Diving into D-STAR – 1

By Toshen, KEØFHS – last updated Dec 2017
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D-STAR logo
The D-STAR logo is a
registered trademark of Icom

Why bother?

When I first dove into D-STAR, I knew nearly nothing about digital voice and quickly found myself drowning in a big bowl of bewilderingly murky information soup. SOS!

So if it's that bewildering, why even bother?

I'll jump a bit ahead here and share one tidbit: at one point early in my exploration of D-STAR, I linked to a reflector and heard a guy in San Diego, California chatting with a chap in Yorkshire, England. That was the moment I became hooked!

Just think of it: worldwide communication with a Technician class license, a bit of effort and learning, and some fairly simple equipment.

Of course, the real goal isn't to just listen but to actually chat with people. This is the story of how I got there.

Today's amateur radio experimenter is as likely to use a keyboard as a soldering iron for experiments, and as a digital enthusiast, I can only cheer and encourage you to get involved and have some fun.

– Don Rotolo, N21RZ, Vocoding: Creating Digital Voice, CQ Amateur Radio

Don't feel like reading a long article? Jump to: tl;dr? Quick version!

1) What is digital voice?

The simple answer is that digital voice (DV) uses digital rather than analog audio. But what does that really mean? For me, it was all quite murky when I first started looking into it, and it took me quite a bit of exploring and head scratching to begin figuring it out.

This section provides an introduction to the basics of digital voice and hotspots, including links to some helpful websites, articles, and other content, in case you want to dive in more deeply. You also can find all the links together on the Notes page at the end of this article: Links to resources I've found helpful.

1a) Alphabet soup

As I began flailing around in the digital voice murkiness, one of the first things I figured out is that it's actually a bit like a big bowl of alphabet soup … it's absolutely crazy how many acronyms are floating around!

Bowl of alphabet soup with digital voice acronyms floating in it
Alphabetsoupese by Toshen, KE0FHS
Derived from an original photo
by Leo Reynolds. Some rights reserved.

Even worse, sometimes the acronyms are spelled out differently, for example, D-STAR vs DStar, or DVMEGA vs DV MEGA vs Dv-Mega, which makes searching for information more challenging. In this article, I try to consistently use the official or standard version of acronyms, except when I quote others.

Other times, it isn't easy to determine what an acronym actually stands for, for example, in relation to digital voice I've seen DCS defined as Digital Call Server, Digital Communication Systems, and Digital Call Service, and I'm still unsure which is correct. (Perhaps it stands for Darn Confusing Stuff? ! )

Since there's no avoiding this craziness, you just have to accept it as part of the price of admission. And don't worry, by the end of this article, you'll be speaking "Alphabetsoupese" as fluently as is possible!

1b) Multiple systems

The next thing I understood is that D-STAR is just one of several competing digital voice systems being developed, though it's the first.

The logos of D-STAR, DMR, System Fusion, and FreeDV

The Japan Amateur Radio League began development work on the Digital Smart Technologies for Amateur Radio (D-STAR) standard in the late 1990s and published it in 2001. It was developed specifically for amateur radio use, and started to gain traction in the U.S. around 2006.

The D-STAR standard has been adopted primarily by two first-tier amateur radio equipment makers, first by Icom, the D-STAR trailblazer, and more recently by Kenwood. By now, it's being used by tens of thousands of amateur radio enthusiasts worldwide.

It's also a mostly open standard (except for the vocoder I discuss in the following "Alphabetsoupese - example 1" note), so it's being used for lots of experimentation, which means there's a bunch of interesting homebrew and small manufacturer hardware and software available.

Among the other digital voice systems being developed are DMR (Motorola, Hytera, Tytera, Connect Systems, and others), and System Fusion (Yaesu).

There's also a totally open system in development, a combination of FreeDV software and an open source speech codec (vocoder), Codec 2. There's a version of FreeDV available for HF, but it hasn't yet come to the VHF and UHF frequencies (as of Nov 2017).

1c) Transceivers, repeaters, and reflectors (oh my)

Just as you can use analog transceivers in FM mode, you can use digital voice-capable transceivers in DV mode to talk directly from radio to radio simplex¹ or via a repeater (as long as it's a digital voice repeater).

Diagram of DV HTs connecting via simplex and via a DV repeater
[1] The U.S. DV simplex frequencies are 145.670 (2 M) and 446.225 (70 cm)

It gets even more interesting when digital voice repeaters are bridged together, enabling groups of two or more people, even far flung, to participate in something that is like a conference call.

Diagram of DV HTs connecting via DV repeaters to a reflector

In the D-STAR world, this technology is called "Reflectors" (transmissions are reflected to all repeaters linked to the reflector), while DMR calls it "Talkgroups" and System Fusion calls it "Rooms."

Linking to reflectors to participate in a call or net is a big part of what playing around in the worldwide D-STAR playground is all about.

Here, too, there are multiple systems being developed and used simultaneously. Within just the D-STAR world, there are four main types:

  1. REF – The DPLUS reflector system, a closed proprietary system developed by Robin Cutshaw, AA4RC, is the first generation of D-STAR reflectors and still much in use, especially in English-speaking countries. An example is REF001 in London, referred to as D-STAR's "Mega Reflector." REF directory.
  2. XRF – The Dextra X-Reflector system, originally created by Scott Lawson, KI4KLF, is the second generation of D-STAR reflectors and is open source. An example is XRF720, which links several Colorado statewide D-STAR repeaters. XRF directory.
  3. DCS – The Digital Call Server reflector system, developed by Torsten Schultze, DG1HT, is an even newer system that is being used worldwide. An example is U.S. Reflector DCS006. DCS directory.
  4. XLX – The XLX reflector system, being developed by Jean-Luc Boevange, LX3JL, and Luc Engelmann, LX1IQ, is the newest system, which they describe as "the first and only multiprotocol Reflector system until now and supports all standard D-STAR protocols like DCS, Dextra and DPlus fully transparent." XLX directory.

To learn more, read Reflections on Reflectors: A basic tutorial on DSTAR reflectors, 2016, by Bob Scott, W6KD.

Same difference

While there are some differences between D-STAR, System Fusion, and DMR, the three systems share many similarities. Given their shared similarities, perhaps the most surprising thing is that they don't talk to each other. They are like three side-by-side playgrounds, all with similar swing sets, slides, sandboxes, and climbers, but with arbitrary fences separating them.

If you want to learn more about the comparisons of the digital voice systems, here's some good information:

For an update about progress being made breaking down the fences between the digital playgrounds, see: 4d) Constellations: a big leap for digital voice.

1d) Personal access points (hotspots)

This is where it gets really exciting and fun, at least for me. One more piece of the puzzle is figuring out how to get onto the digital system when you're not within radio range of a digital voice repeater.

Fortunately, there are innovative hams creating hotspots and software that enable a ham with internet connectivity to link directly to reflectors or DV repeaters, bypassing the need to transmit from the radio to a DV repeater first. Basically, these devices act as your own personal digital voice repeater and gateway.

Diagram of DV HTs connecting via personal access points to a reflector and a DV repeater

There's another nice aspect of the hotspots: since you link directly to a reflector via a hotspot, you don't tie up a DV repeater the way you do if you use your radio to send a command to the repeater to link it via its gateway to a reflector for your personal call on that reflector. This may make a hotspot interesting even for someone who lives within range of a DV repeater.

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