Subj : APRS Overview
To : All
From : Daryl Stout
Date : Wed Jul 22 2020 10:13 am
For those using APRS, I am located at:
Latitude : 34 degrees 70 minutes 09.53 seconds North
Longitude: -092 degrees 32 minutes 89.40 seconds West
***
The Automatic Position Reporting System
An Overview and Introduction
by Arte Booten, N2ZRC <n2zrc@arrl.net>
Many of you have heard about a packet radio program called The Au-
tomatic Position Reporting System, (also called APRS.) It's a system
which, unlike a BBS, node and DX cluster, 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 keyboard-to-
keyboard "chat", has direction-finding capabilities and much more.
How does it work? In its simplest form, you transmit a packet con-
taining your callsign, exact latitude and longitude, information on your
transmitter's power, antenna height, gain and pattern as well as a brief
comment of your choosing, along with some symbols which make the system
work. With this information your station appears graphically - on a map
(or one in a series of many maps) on your computer's monitor. It'd al-
so appear on the screens of other stations that are on frequency. Your
station would similarly appear on theirs. Since APRS uses an UNCONNECTED
protocol, on-air packets can be kept to a minimum.
Consider this: When you connect to your local node, using standard
AX.25, you send a connect request to it. It'll acknowledge that packet,
then send you a connected packet which you must then acknowledge. This
same thing happens with each and every packet you, or the other station,
send.
With APRS you need send only ONE packet to convey your information.
If it's not received on the first transmission, APRS retransmits it, us-
ing a decaying time delay (that is, the second packet is sent eight sec-
onds after the first, the third fifteen seconds later, the fourth half a
minute later, the fifth a minute later, the sixth two minutes later etc.
until, after two hours, you're only sending three packets an hour!) It
makes more efficient use of the frequency.
APRS uses several different kinds of digipeaters in order to propa-
gate beyond their immediate area. They use aliases such as RELAY, WIDE,
TRACE, ECHO and GATE. There are also variations of WIDE and TRACE known
as WIDEn-n and TRACEn-n. A RELAY station (the default setting) are us-
ually base stations, and are used to digipeat low-power portable and mo-
bile stations. They are an essential part of the APRS system as a whole
which is why most versions of APRS default to it.
WIDE digipeaters retransmit packets addressed either to their spe-
cific MYCall or the generic WIDE to other local VHF stations and WIDEs.
Some have the ability to change that generic WIDE to its own MYCall.
ECHO stations performs a similar function on HF. GATEs retransmit
signals from HF to VHF. However, they should NEVER be used to retrans-
mit from VHF to HF. This is because VHF APRS uses 1200-baud signals on
144.39 MHz in most parts of North America. HF APRS uses 10.151 MHz LSB,
just inside the upper edge of the 30-meter band, which is limited to us-
ing a maximum of 300-baud.
When setting up APRS for your location, you'd set your digipath based on
the situation at that QTH and where you want your packets to go. In us-
ing keyboard-to-keyboard communication (the only comms that use "ACK's")
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, showing real-time weather data at
the touch of a key. The potential for this during SKYWARN situations is
obvious. You'll get wind speed and direction, temperature, rainfall am-
ounts by the hour and 24-hour period and, in some cases, barometric rea-
dings. Such weather data can also be entered manually if a station has
the information but not the hardware.
There's 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 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 at the
converge of these circles. If you have one of the many "doppler" anten-
na systems, they can also be used.
If DX-ing is your thing, there's a "DX-mode" which also uses the UI
protocol by simply monitoring the DX cluster frequency. As a new spot is
posted, they appear on the map with their callsign, based on their pre-
prefix. Obviously, since you're not connected to the cluster, it's not
meant as a replacement to your normal AX.25 program, and you can't SEND
messages, but you can receive them (the program will flag yours and dis-
play them when asked.) It's just another tool for your county- or coun-
try-hunting efforts.
