Ham Radio APRS – The Complete Guide

APRS is a digital communication system used by amateur radio operators to send packets of data via radio waves to exchange messages and information over short distances. It was initially developed by Bob Bruninga, WB4APR (SK), in the 1990s, and has since become extensively used among amateur radio operators.

APRS works by transmitting digital packets of information, such as GPS coordinates, to other stations within range. The packets are then relayed to the APRS network, which consists of a series of Internet-linked gateways and digipeaters. In addition, the International Space Station operates an APRS digipeater which can be used to relay packets while overhead.

APRS has a wide range of applications, including tracking the location of vehicles, people, and weather stations. It is a well-known technology among hams, with numerous applications in emergency communications, tracking, and weather reporting. 

APRS is designed as a low-power consumption digital data link between amateur radio stations using RF on the 2-meter band upwards CW/USB channel with 4800 baud FM APRS with telemetry applications, SSTV frame stores, etc.

To set up APRS, there are different hardware and software options available. Some of the hardware includes a radio with built-in APRS capability, a computer with APRS software and a soundcard interface, or mobile phone software for Apple and Android devices. Here are the steps to follow:

1. Configure the radio: If your radio has APRS capability, you need to configure the software based on the instructions provided by the manufacturer. For radio and computer design, you need to install APRS software on your computer and create an audio interface between your PC and radio. For simple receiving, a cable connecting the radio’s audio output to the PC’s line input will do. Install one of the software versions mentioned above or one that fits your needs.

2. Set the frequency for packets: The frequency for packets should be set to 144.390 MHz in North America for the terrestrial network.

3. Configure the software: If your radio has APRS capability, ensure you have the path entered. This tells receiving stations how many times to digipeater your packet. WIDE2-2 is a typical setting. For radio and computer design, configure the APRS software to work with your radio by setting the frequency, baud rate, and audio levels. If you want your computer to send packet information it hears to the APRS-IS internet network, you can obtain a passcode for your callsign on the internet.

4. Configure the APRS software to use your GPS device to send your location: The radio with APRS capability should track your location as you move. For the static station, enter the location once in the software.

5. Test your setup: Transmit and receive APRS packets to ensure that everything is working properly. If you are near a station that sends APRS packets to the Internet, you can look at a site like https://aprs.fi/ to see if it was received by the terrestrial network.

6. Advanced: For radio and computer design, connect your PC’s output to the radio’s input to transmit your own packets. A tool like a “Rigblaster” can be purchased or home brewed.

APRS is a versatile technology that allows hams to exchange messages, track locations, and report weather conditions. By following these steps, you can set up APRS and start using it for your own purposes.

To use APRS, first set up the system and then start exchanging messages and tracking locations. APRS messages can be sent between stations or to the APRS network, which can then be displayed on a map in real time. APRS is commonly used to track the location of vehicles or people, such as hikers or search and rescue teams.

Weather data, such as temperature, pressure, and wind speed, can also be transmitted using weather stations connected to the APRS network.

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Just like with any other digital mode, APRS works on a single frequency at a time which you can see in the map above, but since most of the network is concentrated around 144.800 MHz in Europe and nearby countries you'll usually find it there or one of the nearby channels instead if something unusual was to happen in your area for example (covered more later).

Just remember that APRS doesn't have a dedicated channel so any ham radio operator may join in including mobiles which is why some repeaters (and even DMR services) are starting to carry this service over their analog FM carrier these days as well (search aprs.fi for such stations near you).

APRS has a variety of advanced features that can be used to enhance its functionality. One of the most useful features is automatic position reporting and tracking, which allows stations to transmit their location automatically at regular intervals. This is particularly useful for tracking moving vehicles, such as ambulances or delivery trucks.

Another useful feature of APRS is digipeating, which allows packets to be relayed from one station to another, extending the range of APRS. This feature is particularly useful in areas with limited coverage.

The International Space Station (ISS) has an active APRS digipeater thanks to the ARISS group. It operates on 145.825 MHz and uses unique PATH designators, so it is important to check before operating. A Kenwood TH-D74 can display a packet received from the ISS, which uses the call sign RS0ISS for its APRS radio.

APRS can also be used to report weather data, such as temperature, humidity, and wind speed. Weather stations can be connected to the APRS network to report weather data, which can be useful for monitoring weather conditions in remote locations.

Long Distance APRS is another advanced feature of APRS. Ambitious hams have events called “Golden Packet” where they attempt to send an APRS packet via simplex over long distances. The biggest event is the Appalachian Trail Golden Packet event in July. In this event, hams attempt to send a packet from one end of the Appalachian Trail to the other. The event uses a unique 2 Meter frequency (144.340) for the packets and a UHF channel for voice coordination.

Overall, APRS has many advanced features that can be used to enhance its functionality. These features make APRS a versatile and powerful tool for amateur radio operators.

So far, I've been mentioning AMTOR-A which is an obsolete protocol that requires either a separate terminal node controller (TNC) plugged into your computer or used as part of the modem itself. 

While most TNCs these days are USB based, some more expensive models featuring proper hardware encoders/decoders are still available however this mode of operation was quickly replaced by AX.25 packet networks running on VHF & UHF frequences thus bringing us to the question - does APRS require a tone?

The answer is no - it doesn't! Since both D-STAR and APRS use FM transmission over commercial frequencies, you can think of them both as wideband modes making them incompatible with older narrowband protocols such as AMTOR.

Although it does make APRS accessible to anyone using a standard handheld such as the excellent Yaesu FT-7800R, newer radios such as TYT MD-390 come with integrated packet support making them better candidates for APRS use.

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However, just like with AMTOR - some software might require you to set up a separate TNC and configure its parameters before enabling APRS over RF.

This usually means settings such as data speed, packets timeout and delay between retries on either side of the connection so keep your eyes open if you're planning on doing something more than casual messaging or even chatting 🙂 .

APRS is a popular local wireless protocol that uses 123 different codes to mark your current location and relay it to nearby users. These could be either automatically attached by APRS Messenger software based on the contents of the message you're sending or pre-defined manually before transmitting anything.