Xastir—Open-Source Client for the Automatic Packet Reporting System
First and foremost, sign up on the Xastir users mailing list (see Resources). Many helpful experienced users and quite a few of the developers hang out there. Posting requires a subscription, so sign up before you need it. Lurking and “dumb” questions are fine. Everybody learns or relearns a bit, and newbies are not harassed there.
Check the Xastir home page (see Resources), specifically the “XASTIR Documentation” and “Text docs distributed with Xastir” sections for useful documentation. Of course, look in the Xastir source main directory or the default install location of /usr/local/share/doc/xastir/ for the text docs as well.
Run Xastir for the first time, and it takes you to the File→Configure→Station dialog to enter your call sign and location and to choose a symbol that will appear on others' maps. Some symbols have special significance, so if you have a question, please ask on the list.
Visit the File→Configure→Defaults dialog next. Note that antenna height is not height above sea level (ASL), but height above average terrain (HAAT). Curt once lived at 150 feet ASL but –450 feet HAAT due to surrounding hills, but the protocol doesn't allow for negative HAAT; perhaps they figured no ham would live under such conditions!
If you have Internet connectivity, go to Map→Map Chooser, click on Online/Tigermap.geo, then click OK. If you're located in or near the US and zoomed in sufficiently, you should see Tigermap street maps appear shortly. If you don't have connectivity or are missing libraries to fetch maps, stick to built-in vector map formats like ESRI Shapefile. A map of the world in ESRI Shapefile format is included.
Hint: start Xastir from an xterm to catch error and warning messages. Also, check File→Configure→Timing→Internet Map Timeout to ensure it's adequate.
You probably will want to see other stations, weather alerts and the like. Go to Interface→Interface Control. Click Add, then Internet Server, then Add. You should see a new Internet Server entry on the Interface Control dialog. Click on that entry and then Properties. Enter server and port information into the form. Try rotate.aprs.net port 14580 with filter parameters of m/600, which causes reports for all stations within 600km to appear on the map. Enter a passcode to log in to the server, and see the callpass program that comes with Xastir. Send a position to the server if using the range filter, or the server won't know which stations to send you.
Run this script as root to fetch Shapefile maps for weather alerts:
For mouse functions, turn on emulate third button in your OS if you have a two-button mouse, as Xastir can use all three buttons of a three-button mouse. See the text docs distributed with Xastir for details on each function. Toggle buttons at the top of the screen change how the mouse buttons work, specifically Measure, Draw and Move. The cursor changes when in these modes to give visual verification. While we're at it, a few defines in xastir/src/main.c allow swapping mouse buttons and touchscreen operation, for those who aren't afraid to compile their own.
A few special keys include HOME (centers the map on your house or car), PageUp/PageDown (zoom keys), arrow keys (pan keys). Toggle buttons at the top of the screen provide most of these functions also.
The AX.25 protocol has multiple slots in the header of each packet for digipeater call signs, which APRS uses for a flooding protocol. One packet floods an area out to X digipeaters in all directions. Think of it as a time-to-live count or as a distance limit for each packet.
Currently accepted digipeater paths include WIDE2-2 or WIDE1-1,WIDE2-1 for home stations and WIDE1-1,WIDE2-1 for mobile stations. Either path will give you two hops outward in all possible directions. Never use WIDE1-1 as anything but the first digipeater call sign in the path; it triggers home station fill-in digis as well as mountain-top digis.
By following the above (currently only North American) recommendations, you can travel between RF networks without reconfiguring your tracker. High-altitude balloon or airplane-mobile trackers likely will need to reduce their paths to prevent interfering with many RF networks at once. Rocketry enthusiasts often run high packet rates on alternate frequencies due to their short flights (five or ten seconds); this avoids interference with the “normal” APRS network on 144.39MHz.
For “tin-foil hat” types, there are special path aliases for the end of your path to keep packets from being gated to the Internet: NOGATE and RFONLY. These are respected by most igate software.
Please stay abreast of the current national recommendations for your country—the above recommendations may not apply. If you're not part of the solution (and up to date), you're part of the problem, which definitely applies here!
Practical Task Scheduling Deployment
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
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