As a newly minted ham, the term Digital Radio is one of areas that is going to cause you some confusion. Lets try and clear this up straight away.
The following however is not meant to be a definitive guide on Digital Data and Voice Modes. Even as I re-read it now, I can see many more modes missing, but the purpose of this guide is provide that base concept, so you can research yourself with some direction and understanding of what you are reading.
DMR / D-STAR / SYSTEM FUSION (YSF/C4FM) are all examples of Digital Voice where the speech is encoded before transmitting it, and decoding it on the other end. One very important thing to remember is that this is encoding, not encryption (encryption is not permitted under our Regulations). And the best way to define Encryption is that Encryption needs a “non-public” defined key to encrypt or decrypt.
Encoding and Decoding is done with publicly available algorithms for the sole purpose of “digitising your voice for transmission”.
Just before we finish this very brief explanation on Digital Voice, we need to make it clear that D-STAR is able to perform both Voice and Data communication, although the voice is the primary use of D-Star.
Generally, these digital voice modes are primarily found on products produced for the UHF/VHF bands, however D-Star and to a lesser degree C4FM may be also be found on HF (10m band)
FT8 / FT4 / JT65 / PSK31 / AX25 / RTTY / SSTV / APRS (amongst many others) are examples of Digital Data modes. One of the most important things to note is that they generally rely on the digital processing of computers or hardware.
As the above are are digital signals, they are able to transmit and receive information with less interference from the normal sources that affects voice. In fact, FT8 transmissions appear to be able to be received even with high noise floor levels, in most cases inaudible to the human hearing.
Unlike Digital Voice, Digital Data Modes will utilise existing radio design and normally the radios will include a sound card built in to their product or you can install an external sound card / audio interface. So typically, you will find HF bands being the most popular for the digital modes (at least for long distance), but definitely these modes will work on VHF/UHF systems as well.
This article mainly covers Digital Voice, which is what we will progress into now, but have a look around, you will see that we discuss the Digital Data modes in more detail in another article on this website
Digital Voice in more detail
I suspect that you already have a Analog FM radio of some description, as it is usually one of the first purchases that many new hams make due to the lower entry costs. Quite often the next purchase is a radio capable of Digital Voice, but which one do you go for?
Before you make that commitment, you really need to do your research, and really understand what you are reading. Some of the commentary you will read from Websites, Blogs, forums with be from all different parts of the country, different parts of the world, and they will all have their own agendas. Just to show you some figures (extracted 2022) of repeaters that will support the digital voice modes per country are
- 2159 YSF
- 2077 DMR
- 1188 Dstar
- 82 DMR
- 52 Dstar
- 39 YSF
So if you are on a blog or website or forum, you need to work out where the author lives, or find local forums. As you can see, in the U.S. there is going to be a massive bias to the YSF mode and to a similar degree the DMR mode. In Australia, DMR has come out on top, but D-Star is not that far behind. But you need find out what is best for you. Use the Repeater Maps and look at whether you have a repeater close by and what it supports. Also take into consideration (particularly in Australia) how sparse some of the Repeater locations are (that support your Voice mode), which is important if you want to use the repeaters, but for all modes, if you decide to run a hotspot (and you have a good Internet link) then you can use any of the Digital Voice modes and buy the radio based on price / functionality that suits you.
Also take into consideration that many of the manufacturers (at least at the production level) have aligned themselves to a particular mode
- C4FM – Yaesu
- D-Star – Icom
- DMR – Hytera/Kydera/Anytone/TYT/almost everyone else including Chinese Manufacturers
Note : DMR was a commercial standard, so companies like Kenwood manufacture DMR radios and repeaters for the commercial market that are not for the Ham Radio Market.
So, this should be taken into consideration as well, as an amateur may have decided to go with C4FM as he has a stable of Yaesu radios, and wants to remain with the brand, so his bias might be with a manufacturer and not necessarily the Digital Voice mode.
And also remember, Yaesu and Icoms are a lot lower cost in the U.S, as Australia’s Exchange rate and freight costs drive the prices much higher, so some of the decisions on radios and modes may very well come down to radio unit costs, with Chinese manufacturers looking a lot more attractive.
One more thing, as a new foundation licence holder, you may not yet have an Analog VHF/UHF radio. Almost all the DMR/D-STAR/C4FM radios are also analog radios as well. So if you want to avoid purchasing a Digital Voice radio and a separate Analog radio, this might be the way to go. The one caveat, is that many of the Analog radios use a common application to program the radio called CHIRP, which is easy to understand and you could have your radio up and running in literally an hour with repeaters programmed. Digital Voice Radios, as analog is not their primary mode, can be hard to program, and the concepts of what you are entering can take weeks to understand (almost a 10x learning curve over analog)
DMR originally started off as a Commercial system that was adopted for Ham use. This is one of the more popular ones in Australia. The main thing to remember is that your equipment that you purchase must be Tier 2 compatible.
With DMR you will learn about Talk Group Networks which are namely DMR MARC (VK-DMR) and Brandmeister. There are others, but these are the main ones supported by repeaters, and you should also check that your local repeaters are connected to the talk group network you want.
You will learn about Talk Groups (TG’s), common ones are TG1 (worldwide), TG505 (Australia Wide), TG3803 (VIC wide), TG3804 (QLD Wide). So as a very quick example, we wanted to put a call out to all Queensland Hams, we would select 3804 Talk Group on my radio and place a call. This will key up the talk group across all DMR repeaters that are part of the 3804 Talk Group. Likewise if I want to reach anyone in Australia, we would use the TG505. This means that this would broadcast across all repeaters in Australia.
