thing to remember when playing with APRS is that the best way to learn, as with anything else, is by doing. You can play with the commands as much as you want. You're not going to BREAK anything! About the worst thing that can happen is a lockup, and this is a rare thing. Usually the three-fingered-salute (Ctrl-Alt-Del) will get you out of it and you'll have to start over. So play with the thing. I mean, how do you think I learned all this about APRS stuff, by reading about it?

Speaking of reading about it, yes I did. It's all right there in the APRS distribution zip file. You can always read those files by pressing F1 F(iles) and typing in the name of the file you want to see. One suggestion: if you're a slow reader, press the down-arrow button once in a while as APRS seems to get impatient with you when it just sits there while you re-read that paragraph for the umpty-umph time and shoves you back into the program.

There are dozens of these readme files in the "README" folder. You can also see them (at your leisure and there for the printing) by using any old text editor. Many of the answers to your questions can be found there, sometimes buried deep and not quite as visible as you'd like.

You can also purchase "Getting On Track with APRS", which was written by none other than Stan Horzepa (WA1LOU). It's available at many ham radio shops as well as your local hamfest. Or you can order it directly from the ARRL. Stan's book will walk you through much of what you'd like to know, in somewhat more detail than I can here. Mr. Horzepa is the author of "Digital Dimensions" in QST magazine, and also runs the WA1LOU-15 digipeater in Wolcott, CT.

I hope you enjoyed this series on APRS and hope to see you on the map in the near future. Whenever I see a new station on the screen I try to send them a one-liner welcoming them to APRS and offering live assistance and advice. Feel free to take advantage of this, or ask questions of any station on the air at that time. We're all very excited about this program and think that "the more, the merrier" is the way to go. We've gotten a lot of "converts" in the last few years and this situation can only improve, so come and join us on 144.390! 73s

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