Dstar digital Radio

D-Star Digital Radio

by N6XN

For Things You Can Do


D-Star Digital Radio will be difficult to describe because it is different things to different people.  I won’t go into a lot of technical detail here so if you are interested in the “nuts-‘n-bolts” aspects, do a google search for dstar radio.

There are pros and cons.  First the pros, for the source itself: The Icom website for DStar Radio At this time, Icom is pretty much the only source for DStar radios although Kenwood is producing one that is available only in Japan.  The major manufacturers are certainly watching the growth of this mode and when it gets big enough you can be sure they will all be producing radios.

At the present time, the ICOM line is relatively expensive.  Some examples:  A dual band (144/440) mobile transceiver such as the IC2820H is currently selling for $650 less accessories.  This is a fine transceiver for both base station and mobile operation and in the basic configuration is pretty much limited to analog FM.  By installing a small daughter board (UT-123) it becomes a complete D-Star radio for both Analog FM and D-Star digital.  The UT-123 sells for $300.

For those wanting a Handheld radio, the IC-91A is available for $330.  The D-Star daughter board (UT-121) goes for another $200.  The IC-91A is a fine handheld and many ops use them as FM analog only.  This radio will soon be replaced by the IC92 which will be available with a built-in GPS / microphone. (note 1)  The believed price will be around $500 (D-Star ready) but the GPS microphone is expected to be additional cost.  You will find the entire line-up on the Icom website above.  Prices are available at http://aesham.com as well as numerous other Amateur Radio websites. More complete information on the IC-92 can be found at http://www.radioworld.ca

Here is another website that offers a couple of other viewpoints, not necessarily favorable:  http://technocrat.net/d/2006/4/5/2084

One of the big “bones of contention” is that D-Star systems use the internet as a means of interconnecting systems.  Here is the architecture in a nutshell:

A typical D-Star repeater consists of 4 modules.  The controller, a 1.2 gHz repeater, a 440 mHz repeater, and a 144 mHz repeater.  These 3 repeaters are referred to as the A-port through C-port respectively.  In it’s basic form a user can access the repeater using any of the Icom D-Star radios and talk to any other user on a D-Star radio within range of the repeater.  In this form, the internet plays no part.  If, however, either or both of the above users want to talk to someone on some other D-Star repeater anywhere in the world, they can do so by reconfiguring their radios to include the internet gateway.  This is often as simple as pressing a single button.  This is where the contention arises.  Many Hams feel that any system using the internet is not “real” radio.  Other systems using the internet such as Echolink or IRLP encounter the same prejudice.  Whether or not the internet belongs in Amateur radio is up to you to decide, not me.

Would you like to see who is using D-Star radio anywhere in the world, right now?  Take a look at http://dstarusers.org/dstar.php This is a nifty website that lists D-Star users by callsign in near real time.  If I should key my mic right now, (note 2) my callsign would appear on or near the top of that list within a few seconds.  Anyone seeing  this information would know my radio was active and could set his or her radio to call me from any other repeater.  This list is referred to as “The heard report” by regular users.
As I write this, there are 340 unique callsigns  on the list.  Not all of these folks are on the air right now, some are in bed, fast asleep.  You can pretty much judge who is available to talk to by the time stamp opposite their callsign.

Currently there are about 166 D-Star repeaters world-wide with more coming on line every day.  They are not only located in the US but in Australia, Austria, Brazil, Canada, England, Germany, Italy, Portugal, Switzerland, the Netherlands, and Trinidad/Tobago.  In the US, most of the repeaters are located in California, Texas, and the Southeast.  There are 31 states represented in all.  For a complete list, click on the repeater directory link on the left side of the “heard report”.

Why Digital Radio?

D-Star has several advantages over analog repeaters.

First, it uses less bandwidth so more D-Star repeaters can be shoehorned into available space.  In some geographic areas, space is not a problem but in California, Texas, and the Southeast it sure is.  Even with it’s reduced bandwidth it’s difficult to find available space.

Second, the audio quality of a D-Star radio is superior to analog. At least that’s what they say.  To my ear, it may be a lot cleaner, without white noise or other distracting  components, but the sampling rate is very low so as a result nearly everyone sounds the same.  With the volume turned down, it’s often difficult to recognize voices.  There is also a popular myth that with digital you are either “there” or “not-there”.  In reality there is a third condition referred to as being R2D2 (as in the Star-Wars robot) or as “going digital”.  When you are not being received well by the repeater, your transmission often becomes garbled and there will be words or even entire sentences that are undecipherable.  In an analog world this same condition occurs but your voice is covered by white noise.

D-Star allows simultaneous voice and data.  This is cool stuff and can be a real asset in emergency communications. On either the B-port or the C-port, you can send and receive low speed data (9600 baud) while the audio path is in use.  This requires a specific terminal program installed on an accessory computer (any laptop or desktop).  Currently, D-Chat by NJ6N is being used extensively, and a new one just out from Germany by DG1HT shows promise.
Using the A-port, high speed data (128 kb) is available and will support numerous file transport protocols.  Extensive experimentation is underway.

Tones are unnecessary, and you don’t need to know all the frequencies.  Naturally, you’ll need the frequency of the repeater you are accessing, but after that, all the frequency selection is done by the various repeaters involved in reaching your destination.  Likewise, no PL tones are required either since everything is done with data.  It is even possible to set up your radio to contact a distant station using his callsign rather than the repeater he is on.

In an earlier article on D-Star I made mention of the compatibility of D-Star and the APRS system.  Of course some sharp eyed readers caught me and wanted more information.  I was saved by technology!  It is compatible (sort of) using software interfaces.  You can see what is currently available by going to http://jfindu.net

As with any new technology, many changes are sure to occur.  Stay tuned!

Note 1: The GPS antenna is located in the microphone.  Unlike conventional GPS, the D-Star GPS won’t help you find your way around the mean streets of the East Bay, but it will report out your position and you can be tracked just like on APRS, and with the correct software interfaces even ON APRS.  If you look me up on jfindu.net, I will always be in the same place;  my IC2820H is bolted to a desk.

Note 2:  If I just key my mic, I’m not really “kerchunking” (bad form).  Every time I transmit, my callsign is part of the data header and everyone hearing my button pushing sees my callsign.  It’s not unusual for some hams to yak for extended periods without saying their callsign.  After all, everyone hearing them can also see their callsign on the screen.  Is this legal?

n6xn

About n6xn

It all started in 1968 at a small 100 Watt radio station in Napa California. Looks like I finally got my priorities straight: the career is on the back burner and the K3 is getting some air time.
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One Response to Dstar digital Radio

  1. John Wehren John Wehren says:

    Since this article was written, much has changed in the Dstar universe. For example, the article mentions that there are 166 gateways (systems) on line and 340 unique callsigns on the heard report. As I write this there are 683 gateways on line and 22,874 registered users. This article is in need of a good freshening up and I’ll do that in the near future.

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