One of the main things you will learn is about the repeaters and whether the groups are full time (static) or part time (Dynamic). A full time group on a repeater, does not need any intervention to monitor it, you dial the TG on the radio and you will hear the conversation. A part time group, you will need to learn what a “Kerchunk” is, and basically its pressing the PTT key in…..now this goes completely against the grain of what we are taught is good etiquette, but it’s what you do. This will open up a TG on the repeater. So after you “kerchunk”, the TG will stay open for a prescribed period. If you commence talking, you don’t need to “kerchunk” again unless you do not talk for a long period. Generally, you will find that your local repeater will have a few static TG’s, normally one for the area that it is in, another for the few areas next to it, usually one for the country, and one for the NET’s TG.
DMR also supports private operator to operator calls via simplex, repeater and hotspot networks.
Finally one more thing, if you don’t have a DMR repeater that you can reach, or your repeater doesn’t connect to your Talk Group Network that you want, you have the option of using a Hotspot, which is in effect is a “personal repeater” (about $AU100 worth of hardware) which you connects to the Internet (and therefore the talk group networks), and your radio can connect to this. Read about hotspots at the bottom of this article.
Ok I lied, one more thing on DMR, you are going to come across this wretched word called “Codeplug”. Pure and simple, it has nothing to do with code, nor is it a program. It is very purely a configuration file with a large number of settings. Your DMR radio can be made to use just your local repeaters, or you can set it with every repeater in Australia, so you can use DMR anywhere there is a DMR Repeater. You can program all the Analog repeaters and it will use those for analog.
- What is DMR – A good Australian site that goes into detail about DMR
- DMR In Australia – Another good site to read
- Australian DMR Repeaters – A current map of Australian DMR Repeaters
D-Star is actually one of the oldest Digital Modes developed purely for Ham radio from by the Japanese Amateur Radio League.
One of the advantages of D-Star, is that your use of the radio, repeaters and reflectors is all dynamic. Now what I mean by this is that with DMR, if you have not put the talk groups you need, the repeaters for the area that you are going into, it is not the sort of thing you want to do on the road, or even in a motel room. DMR codeplugs are meant to have all the repeaters, all the talk groups setup that you will need. If you find that there is a new Repeater or a repeater that needs to be changed at your location, it becomes onerous.
D-Star is different in that your radio allows you to enter the “routing” dynamically on the radio, both the routing via the repeater, routing via the Gateway, and routing via the reflector. So if get an email from a fellow ham asking to meet on a particular reflector, and you are out of town, you can complete the connection in a few minutes. What may not be clear here is that your radio (at least the Icom 705 – but maybe others can do it) may even be able to via your Wireless Access Point to the Internet and then route via a gateway (in effect what DMR users do, except that DMR users need the additional hot spot)
D-Star in operation – An older U.S. Video, but worth watching the basic operation of D-Star Radio routing
Australian D-Star Information – Australian site to start with on D-Star (watch the link above first)
D-Star for dummies – PDF Download – A great read and well put together on D-Star
List of Reflectors World Wide – shows the Australian Reflectors as well
Now right from the start, I will state that my knowledge of the C4FM mode is very limited. Other than a few demonstrations and discussions with C4FM users, that is the limit.
One of the first things you will notice is that the units are generally more expensive, and particularly in Australia, whilst it is not the only thing that impacts C4FM popularity, it does matter, particularly with Exchange Rates just pushing the prices over the “value” mark, particularly for Ham Radio newcomers.
One of its advantages however is that it has an automatic backwards compatibility with Analog FM and the repeaters do the same.
Like D-Star, connecting to repeaters not necessarily pre-configured is not an issue as you can do it dynamically on the Radio. The one thing that you will become aware of is that your radio will need to connect to a Wires-X capable repeater or Gateway (a Gateway is a ham operator who has a node connected to the Wires-X Network – only particular models will work as a Node). Again you access rooms very similar to the other digital modes, and the strength of the network is due to the interconnectivity of Repeaters and Gateways over the Internet, providing almost world-wide coverage.
Again like D-Star, the C4FM radios menus are updated real-time, making it easier to perform dynamic configuration.
Australian C4FM Repeaters – list of C4FM repeaters in Australia
Now, if your passion is in a certain area, you could probably pull the above apart into a million pieces. That’s why it’s hard to write an article as there are so many twists and turns, which can depend on the persons ability, budget, nomenclature used and if you tried to cater for everyone, any article can become an unreadable mess.
So even as a newcomer, whilst the information and the concepts are generally correct, you need to look at a particular aspect for yourself (e.g. take DMR and perform your own research). For instance, you need to look at APRS and whether your radio will do it, or does it just have a GPS (which is not necessarily APRS). Is APRS supported on your Repeaters – might be on Analog, but not DMR, and these limitations might be just in your country alone.
Then we have the subject of Hotspots which can have its own article as it is a very extensive subject, and these hotspots (which as mentioned can be looked at as personal repeaters) which support D-STAR / DMR / FUSION. These Hotspots can also be used to talk between Fusion (C4FM) and DMR and other modes, however again this is a subject that does outside the scope of this document as there are ifs & buts that need to be considered.
So as a final wrap up, these systems all work well. you will see some documents mention one is better than the other in voice quality, another is better than the other in range, another is more superior in design, but when it comes down to it, they are all quite good, so it’s really going to come down to budget, what repeaters you have close to you, how much time you have, and what your fellow hams have already.