Digital Modes

Digital Modes are another method of using amateur radio. These modes work on the concept of a MODEM (modulator/demodulator). MODEMS work by taking digital data and modulating it into analog audio sounds, which are then transmitted over a radio. A MODEM on the other side demodulates the received audio and converts it to digital data suitable for reading by a computer. An operator can get into digital modes by having a computer program produce the appropriate sounds out of their speaker and play it into a radio’s microphone, as well as having the radio’s speaker play into the computer’s microphone. This is known as acoustic coupling.

Two common programs for real time digital modes are:

Acoustic coupling is a free way to get started, but is both noisy to the environment and impacted by the environment itself. To improve on this, we recommend a radio to computer sound interface.

  • SignaLink USB – connects via USB to your PC, presents a new sound card, and they provide lots of interface cables for different radios. It also provides PTT control.
  • MFJ-1275 – this works using an existing sound card and serial port, along with getting a cable to connect to your radio.

APRS or Amateur Packet Radio System is a digital PACKET (AX.25) mode for amateur radio. It is designed to provide real time information about amateur radio resources, such as operators, repeaters, events, command posts, hospitals, etc. Operators equipped with APRS can send bulletins, text messages, emails, weather information, or their GPS coordinates over amateur radio frequencies. This can be received by all other APRS equipped operators on the same frequency within range. There are also digipeaters that implement a store-and-forward method to further repeat APRS information outwards. Many digipeaters also provide what is known as i-gate functionality. An i-gate can forward APRS packets from the RF side to Internet based APRS servers. Some i-gates also will forward traffic from the Internet side out to RF.

  •  To view APRS stations on a worldwide online map.
  • Direwolf – A text based, cross-platform APRS digipeater/igate application.
  • APRSISCE/32 – A nice, modern windows based (or Linux/Wine) APRS Client.
  • YAAC – Yet Another APRS Client. Their website is not much to look at, but this cross-platform APRS client with offline maps is really nice.
  • APRSDroid – This is *the* client to use for Android APRS. It can view Internet APRS, or connect to your radio using audio cables or bluetooth.
  • Mobilinkd TNC2 – This is a bluetooth “terminal node controller” that connector a radio using cables, and then to a PC or Android phone using bluetooth. This is an excellent device.

APRS Capable Radios

  • Kenwood TM-D710GA – mobile 2m/440 radio with GPS and TNC built in. This radio can operate as an APRS station and as a fill in digipeater. It is also easy to connect to a standard computer serial port.
  • Kenwood TH-D72A – Dual band handheld with GPS and TNC built in. As last year’s model, this is a cost effective way to get into handheld APRS. This device will connect to a PC using USB and show up as a serial port.
  • Kenwood TH-D74A – Newer model of the D72A, includes 220Mhz band and D-star. Like the D72A, it connects to a PC via USB, but also provides bluetooth connectivity as well, making it easier to connect to mobile devices.
  • Yaesu VX-8DR – Yaesu has several APRS/GPS handhelds in the VX-8* range.