Latest update: 04/14/07
There are many items to consider as you begin to work with APRS. Not the least of which is what computer you will use. If you are going to run a desktop then you are probably limited to running from your house and probably being a weather station or, if you have no other WIDE coverage area digipeaters within 20 to 50 or so miles, a WIDE Digi. (See digipeaters below before you even consider this). If you are going to run a laptop computer then you have maximum latitude in what you do.
The minimum recommendation is a Pentium I at 200 Mhz. You will find that to be the slowest most people will tolerate for interactive map work. If you have something in the Pentium II or above, it will make your experience much more pleasant. With that said, many people can run a weather station quite well with a smaller computer engine.
The next main option you will want to think about is if the computer has a full function sound card. Without that you must run a Packet TNC. If you decide to run a TNC, you then need to think about how close to total functionality you want. Many TNCs will work in APRS, but the Kantronics KPC-3+ is the fullest featured (at $160 it durned well should be).
The Second half of the TNC decision involves the ability of the TNC to run in KISS mode. If yours will, then the software you choose can be much more versatile. You say "What does this buy me?". In simple terms, it allows much of the work from the TNC to be done in your computer. Thus if you were to want to run both a weather station and mobile locator on the same TNC, with KISS mode this would be easy. Multiple applications can "share" the TNC when in KISS mode.
Above all, if you buy a new (at least to you) TNC to use for APRS, bring it up under Packet first. This will minimize the confusion and problems you will have. Many bald men started will a full head of hair but decided to do APRS with an untried TNC.
While you are thinking about what you will put together, you can actually get a fixed APRS station on the air without a GPS and without standard APRS software. Berry, N0OYM, has a solution.
APRS software takes many forms. Major considerations are:
Another option is the - just announced - "Pocket Tracker" from BYONICS. This unit requires an outboard GPS and nothing else! It is a low powered (no spec's out yet but it claims 100 hours of operation from a 9V battery) encoder and transmitter that fits in al Altoids can. GPS, Altoids can with rubber duck - rock and roll!
Both of these are also available along with lots of other ham software for linux from http://radio.linux.org.au/ (You will probably need the packages ax25-apps, ax25-config, ax-25tools which are available from this site.)
If you have an older PC with a soundcard then soundmodem, aprsdigi and xastir make a good setup. It takes more effort to get it all going. But it can all be had for free.
Note: This code works with *MOST* operating systems and is compatable with maps used for UI-View! It also has direct interface with the D700. Thanks to Don, KC0QZR, for the information.
Map software, like APRS software, has many variations. The most popular seem to be DeLorme, Street Atlas, Rand McNally and Precision Mapping. The cost runs from free with a GPS (Rand McNally) to $50 for either DeLorme or Precision Mapping. Yet another option is the DeLorme topographical version that runs $100.
With the Rand McNally or DeLorme version you will need to generate maps that are specific to where you want to run. These maps will need to have an .INF file to describe to the software the Lat/Lon covered by that map.
The cleanest (and easiest on you) is to run UI-View APRS software with the PmapServ option and Precision Mapping software. This provides coverage of the entire United States with detail down to the one tenth mile resolution (one half the screen shows one tenth mile of land). Total cost of the entire package is about $66 (it varies with the current exchange rate of US Dollar to UK Pound for UI-View).
There are at least as many options in GPS as there are in any of the other considerations. They will run from as little as $82 to as much as $600. You DO want a GPS receiver with 12 or more channel receive capability. It takes three satellites to get lat. long. on your position and four if you want altitude. If you only have one channel then the GPS will have to establish contact with them ONE-AT-A-TIME (read that VERY slowly). The twelve channel units can have information from as many as twelve satellites going at once (I have seen units have three satellite lock in under fifteen seconds, where single channel units can easily take ten or twenty minutes).
A critical option is that the GPS output NMEA standard
data. Without that you are not able to talk to most
Garmin are top of the line, while Deluo are the least expensive yet seem to work.
Don't forget the interface cable. This comes standard with some units. You will need to look at the computer you will be running. Does your computer have USB connections?
The exception to this is if you are running a Kenwood D700 and are going to connect the GPS directly to the D700. You then get power directly from the D700 via the interface cable and use the internal TNC. In this case there is a DB9 connection on the D700 that goes to the computer (watch out for male/female pins on the cable - this is a more exotic cable than some stores have - I had to make mine from two standard cables - pl).
You will install your software per manufacturer / vendor instructions. There will invariably be a few items that will give you heart burn. Since I run UI-View I will share my experiences so that you will understand of what I speak.
Let me preface this with - Roger (UI-View author) did an EXCELLENT job with the software and instructions! But I did find a few little gotchas.
Initial setup of your installation will vary only in the specific commands that you issue and the manner in which you have to enter them (varies with the software you use). The functions you will have to use are:
You are now at the point where, if you are running UI-View, you hear a very British accent announcing each station as they beacon (this can easily be turned off once everything is running to your satisfaction). This is very comforting as you begin because as you look, once more, at the documentation you hear YOUR machine humming along and doing its thing. Find a friend, or make a new one, that has APRS going. They will be able to answer many questions and save you some frustration.
There are many items that many will not bother with and some will
wish they had (once they find out how easy it is). A few of these
(this section is under development):
This segment is under development and input and/or corrections are solicited!
Digipeating (name derived from - Digital Repeating) is the process whereby we extend the useful range of VHF/UHF communication within Packet. In APRS digipeating is your entry into the "network" of stations that function together to provide features that would otherwise be unavailable. There are several strong implications in that statement. Since you are going to function as part of an unconnected network (anyone can function within a connected network because the protocols enforce compliance) it is important that you understand the potential impact your station (in the form of your activity on the "channel") will have.
You can minimize your impact on the frequency by remembering just a few pointers. Let's start with how Packet and APRS differ so that we can better understand how to "be a good neighbor".
Once you look at the descriptions above you say "How do I talk to distant stations?". Easy. APRS uses "generic call" addressing (aliases). There are six aliases used by those doing APRS digipeating but only three are of use to us. They are "Relay", "Wide" and "Trace". Keep in mind that these are your primary "VIA" addresses. Well if there are only three, how can it be complicated? Let's look further:
Please NOTE: Both WIDE and TRACE can have an option of "n-n". A digipeater that supports "n-n" will digipeat any "n-n" packet that is "new" (to that digipeater) and will subtract 1 from the number to the right of the dash until that number reaches -0. The digipeater keeps a copy of the packet and will not digipeat that packet again within about the next twenty eight seconds. This considerably reduces the number of superfluous digipeats in high density areas.
You will set up your digipeat aliases as 1) Your call and 2) either Relay or Wide (depending on if you are mobile or fixed). Or worded differently:
You then set up your UNPROTO address to something like APRS,RELAY,WIDE or APRS,RELAY,WIDE3-3 (which replaces APRS,RELAY,WIDE,WIDE,WIDE) if you are mobile and reduces the digipeat duplication (see above on n-n). The character string "APRS" in the UNPROTO address is to maintain compatability with those pieces of software that use those characters to convey other information.
What does all this mean? You are probably going to have an UNPROTO of "APRS,RELAY,WIDE2-2" or "APRS,RELAY,WIDE3-3" (without quotes).
Spend some time in APRS and learn your local network before you turn on digipeat.
DigiPeating with a UI-View slant.
To the Amateur Radio Club in Texas that copied ALL of the material in this and linked pages, and call it their own, good luck. You have down level material. Pat Lambert W0IPL