APRS

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APRS is one of several amateur radio digital modes specialized for position telemetry from a GPS.

  • Automatic Packet Reporting System (historical name)
  • Automatic Position reporting system

APRS is similar to packet radio in that it also uses the AX.25 protocol layer, but uses a different routing scheme and does not have a concept of connections or sessions.

On VHF, APRS in the US mostly uses the frequency 144.390, although any of several frequencies can be used that are reserved for digital modes by the local frequency coordinator. World wide, other frequencies are used. Many HF frequencies are also used for APRS.

Uses for APRS[edit]

  • Instant messaging type communication over radio.
  • Tracking (with GPS) of people, vehicles, storms, objects, etc.
  • Weather station information
  • GPS as well as other Telemetry
  • Coordinated radio direction finding via fade circle search using omnidirectional antennas on mobile and stationary stations
  • long distance trip coordination and communication
  • DX cluster and other localized information sharing
  • satellite communication

Components in an APRS system[edit]

  1. Radio
  2. TNC (packet radio modem) (may also need rigblaster or equivalent)
  3. computer
    • display incoming data
    • allow user to send messages
    • convert GPS data to beacon packets
    • (when supported) convert incoming station locations to GPS waypoints
  4. optional GPS

Software available[edit]

Radios that directly support APRS[edit]

Almost all ham radios can be used with APRS, but these have it built in:

  • Kenwood TM-D700 moble/base station radio
  • Kenwood TM-D710 moble/base station radio
  • Kenwood TM-D7A handheld
  • Yaesu VX-8R handheld
  • Yaesu FTM-350E
  • Garmin Rhino (includes GPS, PDA, uses FRS not amateur radio unless modified)
  • Byonics has several kit radios and radio modems

TNC[edit]

If you do not use a software TNC or a radio that includes a TNC, an external TNC will be needed. See Choosing a TNC for APRS for a more complete discussion including a list of reviewed products. Unfortunately, most lists like this were written 10 or 15 years ago and never updated. They contain mostly broken links to discontinued products, from the previous Century, and companies that don't exist anymore. Potential criteria for selecting a TNC might include:

  • Will it be used for HF use?
  • Do you need 9600 baud, PSK, or other digital modes?
  • Will you use it with a (serial port starved) laptop?
  • Do you want to use it for tracking standalone with a GPS and without a computer? (Would a tinytrack be good enough?)
  • Will you use it for packet radio? (I.e., do you need a full TNC or is KISS mode enough?)
  • Will it be used for a digipeater? (need remote control options)

Costs:

  • $36 for a kit from tinytrack (transmit only, no computer interface)
  • ~$100 - $300 for a commercial full TNC
  • ~$400 for a DSP based TNC
  • ~$500 for a Kenwood D700A mobile radio (dual receive xband aprs 50/35W xmit)
  • ~$350 for a Kenwood TM-V7A hand held radio (dual receive xband aprs 5W xmit)
  • http://www.argentdata.com/catalog/

Software TNC's are becoming increasingly popular because you can get better performance and more features at much lower cost.

Slide Show covering origins of Packet Radio and evolution to using Software TNCs rather than 1980's style hardware.

GPS[edit]

Features to consider when selecting a GPS:

  • Integrated with a PDA?
  • Includes an LCD screen and maps?
  • Detachable / external antenna?
  • Small form factor?
  • RS232 serial or USB? (some have both)
  • Protocol format?
  • NEMA or proprietary (Rockwell?) format? (Most APRS software wants NEMA.)
  • Does it support WAAS?
  • If it has a map display and NEMA, does it also support NEMA in to display waypoints from the APRS software?

Costs:

  • $15 + $25 antenna at hamcation (motorolla, no case)
  • $80 basic GPS with display (ex: Garmin e-trex, GPS-18PC)
  • ~$300 - $600 Garmin Street Pilot

A few GPS manufacturers:

sound card interfaces[edit]

If you want to connect the radio directly to the computer without a TNC and use a software TNC, then circuitry is needed to convert radio audio output to soundcard level input, and soundcard output to radio microphone input. Some soundcards have adjustments that can convert some of the levels. Most soundcards will need a level converter interface to help. Some radios also have outputs that are suitable to connect directly to the sound card.

Considerations when choosing a sound card interface:

  • kit form or assembled?
  • Is PTT control needed too?
  • Is an additional external microphone also needed? (for echolink use)

windows tool chain[edit]

External links[edit]

APRS access on internet

Additional information

digipeater / igate info[edit]

vendors[edit]

Retrieved from "http://newton.i2lab.ucf.edu/w/index.php?title=APRS&oldid=15080"