If you have a Global Positioning System (GPS) receiver with NMEA-
0183 output this, too, can be utilized with amazing results! Your mob-
ile or portable position can be regularly updated. Using a stand-alone
tracker (including radios such as Kenwood's TH-D7a HT and TM-D700 mobile
rig) you don't even need a computer. All you need is an H-T, TNC and a
GPS! Think about the possibilities for such a setup in something like a
marathon, walkathon or even for someone shadowing an important official.
The DOS version of APRS was written to be able to run on just about any
PC clone from the latest Pentium IV 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 extreme-
ly detailed street-level maps. It's lots of fun, has many ARES/RACES/
SKYWARN uses and I'm sure you'll enjoy playing with it!
SOME REALLY SIMPLE BASIC INSTRUCTIONS ON GETTING APRS ON THE AIR NOW
by Arte Booten, N2ZRC <n2zrc@arrl.net>
In order to start using APRS, you'll need the following equipment,
much of which you may already own:
I. A two-meter transceiver. Neither CTCSS nor frequency agility
is necessary. Lots of older rigs, particularly HT's, can be had for al-
most nothing at hamfests.
II. A TAPR-2 compatible Terminal Node Controller (TNC). This cov-
ers practically every TNC built for the past fifteen or so years. Kan-
tronics, PacComm and AEA are popular brands to choose from. Older ones
can also often be found on tables at a 'fest.
III. A computer. There are versions of APRS written for Macintosh,
Windows, Linux, WindowsCE and the Palm OS. The DOS version, however, is
able to run on practically *any* PC-compatible computer ... even ancient
8086's! These articles focus on APRSDos (which runs just fine under Win
3.x, 9.x, NT and 2k and Linux (using dosemu), and the following descrip-
tions are for installing it and getting it running on a PC.
IV. Assorted cabling, power supply, antenna, etc.
V. The program. Simply point your browser at the archives of The
Tucson Amateur Packet Radio organization (or use FTP), by going to:
ftp://ftp.tapr.org/aprssig/dosstuff/APRSdos/
and look for the latest version. It ought to be just large enough to be
able to fit onto one floppy disk. While there, go up a few levels, then
burrow down into the Maps/PCmaps area. You'll find a file there called
"nynyc01.zip", which contains street-level maps of most of New York City
made by the author of this article.
At this typing, the current APRS for DOS version is 8.48...called
"APRS848.zip." It can be downloaded from the Main Menu prompt.
If you use PkZip204G or PkZIP 250, put the APRS disk into your
floppy drive of choice (I'll call it drive A) then expand the APRS files,
using the following commands on the hard drive of choice (C in this
example):
Change to the root directory C:\>CD\
Make an appropriate directory C:\>MD APRS
Change to this directory C:\>CD \APRS
Switch to the A drive C:\>A:
Run PKUNZIP with directories A:\>PKUNZIP -d APRS848.zip C:\APRS
Don't forget to use that "-d" switch. This lets it create the nec-
cessary subdirectories.
If using WINZIP, change to drive A and double-click on APRS848.zip,
click the expand button, tell it where you want APRS to live and follow
onscreen directions.
Make sure your TNC is in Terminal or Command mode (whatever it's
called by the manufacturer.) At the C:\> prompt, go to your chosen APRS
folder and invoke "APRS848.exe". If you're using Windows, just double-
click on that file. This brings us to the LOGO screen. Enter your call
and SSID, if any. Tell it which TNC you're using. Answer the other
various questions. When you're done, the main map screen will appear.
Now press the arrow keys (or use your mouse) to bring the cursor to
your approximate location (keep your eye on the upper left corner of the
screen which shows latitude/longitude of the cursor.) Then press HOME
to center the screen on it. Use the PgDN key to zoom in a few screens
and tweak the cursor to your EXACT QTH. 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. Then pick
a symbol for yourself, type in a brief comment, and verify it. Once you
press that "Y" you're essentially ready to go on the air. In it's most
basic form, you're configured! Tune the radio to 144.39, 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 X(mit) Q(uery) and give it a radius such as 64 to force posi-
tion reports from others.
