Morgantown APRS

What is APRS

Automatic Packet Reporting System (APRS) is an amateur radio-based system for real time digital communications of information of immediate value in the local area.[1] Data can include object Global Positioning System (GPS) coordinates, weather station telemetry, text messages, announcements, queries, and other telemetry. APRS data can be displayed on a map, which can show stations, objects, tracks of moving objects, weather stations, search and rescue data, and direction finding data.

APRS data are typically transmitted on a single shared frequency (depending on country) to be repeated locally by area relay stations (digipeaters) for widespread local consumption. In addition, all such data are typically ingested into the APRS Internet System (APRS-IS) via an Internet-connected receiver (IGate) and distributed globally for ubiquitous and immediate access.[2] Data shared via radio or Internet are collected by all users and can be combined with external map data to build a shared live view.

APRS has been developed since the late 1980s by Bob Bruninga, call sign WB4APR, currently a senior research engineer at the United States Naval Academy. He still maintains the main APRS Web site. The initialism “APRS” was derived from his call sign.

APRS Stations and types in and around Morgantown

Morgantown: DigiPeater-Raspberry Pi running Direwolf. Connected to an Alinco DR-135 MKIII. System Admin: Dean Thompson (KD8YNY).

Morgantown: I-Gate-PyMultimonAPRS iGate. RX Only, unsure of receiver. System Admin: Stephen Devience (N8URE).

Cheat Lake: DigiPeater-Raspberry Pi running Direwolf. Unsure of radio type. System Admin: Spencer Graham (WT8WV).

Bruceton Mills: Digipeater-Raspberry Pi running Direwolf. Unsure of radio type. System Admin: Josh Prichard (KC8TAI).

APRS Frequency

North America uses 144.390 MHz, tuning to this you will hear from time to time APRS data being transmitted. It is a data stream of 1200 baud rate on VHF, there is no error correction. Other frequencies can have a higher baud, but generally the 1200 baud is used on VHF systems.

Can I build one?

You sure can, all you need is a Raspberry Pi, a small cheap USB sound card, an unused radio that you can modify slightly and internet connection in most cases. The reason I used the Alinco DR-135 MKIII is due to the 9 pin D connector on the back, it is already configured to allow Audio to pass in both directions, has the ability to key the radio and a host of other connections. The radio from new comes with a built in TNC, I chose not to use the TNC as I went with the Pi and Direwolf which acts as a TNC.

Some knowledge of Linux is helpful, but if you get stuck, I am sure one of us can help you out with it.

Documentation to follow can be found here https://github.com/wb2osz/direwolf/blob/master/doc/Raspberry-Pi-APRS.pdf

Things to consider

APRS DigiPeaters can get over populated in areas, try to coordinate with other admins in your area, APRS transmits and receives on one frequency (Simplex) and can be easy for stations to step on one another. This in turn could mean lost packets to the RX stations.

RX only or Igates help fill the areas where there are dead spots, these are highly encouraged even in populated areas. Tune your radio to 144.390 and listen for about 10 to 20 minutes, depending on traffic, you probably will hear data within less than a minute. If you hear nothing within 20 minutes consider building a digipeater for your location, if you hear traffic it could be a passing vehicle, keep listening.. If you continue to hear the data, consider building an iGate or have a look on APRS.FI and see what Gateways are near you before overpopulating the frequency with more traffic.