Beginners Guide To D-STAR
Above: Icom ID-51E Plus set to work through a D-STAR ‘DV Mega” UHF hotspot
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 frequency-division multiple access and minimum-shift keying in its packet-based standard.
There are advantages to using digital voice modes are that it uses less bandwidth than analog voice modes such as amplitude modulation, frequency modulation, and single sideband. 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 there is no multipath propagation.
D-STAR compatible radios are available for 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.
D-Star Components of the D-STAR Network
D-STAR Repeater System
A D-STAR repeater system is typically composed of a repeater controller, 1.2GHz, 70cm or 2mtr digital voice repeater, digital data repeater and the Internet gateway PC.
The D-STAR repeater operates similar to an existing analogue repeater. That is a simple relay of transmit and receive communication within or across the 2m, 70cm or 23cm bands.
When D-STAR repeaters are connected with the Internet gateway, the D-STAR system relays the received data over the Internet. Your message will get through virtually to anywhere in the D-STAR system.
As authorised users make their initial transmission to a D-STAR system, the call sign information attached to the digitised voice packets is recorded by the repeater controller. The controller then shares the information with other D-STAR systems through the D-STAR gateway registry. The registry is maintained on gateway servers located around the world. When an authorised D-STAR user makes a call to a call sign not currently registered on that repeater system, the registry allows the repeater controller to route the call to the repeater on which the targeted user was last registered.
A reflector can be considered to be similar to a repeater, but with no RF capabilities. Reflectors are Internet connected servers, generally in data-centres, which receive a transmission from a connected gateway (via the Internet) and send it out to all other connected gateways for retransmission, via RF in the case of a repeater.
Reflectors are basically a conference bridge for D-STAR. They allow multiple D-STAR repeaters and Dongle users, from around the world, to be joined together and whatever information is transmitted across one of the repeaters is repeated across all of the connected repeaters.
So, what does all this mean to me?
So much for the definitions, but what can we do with DSTAR and why would you want to use it?
- Icom are the only company who produce and sell DSTAR radios and as there is no competition, they set their price and we have no choice but to pay their price if we want to use their radios. Icom DSTAR radios are more expensive than the equivalent analog FM mobile/handheld. However, the DSTAR protocol is ‘open’ so anybody can produce a DSTAR ‘device’ - more of this below.
- An Icom DSTAR radio can be used as a standard FM radio as well as being used for DSTAR communications.
- An essential part of the DSTAR system is the Internet connection. To take full advantage of DSTAR, your transmissions have to be able to get to the Internet by some means.
- If you are within range of a DSTAR repeater, then this will be your route into the Internet (providing the repeater is connected to the Internet as most of them are).
- If you are NOT in range of a DSTAR repeater, there are alternative ways of accessing the Internet such as a local ‘hotspot’ at your QTH. A hotspot is essentially a low powered repeater connected to your home Internet. An example of a DSTAR hotspot is the DVAP or DV Mega.
What can I actually do with DSTAR?
What can you do with DSTAR that you can’t do with standard analog radio and repeaters? Well, take a look at some of the examples below in the ‘Is it Radio?’ section. One of the most obvious factors is that you can use the DSTAR system WITHOUT a DSTAR radio (and certainly at a lower cost that purchasing a radio). The minimum requirement for getting on DSTAR is a fairly basic computer with a spare USB port, a DV Dongle and a cheap computer headset. So, if you are unable to erect that antenna for 160/80/40m etc, but you still want to get on the air and work further than line-of-sight, then DSTAR might be for you.
But is it Radio?
Ah, the age old question - and one that some amateurs will use to completely dismiss any mode of communication that doesn’t use RF alone.
This is something that you will have to consider and to make your own decision. Does DSTAR ‘work’ without a repeater or reflector and the Internet. The short answer is ‘No’ although you could still make simplex contacts, but you could do that with a conventional analog radio at a fraction of the price.
How is using DSTAR any different to other Internet modes of communication such as Skype or Echolink (or even a mobile phone?) Depending on what equipment you are using, it may be no different at all, but that’s missing the point really. Lets take a look at a few examples.
- I’m sitting at home and I’ve got my DV Dongle plugged into the computer. I’m connected to REF001C and I respond to a CQ call. The station tells me that he’s in a small apartment in New York and because he can’t erect and aerials, he’s also using a DV dongle. So, no RF, 100% Internet and very much like Skype - although I chose the reflector and therefore the ‘flavour’ on the QSO.
- I’m at home but I’m round and about the house and garden. I’ve got the DV Mega and Raspberry Pi hotspot running and it’s connected to the Internet using my home WiFi. I’ve got the DSTAR handheld clipped to my belt and it’s tuned to the DV Mega ‘simplex’ frequency. From the bottom of the garden, I send a command from the handheld to to the DV Mega to connect to reflector DCS005B and the DV Mega transmits back to me “Linked to DCS005B.” I set the handheld to ‘Use Reflector’ and I can chat to my hearts content - to a maximum distance of about 100m from the DV Mega hotspot. So RF from the handheld to the hotspot, RF from the hotspot to the internet via WiFi and then into the Internet network. What happens at the other end is entirely dependant on how the other station is operating.
- I’m out for a walk and fortunately I’m in range of my local DSTAR repeater. If I want a ‘local’ QSO, I’ll use the repeater just like a conventional analog repeater. However, if I want to reach out further, I’ll use the radio to send commands to the repeater to connect to another repeater or reflector of my choice via the Internet ‘gateway.’
- I’m doing some voluntary work driving a small mini-bus on a private estate carrying visitors up to the castle. I’m out of range of a DSTAR repeater and the castle doesn’t have WiFi and even if it did, it wouldn’t cover the 1.5 mile circuit of my route. Fortunately, I do have a mobile phone signal and access to ‘3G’ Internet data. I take my DV Mega with me and power it from a small ‘power pack’ battery. I either use the WiFi from the mobile phone (tether) or a small ‘MiFi’ portable 3G unit and I’m good to go. The handheld ‘speaks’ to the DV Mega and the DV Mega connects to the Internet via the phone/MiFi WiFi connection. Between passenger runs I have a number of QSO’s with stations all over the world.
So, there are a few examples of how you can use DSTAR when at home or out and about. It’s a very flexible system and it’s very enjoyable to experiment with the mode.
Above: A ‘DV Mega’ D-STAR Hotspot. The DV Mega board is mounted on a Raspberry Pi single board computer. This example uses a USB WiFi adaptor and therefore only needs a 5v power connection to be connected to be up and running
There are many DSTAR resources available on the Internet. Here are a few to get you started: