Digital Mobile Radio is, as the name implies, digital. Originally developed in Europe, DMR is used worldwide. You have probably heard of MOTOTRBO, Motorola’s implementation of DMR. Like D-STAR, we can do stuff with DMR just not possible in the analog world.
The big difference between D-STAR and DMR are the markets they were designed for. D-STAR is from the Amateur world, and focuses on the user controlling what connections are possible over the D-STAR network. D-STAR encourages user experimentation and customization as well.
DMR is from the commercial world where the user just wants to “Push-To-Talk”. The focus is on ease of use as the radio is simply a means of communication. How and where the network connects is left to the system manager.
BrandMeister is changing DMR into a more “Amateur-Centric” mode. Much like D-STAR, the BrandMeister network lets the used decide how a repeater is connected to the network.
DMR Concepts
Just as FM and D-STAR require more than just entering a frequency, DMR has its own unique set of parameters to program. Don’t panic, they do make sense, especially if you remember DMR is designed for the commercial market, and we have adapted it for Amateur use.
To put things simply, there are several “Big Ideas” with DMR: Radio ID, Color Code, Timeslot, Talkgroup and Zones:
• Radio ID (Subscriber ID): DMR is digital, and networked, so each radio has a unique ID number to identify it on the network. In the D-STAR world this corresponds to the “MYCALL” parameter. To obtain a radio ID, go to: https/dmr-marc.net then choose Register ID.
• Color Code: This is the DMR version of PL. The Color Code for the Springhill 443.750+ DMR Repeater is CC1
• Timeslot: DMR uses magic known as “Time Division Multiple Access” (TDMA). In Simple Ham English, this means the repeater can support two simultaneous conversations by alternating between two timeslots. About 30ms is given to timeslot 1, then the transmitter flips to timeslot 2 for 30ms, then back to timeslot 1, and then to timeslot 2; you get the idea. Something like the mom who speaks to her 2 kids, allotting each of them 30ms to talk. Since you transmit on just one timeslot, your radio’s battery last longer as it is really only transmitting about half the time you have the PTT keyed. In other words, the repeater’s Time is Divided such that Multiple hams can have Access (TDMA).
• Talkgroups: DMR is designed for the commercial market where radio users typically have something in common, such as Security, Engineering, Parade Operations, etc. It isn’t very efficient to have separate repeater pairs for each group, so DMR uses “Talkgroups” to group together users who want to talk to each other. On our DMR repeaters we have several Talkgroups that allow you to talk to geographically increasing areas: local, regional, statewide, all the way up to worldwide. Talkgroups are also either “Always On” (Static for BrandMeister) or “User Activated” (Dynamic for BrandMeister). “Static” or “Always On” means just that, network traffic to this talkgroup is always on. “Dynamic” or “User Activated” talkgroups have a timer associated with them, typically 10 minutes. The practical side of this is that after 10 minutes of local inactivity on a User Activated talkgroup, it is dropped from the network connection. To start listening to a User Activated talkgroup, key up, and you probably want to talk at least once every 10 minutes as well in order to keep the network feed.
• Zones: Think of a “Zone” as a way to organize a group of channels. For most folks there are several talkgroups they wish to use, and several repeaters as well. Multiply that number of talkgroups by the number of DMR repeaters you want to use and this can make for a lot of channels. How can we keep things organized? We use Zones to give us a convenient way to organize these talkgroups. Again, remember that DMR is a commercial thing. We group our channels into Zones for ease of use. The MD380 Basic Codeplug has two Zones. SPH_RPT_DMR which contains the following channels – SPH_RPT_ID_TS2, SPH_LCL_2, LA-3122, AR-3105, LA-ARES-312222, ARWX-31051, TAC-310, Worldwide-91, North_America-93, SPH_Parrot, TN-3147, SPH_RPTPID_TS1, Scan_Only. The Direct_ANA/DMR Zone has 446.00mhz_Analog, the following DMR direct or (simplex) channels – 441.000, 443.450, 446.075, 446.500, 446.5125 and DMR-DIR-Scan. You can also add zones and set them up so they work for you.
Springhill Amateur Radio “Roll Your Own“
The following is pretty specific to the Connect Systems/MD-380 codeplugs, but the concepts are applicable to other DMR radios. Here are some of the features and items that we hope will enhance your DMR experience on the Springhill 443.750 / 448.750mhz Mototrbo Repeater. Feel free to tailor things to your own needs.
