Glossary

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APRS Glossary

A

  • Announcement - An APRS message that is repeated a few times an hour, perhaps for several days.
  • APRS - Automated Packet Reporting System
  • APRS Data - The data that follows the APRS Data Type Identifier in the AX.25 Information field and precedes the APRS Data Extension.
  • APRS Data Extension - A 7-byte extension to APRS Data. The Data Extension includes one of Course/Speed, Wind Direction/Wind Speed, Station Power/Antenna Effective Height/Gain/Directivity, Pre-Calculated Radio Range, DF Signal Strength/Effective Antenna Height/Gain, Area Object Descriptor.
  • APRS Digipeater Path - A digipeater path via repeaters with RELAY, WIDE and related aliases. Used in Mic-E compressed location format.
  • APRS Data Type Identifier - The single-byte identifier that specifies what kind of APRS information is contained in the AX.25 Information field.
  • APRS-IS - APRS-Internet System
  • Area Object - A user-defined graphic object (circle, ellipse, triangle, box and line).

D

  • digi - short for "digipeater"
  • digipeater - a "digital repeater," a radio transceiver (often mounted on a hill or mountain) which re-broadcasts the packets it receives over a wide area

B

  • Base 91 - Number base used to ensure that numeric values are transmitted as printable ASCII characters. To obtain the character string corresponding to a numeric value, divide the value progressively by decreasing powers of 91, and add 33 decimal to the result at each step. Printable characters are in the range !..{. Used in compressed lat/long and altitude computation.
  • Bulletin - An APRS message that is repeated several times an hour, for a small number of hours. A General Bulletin is addressed to no-one in particular. A Group Bulletin is addressed to a named group (e.g. WX).
  • Bulletin Identifier - A single digit 0-9 that identifies a particular bulletin.

F

  • findu - a web site at http://www.findu.com which collects APRS data from APRS-IS and can answer queries on the database. Also, generically, the Internet aspect of APRS, though there are many other useful APRS sites

G

  • gate - short for IGate
  • GPS - Global Positioning System. A //GPS receiver// uses signals from satellites to determine its position. For APRS use, the GPS receiver will then send the location information to a TNC for transmission by radio

H

  • ham - a person who uses amateur radio. The origin of the nickname is obscure
  • hop - when a digipeater repeats a packet, it's considered a "hop." If a second digi receives the packet from the first digi and retransmits it, that counts as a second hop

I

  • IGate - Internet Gateway, a radio and computer setup for receiving packet data via radio and sending those packets to the Internet (via APRS-IS)

P

  • packet - a bundle of data (like an APRS user's call sign and location, or a weather station's report on conditions) plus a path and other information, represented as a set of bytes in a computer or transmitted via radio as a series of rapidly-changing tones
  • path - a specification of the path a packet should take through the digipeater system. Can be explicit (using the callsigns of the intended repeaters and the ultimate destination) or symbolic, like "WIDE2-2" which digipeaters will interpret to mean "repeat twice."

T

  • TNC - Terminal Node Controller. A device which can control a radio and transmit computer data (like a user's call sign and GPS position information) using a series of rapidly-changing tones

V

  • Voice Alert - is a way of setting up an APRS station to notify you if other active stations come into simplex voice range
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