Look for stations whose symbol is a green star. THESE ARE THE WIDE
DIGIPEATERS! Is there one near you? Now press the "D" key. If an ast-
erisk (*) appears next to a callsign (hopefully that nearby WIDE), you
hear 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)
E. If you heard that WIDE station directly, enter it's callsign and its
ssid, if any. Follow this with a comma, then type in "WIDE". For exam-
ple: "N2MH-15,WIDE" would be how I might enter it here in The Bronx, but
the nearest WIDE to YOU is what YOU'RE looking for.
Next you want to set your Power-Height-Gain figures. Press I(nput)
M)y) P(ower) and tell it how many watts you're using, the elevation of
your antenna above AVERAGE terrain (look at a topographical map of your
area,) it's gain in dBd and the antenna's directional pattern in degrees
or 0 (zero)for an omnidirectional antenna.
Finally, set your Status Text by pressing I(nput) M(y) S(tatus) and
typing in a short comment, different than what you used in your Position
Text earlier. At this point, you're about as far as you need to go for
now.
+----------------------------------------------------------------------+
|Arte Booten <n2zrc@arrl.net> AEC for Digital Services, NYC ARES/RACES|
+----------------------------------------------------------------------+
David S. Dobbins Amateur Radio: K7GPS
POB 217 http://www.nwaprs.org
Pe Ell, WA 98572 http://map.findu.com/k7gps-9
(360) 291-3707
APRS: Using It
(or: Now that I've got it set up, how do I make it work for me?)
by Arte Booten, N2ZRC <n2zrc@arrl.net>
In other articles I've described what The Automatic Position Repor-
ting 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 all of these
stations appearing on my screen. Now what do I do?"
One feature in APRS is the ability to send what we call one-liners;
that is, one-line messages from station to station either direct, or via
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 if
they got it when you receive an *ACK* which replaces the first five cha-
racters 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 the station you're
trying to send to is someplace else, you can STILL send it there (if us-
ing APRSDos or pocketAPRS) by specifying any of several alternate digi-
peater paths which the program can store for you. If you press O(pera-
tions) D(igipath) S(ave), you're prompted to enter a two-letter code for
that path via whatever path you choose, such as:
NJ VIA WB2ZII,N2MH-15,KB2EAR-1,K3ATI-11
to get to Southern New Jersey from Westchester. To see the 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 di-
rect and, sometimes, the only feasible path.
The weather systems feature of APRS allows you to see weather data
in real-time, transmitted by stations with using several different kinds
of autometed weather stations, including those made by Peet Bro's, Davis
Instruments and Oregon Scientific (which made the Radio Shack unit).
Depending on which options the weather station owner installed, 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. Press W(eather) to
see a list of options to choose from.
If at any time you wish to cease transmitting without shutting down
the program, simply touch C(ommands) X(mit). This toggles the TX timer
within APRS. You will still send out whatever the TNC itself is set to
transmit at their predetermined periods. When you want to send a spe-
cific packet (usually your position), you can do so by pressing X(mit)
P(osition) [or S(tatus), M(essage), S(tatus), O(bject) or A(ll), as the
case may be.]
In order to find a station on the screen, use O(perations) F(ind)
(what else!) command. If you'd like to see something really neat, try
O(perations) R(eplay) with a mobile station. You'll see that 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) you'd use
O(perations) Q(uery), followed by a radius in miles from you.
Now that you've been QRV with APRS for a few hours, you don't par-
ticularly 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> <cr>, it asks if you want to save a
backup (it'll do so by default). Next time you fire it up, you'd press
F(iles) L(oad), then type BACKUP.BK . Every time you shut APRS down, it
saves this file, replacing the previous copy. Be aware, though, that
all of those packets are timed, and any station 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 bear in mind when playing APRS is that the best way to
learn, as with anything else, is by doing. You can use most of the com-
mands 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 rare. Usually
the three-fingered-salute (Ctrl-Alt-Del) will get you out of it and you
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 just
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 ev-
ery so often, 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 push-
es 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.
