The DM-1701 is an inexpensive dual-band VHF-UHF DMR/Analog radio. It includes some features that are not legal on the amateur bands such as two different modes of encryption, but overall, it is a nice radio that’s rugged enough for commercial use. If you’ve attended NC Scout’s RTO course recently, you know that he’s picked up several of these radios for student use. This article is going to give you some ideas for setting them up for your own team.
Before we get into setting up the radio, let’s talk a little bit about Digital Mobile Radio (DMR) and what that standard brings to the table. First and foremost, is digital audio. Like digital television, signal quality is excellent right up to the point where the radio can’t decode it anymore, where it fails quickly. Analog radio, on the other hand degrades steadily as the distance between stations increases. In practice this means that you will get better audio longer with DMR, but you’ll be able to understand the analog signal over a greater distance. In addition to better signal quality over most of its range, digital audio has the advantage that it’s not decodable by an analog only receiver, lending some obscurity to the message being transmitted. The next feature that is particularly useful for us is SMS messaging. The DM-1701, according to the manual, lets us create messages of up to 144 characters total over a maximum of 50 lines. In addition, you can create and store messages to use a template, greatly simplifying creation of formatted reports. Finally, because DMR divides each frequency into two time slots in a narrow bandwidth, it also uses your battery more efficiently. (As an aside, DMR signals have a very distinctive sound because of the time slots, unlike D-STAR and C4FM, which sound more like white noise.)
DMR is designed around the concept of contacts, channels, and zones. Broadly speaking you can think of contacts as who you want to talk to, channels as how you want to talk to them, and zones as where you want to talk to them. When you combine contacts, channels, and zones into a program for a specific radio, you have created what is known in DMRspeak as a codeplug. Many, many videos are available on YouTube to guide you through the process of creating a codeplug. Thankfully, most of that information isn’t needed for our purposes and we can simplify things considerably.
Normally, each DMR radio is given a unique Radio ID. For amateur use, this is an ID associated with your callsign. That’s NOT what we want for our team radios. The default ID used by the Customer Programming Software (CPS) that comes with the radio is 1234, and that will work for our purposes. The ID is set in the General Setting window. You can see what that looks like on my radio at right.
You’ll also need to pay attention to the Freq/Channel Mode. A or B must be set to Freq to access the VFOs. I have my radio set to start up with band A in VFO mode, and band B in Memory Recall. You can change that on the fly by using the up or down arrows to select the band, and holding down the red back button until the mode changes.
We’re going to concentrate on using the two VFOs available in the DM-1701, with VFO A in the digital mode, and VFO B in analog. With a few exceptions, we’ll be staying away from memory channels. This limits the amount of information stored in the radio to be exploited if the radio is compromised. We’re also not going to program any repeaters and Internet-connected talk-groups.
Contacts in DMR can be group calls, private calls, or all calls. We only need to concern ourselves with group calls. You can think of a group call as like an analog repeater. Everyone tuned in to it can hear the traffic being passed. Most DMR repeaters have multiple talk-groups available and each of these would become a group call contact in a normal radio’s codeplug. By limiting ourselves to simplex operations, we’ll only be creating two contacts as shown below.
Contact One will be our principle call group for intra-team communications. You can give it whatever Call ID you’d like, but be forewarned, if you try to make your team radio do double-duty as a conventional DMR HT, you can easily get yourself into trouble. For example, Call ID 1 is, in some systems, a world-wide talk-group. Far better to have one codeplug for use as a team radio, and to create another for use as a normal DMR HT.
Contact Two, should stay with Call ID 99. This is the nationwide convention for DMR simplex, and we are going to program those channels. To my mind there are a couple of advantages to doing so: first, they help us stay legal as hams when we’re practicing; and, second, it makes operation with other folks using DMR a little easier because they’ll likely to be using the same convention and band-plan.
With creating the contacts out of the way, we’ll set up the VFOs next. This may be a bit hard to see, but the window shows VFO A in digital mode with a bandwidth of 12.5 kHz. Set your time out timer (TOT) to whatever suits you. Choose a frequency to be the default for that VFO. You’ll see later that I’ve chosen one of the standard DMR simplex channels. The Admit Criteria sets what has to happen before the radio will let you transmit. In my case, Channel Free, keeps me from doubling with my any of my team. On the Digital Data side of the window, we have TEAM COMMS (Contact One) selected as the Contact Name. We’ll use GroupList1 to ensure that we receive voice and texts from our contacts. This group list contains both contacts. If you’re on a frequency in use by someone using the 99 call ID, you will hear their unencrypted traffic. The color code is the DMR equivalent of a CTCSS tone. All of your team must have the same color code selected and by convention for simplex, that’s CC 1. You should also all have the same time slot selected, even though it doesn’t make a difference in simplex operation unless the DCDM (Dual Capacity Direct Mode) Switch box is checked. Setting the In Call Criteria to Follow Admit Criteria keeps things simple. VFO B will be similar, but in Analog mode with a 25 kHz bandwidth. In my case I’ve selected the UHF calling frequency of 446.000 MHz.
We could be finished here if we wanted to be, but I think there are advantages to creating channels for the GMRS/FRS, MURS, and Weather frequencies, and I’ve done that. The GMRS/FRS and MURS frequencies have all been assigned to their own zone to simplify using them as a bubba detector. I’ve also created a Scan List containing those channels. Similarly, the Weather channels have their own zone and scan list. The weather channels are all receive only. Since it is illegal to transmit on GMRS, FRS, and MURS with radios not certified for those services, those channels should also be receive only.
I’ve also created a separate zone for the conventional DMR Simplex channels and the DMR SIMPLEX contact. Again, I did this for interoperability and to help keep me legal. The national digital simplex frequencies are: UHF: 1) 441.0000 2) 446.5000 3) 446.0750 4) US & Europe 433.450 and VHF: 1) 145.7900 2) 145.5100 with U3 and V2 the most used. All those channels are color code 1 and time slot 1. I have the admit criteria as Channel Free, although you’ll often see recommendations to make it Always.
You can set up the programmable buttons to suit your own operations, but I would strongly recommend that they be the same across all the radios and codeplugs used by your team. Since there aren’t any lables on them, you need to develop some muscle memory as to what they each do.
There are some things with these radios that don’t work the way I would have expected, and may also be common to DMR radios. Since this is my first dive into the DMR pool, I don’t have enough experience yet to know. First, while scanning through the VFO, you’ll see the frequency display stepping through the band. That’s what I expected. In memory mode, however; you won’t see the display changing, other than displaying a scanning icon, until a signal is received. At that point, the display will change. On an analog channel, you’ll see the frequency displayed, and on a digital channel, you’ll see the Radio ID of the transmitter.
That’s about it for our team radio. You won’t need to install the entire DMR Radio ID database, and you won’t be setting up any local repeaters. I would encourage you to create a separate codeplug for use on your local repeaters or a digital hotspot that you can use as a walking around radio. That’ll let you get more comfortable with the radio, and particularly if you program the codeplug yourself, will give you a much better understanding of how the DMR world is organized.