D-STAR (Digital Smart Technologies for Amateur Radio) is a digital voice and data protocol specification for amateur radio. The system was developed in the late 1990s by the Japan Amateur Radio League and uses minimum-shift keying in its packet-based standard. There are other digital modes that have been adapted for use by amateurs, but D-STAR was the first that was designed specifically for amateur radio.
Several advantages of using digital voice modes are that it uses less bandwidth than older analog voice modes such as amplitude modulation and frequency modulation. The quality of the data received is also better than an analog signal at the same signal strength, as long as the signal is above a minimum threshold and as long as there is no multipath propagation.
D-STAR compatible radios are available for HF, VHF, UHF, and microwave amateur radio bands. In addition to the over-the-air protocol, D-STAR also provides specifications for network connectivity, enabling D-STAR radios to be connected to the Internet or other networks, allowing streams of voice or packet data to be routed via amateur radio.
In 1998 an investigation into finding a new way of bringing digital technology to amateur radio was started. The process was funded by a ministry of the Japanese government, then called the Ministry of Posts and Telecommunications, and administered by the Japan Amateur Radio League. In 2001, D-STAR was published as the result of the research.
In September 2003 Icom named Matt Yellen, KB7TSE (now K7DN), to lead its US D-STAR development program.
Starting in April 2004 Icom began releasing new “D-STAR optional” hardware. The first to be released commercially, was a 2-meter mobile unit designated IC-2200H. Icom followed up with 2 meter and 440 MHz handheld transceivers the next year. However, the yet to be released UT-118 add-on card was required for these radios to operate in D-STAR mode. Eventually, the card became available and once installed into the radios, it provided D-STAR connectivity. The June 2005 edition of the ARRL’s QST magazine reviewed the Icom IC-V82.
JARL released some changes to the existing D-STAR standard in late 2004. Icom, aware that the changes were coming, delayed the release of their hardware in anticipation of the changes.
The Icom ID-1 1.2 GHz mobile radio was released in late 2004. The ID-1 was the first D-STAR radio that provided digital data (DD) mode operation. In this mode, data can be transferred at 128 kbit/s as a wireless bridge via the RJ-45 Ethernet jack on the radios. It was the only radio to provide this function until the release of the IC-9700 in 2019.
The first D-STAR satellite QSO occurred between Michael, N3UC, FM-18 in Haymarket, Virginia and Robin, AA4RC, EM-73 in Atlanta, Georgia while working AMSAT’s AO-27 microsatellite (Miniaturized satellite) in 2007. The two experienced minor difficulty with doppler shift during the QSO.
As of late 2009, there are around 10,800 D-STAR users talking through D-STAR repeaters with Internet connectivity via the G2 Gateway. There are approximately 550 G2 enabled repeaters now active. Note, these numbers do not include users with D-STAR capabilities that are not within range of a repeater, or working through D-STAR repeaters that do not have Internet connectivity.
The first D-STAR capable microsatellite was launched in early 2016. OUFTI-1 is a CubeSat built by Belgian students at the University of Liège and I.S.I.L (Haute École de la Province de Liège). The name is an acronym for Orbital Utility For Telecommunication Innovation. The goal of the project is to develop expertise in various aspects of satellite design and operation. The satellite weighs just 1 kilogram and utilizes a UHF uplink and a VHF downlink.
In 2015, FlexRadio Systems added D-STAR support to their line of HF transceivers and receivers via a software upgrade. D-STAR support requires the addition of the ThumbDV device from NW Digital Radio.
The system today is capable of linking repeaters together locally and through the Internet utilizing callsigns for routing of traffic. Servers are linked via TCP/IP utilizing proprietary “gateway” software, available from Icom. This allows amateur radio operators to talk to any other amateurs participating in a particular gateway “trust” environment. The current master gateway in the United States is operated by the K5TIT group in Texas, who were the first to install a D-STAR repeater system in the U.S.
D-STAR transfers both voice and data via digital encoding over the 2 m (VHF), 70 cm (UHF), and 23 cm (1.2 GHz) amateur radio bands. There is also an interlinking radio system for creating links between systems in a local area on 10 GHz, which is valuable to allow emergency communications oriented networks to continue to link in the event of internet access failure or overload.
Within the D-STAR Digital Voice protocol standards (DV), voice audio is encoded as a 3600 bit/s data stream using proprietary AMBE encoding, with 1200 bit/s FEC, leaving 1200 bit/s for an additional data “path” between radios utilizing DV mode. On air bit rates for DV mode are 4800 bit/s over the 2 m, 70 cm and 23 cm bands.
In addition to digital voice mode (DV), a Digital Data (DD) mode can be sent at 128 kbit/s only on the 23 cm band. A higher-rate data protocol, currently believed to be much like ATM, is used in the 10 GHz “link” radios for site-to-site links.
Radios providing DV data service within the low-speed voice protocol variant typically use an RS-232 or USB connection for low speed data (1200 bit/s), while the Icom ID-1 and IC-9700 radios offer a standard Ethernet connection for high speed (128 kbit/s) connections on the 23 cm band. This allows easy interfacing with computer equipment.