I hope you've enjoyed this series about 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 ques-
questions of any station on the air at that time. We're all very excit-
ed 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! 73
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
FIGURING OUT THE BEST DIGIPEATER PATH FOR APRS PACKETS
(or, Which Way Do They Go, George?)
by Arte Booten, N2ZRC <n2zrc@weca.org>
As with any packet networking, path selection depends on what can be
heard by you and those that can actually hear you. You can get the
equivalent of an MHEARD command, showing you the paths stations near you
are using and which stations you hear direct by pressing the D(igipeat)
key. See who these are. Hopefully, one of them will be a WIDE.
Any APRS network relies on the majority of fixed stations having
their TNC's DIGIpeat function turned on and their MYAlias set to RELAY.
Since APRS is an unconnected protocol, packet nodes (with a few excep-
tions), which rely on connections and error-checking for data transfer,
are counterproductive. APRS utilizes that DIGIpeat function by the use
of GENERIC callsigns as a TNC's alias(es), most commonly RELAY and WIDE.
There are various flavors of WIDE, all represented differently on
the screens of different APRS versions. But first let me describe the
function of RELAY in the APRS network, as this is a useful, but often
misused, generic callsign. RELAY stations generally consist of your
average "Joe Aperze" in order to allow low-power, low gain mobile and
portable stations into the network. In many areas, most of these RELAYs
are able to hit the nearest WIDE directly.
This means that if you can hear and get digi'd by the nearest WIDE
from a fixed location with reasonable consistency, you should AVOID THE
USE OF RELAY because if a WIDE hears you, others probably can as well..
and they're probably also using the alias RELAY. This causes collisions
as each of the RELAYs that hear you try to digipeat your packet at about
the same instant. And your packet will probably die then and there.
Now back to the various flavors of WIDE. The first is just that.
It'll digipeat anything that specifically goes via its callsign as well
as to the generic callsign WIDE, shown as a small green star in APRSDos.
Sometimes, there's also a weather station associated with this DIGI, in
which case APRSDos shows them as a green circle. Next comes WIDE-RELAY.
These are TNC's that can have two aliases and digi packets addressed via
RELAY, WIDE or its own callsign and show on APRSDos as big green stars.
We also use WIDEs that use an alias of TRACE. Their firmware sup-
ports the DIGI-SWAP function. When it DIGIs something addressed via
one of its generic callsigns it changes that GENERIC callsign to that of
its own in the VIA: field of that packet. This allows people to see how
the network is propagating and makes selection of paths a bit easier.
Those of us running APRSDos, WinMacAPRS and pocketAPRS see these as that
large star with a T in the middle.
The next type uses something the inventor of APRS (The Great Oracle
of Glen Burnie) Bob Bruninga, WB4APR, first proposed several years ago
to enhance unconnected networking via amateur packet radio and Kantro-
nics recently picked up on. It uses a scheme Bob calls WIDEn-n. "N" is
a number between 1 & 6. The first of these would represent the number
of "hops" you want to take.
The second of these numbers depends on how many times that packet
has been digipeated by the time the last digi retransmitted it. It's
set by the firmware in current Kantronics TNC's (but I understand that
others *MAY* be coming out with it in the "near" future) and decrements
one from that number on the packet it's heard, but hasn't yet DIGI'd.
WIDEn-n TNC's can also be set for callsign substitution, as I described
above. They have an N in the middle of the green star.
The beauty of WIDEn-n is seen best in a network in which most,
if not all, WIDEs in a given area have such firmware. In others, users
of callsign substitution might consider shutting that feature off. Un-
fortunately, not everybody that has a digi is USING Kantronics' stuff.
And some of those that are aren't willing or able to change the chip.
This pretty much describes the APRS network in my part of the woods.
