Digital Modes: D-Star Digital Radio
Most of this Information here was gleaned from various websites that either discussed D-Star or the various protocols involved in its creation. A good starting place for the original information is the Icom website at: D-Star Digital Radio
In its most basic form a D-Star repeater would function almost exactly the same as the analog repeaters we are used to using today. There are a few notable exceptions:
You won't hear "partial quieting" signals, picket fencing or fading. The signal will either be there 100% quiet or not at all.
You won't have a squelch control. This function is unnecessary in the digital world.
You won't use PL tones. Receivers look for embedded callsigns, not low frequency tones.
If the system consisted of only a hilltop repeater and a small number of handhelds and mobiles scattered about, you would only be able to communicate with each other. An outsider passing through could join in only if he was equipped with a D-Star radio.
You could also send and receive low speed packet signals including GPS/APRS among the group.
But, once the system was "built out" to the D-Star architecture, some interesting features become available pretty quickly.
The connection to the internet "networks" the system to all the other D-Star systems out there. Right now there aren't a bunch of them but there are a number and the number is growing, primarily in the US, the UK and Japan.
The addition of a High Speed Data Module at the repeater site enables data to be sent and received at the rate of 128 kbps. This is equivalent to the uplink speed of a conventional DSL signal.
There are some misconceptions about the D-Star system and one of the most often heard is that it's nothing but another IRLP system. One can see where that comparison might be made since in functionality, it does work in a similar manner. A D-Star user can communicate with other D-Star users in the same "zone" just as easily as in a "zone" across the country or half a world away. The linking is seamless because unlike IRLP, no external computer is required (it's built in to the D-Star system) and no control tones are required. Since all connections are at the user level rather than at the system level, all one needs to do is enter the desired callsign into the radio and the link is established on the first PTT.
The High Speed Data capability also permits some internet-like features such as email and remote control. You will hear some criticism about this functionality as well. Many hams still believe in a complete separation of radio and Ethernet. Both the High Speed and Low Speed data capability become highly attractive to EMCOMM supporters however.
Another misconception often heard is that adoption of D-Star locks one into the Icom product line. As you know radio owners are like car owners in some respects. You've got Ford people and you've got Chevy people and they don't often switch. While it is true that at the present time D-Star is made only by Icom, the architecture and design detail is not proprietary and any other manufacture is welcome to begin producing D-Star-like equipment although the name will probably be different. The development work up until now has been funded by the Japanese government with cooperation by the JARL and Icom, but lots of other people have contributed to the effort. As far back as 1980 the TAPR organization did significant work on the AMBE codec used by D-Star. It won't be long before experimenters will be contributing home-brew articles to QST.
Probably the main reason that other manufacturers aren't rushing to make digital equipment is the same reason that Hams are not rushing to buy digital radios. Interest will grow as others (the early adopters) get equipment on line and start talking about it.
The Radios
Browsing the new AES catalog I find 3 mobiles and 4 handhelds that are either D-Star now or upgradeable. The IC-91A for example replaces the IC-W32 and can be upgraded to D-Star (becoming a IC-91AD) by opening it up and slipping in a UT-121($200.00). The D-Star line will also operate on the analog channels; as a matter of fact, I downloaded the manual for the ID-800 ($609.99, D-Star ready) and they never got around to talking about Digital Operation until page 60 of 132. Easy to read? No! Typical Icom documentation.