What's the best path? Look around. Who hears you. Who do they
hear. And where do you want the packets to go? I suppose you'd like
a nice, stable path from Montauk to Albany and Newark to Binghampton.
Good luck. The path you need is there, if you can see anybody else on
your screen. If a Green Star can hear you, then that's gonna be your
starting point. From there, just follow the bouncing green stars. 73
***
From : KK5WM
To : N5VLZ
Type/status : PN
Date/time : 16-Sep 21:44
BID (MID) : 493_KJ5SF
Message # : 6224
Title : APRS
(This message has been read 1 times so far in this BBS.)
Path: !KD5AYE!KJ5SF!
Hello, Daryl...been a LONG time since we've talked (I used to be KC5ILA)!
Sorry it took so long to reply to your message...my tnc and radio have been
on the APRS frequency for some time and I've forgetten to check my packet
mailbox!
You don't need much to run APRS with, depending on what you want to do.
Just about any TNC that can act as a digipeater can act as an APRS RELAY
node (short-range)...doesn't have to be hooked up to a computer for that.
Newer firmwares for many TNC directly support APRS and GPS messages...the
LTROCK node on Shinall Mt. (I never know if I spell that right :)) is a
standalone node which doesn't have to use a computer to handle the more
sophisticated APRS digi'ing.
There is also software available for DOS and Linux that can turn almost in
TNC into a full-feature APRS digipeater, but of course require a computer.
As far as personal use goes, you can use a PC running APRS software to do
anything from just displaying the location of the various APRS stations it
receives either off the air or the internet, to being an APRS internet
server. You can also send messages to specific stations, internet e-mail
(SHORT messages!), ICQ messages (not two-way, tho) and weather information.
Also, you can hook up a GPS unit, a TNC or other available interface, and
a radio and go mobile. That is the main use of APRS. There are also many
APRS weather stations around the country (and world, for that matter)
which broadcast weather info for their location. A few stations send out
satellite position info.
As far as the technical side of it: The national APRS frequency is
144.390Mhz, simplex, using the AX.25 packet radio protocol. Everything
is sent as UI packets (unconnected), so there is no guaranteed
error-correction or message confirmation, although the APRS messaging
protocol does send acknowledgement packets back to the sender. There is
software available for DOS, Windows, Macintosh and Linux.
We are just really getting started with APRS here in Central Arkansas.
Bill (KC5ECB) was at our field day site and the APRS demo station we had
sparked his interest, so he bought the equipment to put a WIDE-area APRS
node in Little Rock. It's callsign is LTROCK. There are a few users
so far...myself, Bill, Tim Grooms in Mayflower (K5TLG) and Jamie Hutches
in Searcy (KD5GOB). Jamie and I operate a couple of nodes in our area
(I'm in Beebe). Mine is a RELAY node and is not permanently on the air
yet. Jamie runs a WIDE node (N5HU) and an IGate (KD5GOB, Internet Gateway)
in Searcy at Harding Univ. We're searching for good locations to place a
few more WIDE nodes around the Cen. AR area...they need to be a decent
distance apart to reduce contention.
Software to look for: WinAPRS, UI-View, APRS/dosAPRS, APRS+ (Windows),
MaxAPRS. The linux X-APRS is still under development. A good web site
for APRS info is www.tapr.org, as well as www.aprs.net, www.aprshelp.com
(Scott Ratchford's site) and I think www.aprs.org. WB4APR--Bob
Bruninga--is the developer of the protocol and is very active in its
continuing development. Either aprs.net or aprs.org is his site at a
Navy facility near Wash. DC. www.findu.com allows you to map people's
locations view the web (and is the location of the current main APRS
internet server).
I better quit before I fill up a tnc buffer! Long-winded, I know, but
it's pretty interesting. If you have more questions, send a note via
packet or email: kk5wm@ipa.net. I promise to check my packet mail more
often :)
73,
james
=== End of messsage #6224 to N5VLZ from KK5WM ---
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