Channels
This is where all the details such as frequency, talkaround, admit criteria, color code, scan list, group list, timeslot, etc. are placed. Some of these parameters can be different if the same channel is in different zones. For example, in the “SPH_RPT_DMR” you may want to use a Group List to hear other timeslot traffic, but in your “Direct_ANA/DMR” Zone you don’t use a Group List so just that talkgroup is heard. There are lots of possibilities for customization here.
Zones
In the MD2017 and MD-380 codeplug there are two Zones one for TS1 channels called “SPH_RPT_DMR” for the Internet, and a “Direct_ANA/DMR” Zone. Each Zone has a different selection of DMR and analog channels as noted below. The idea is to show different ways a Zone can be configured, and give you some Zones to experiment with. Below is the typical channel layout for the “SPH_RPT_DMR” Zone.
• SPH_RPT_ID_TS2
• ArkLaTex – 31229
• AR (Arkansas) – 3105
• LA (Louisiana) -3122
• LA_ARES-312222
• ARWX – 31051
• North America _ 93
• World – 91
• TAC 310
• TN-3147
• SPH_RPT_ID_TS1
• Parrot
• Scan Only
Talkgroup DescriptionsTalkgroups are also either “Static” (“Always On”) or “Dynamic (“User Activated”, which is “PTT” for us Old Skool DMR Guys). “Static” means just that, network traffic to this talkgroup is always on. Dynamic talkgroups have a timer associated with them, typically 10 minutes. The practical side of this is that after 10 minutes of local inactivity on a dynamic talkgroup, it is dropped from the network connection. To start listening to a dynamic talkgroup, just key up.
• SPH_RPT_ID_TS2: This is the talkgroup for the local repeater. Traffic here is not sent over the network; it is just heard locally.
• ArkLaTex: We hope in the future Repeater Operators will link other DMR repeaters to this talkgroup, that will eventually be in the ArkLaTex Area. Good place for a QSO with other ArkLaTex people. This talkgroup is a Static (or Always On) Talkgroup on TS1
• AR-3105: This talkgroup is on Arkansas State Wide talkgroup..
• LA-3122: This Dynamic (or User Activated) talkgroup is on the Louisiana Statewide Talkgroup.
• LA_ARES-312222: This Dynamic (or User Activated) talkgroup is on the Louisiana Statewide Amateur Radio Emergency Services Talkgroup.
• ARWX-31051: This Dynamic (or User Activated) talkgroup is on the Arkansas Statewide Amateur Radio Emergency Services Talkgroup.
• North America: Links BrandMeister DMR repeaters in North America.
• Worldwide: Links BrandMeister DMR repeaters across the world.
• USA/3100 Brandmeister North America Talkgroup (TG 3100; old “Nationwide”)
• TAC 310: Dynamic TG connection between DCI TAC 310 and BrandMeister. Also available: TAC 311, TAC 312
Digital Contacts
This is the most dynamic part of the codeplug as here you find the radio ID aliases (Private Calls) and talkgroup numbers (Group Calls). As more folks get involved in DMR, more contacts are added to the list. You can add contacts too, not only new radio IDs, but also new talkgroups. So if one of your DMR repeaters starts carrying a new talkgroup, you can add that in here. The “Contact Name” is what appears on the screen, “Call Type” is “Private” for a radio ID and “Group” for a talkgroup, with “Call ID” being either the radio ID or talkgroup number.
Digital RX Group Call and Group List
These two work together to let you listen to more than one talkgroup at a time; here is how it works. Each channel can have a Group List. This Group List references a Digital RX Group Call which contains Group Calls from the Digital Contacts list. The Digital RX Group Call gives us a way to monitor more than one talkgroup when you are on a channel. The practical result is similar to scanning the talkgroups listed in the Group List.
Text Messaging
These are the “Quick Text” messages you find under the “Messages” icon. They are for text you send frequently, such as “Please meet me on Local”. You can also enter messages from the keypad as detailed below.
To Send A Text…
• Right arrow key to the envelope icon. The screen will show “Messages”.
• Press “O” (O is your “enter” key).
• Arrow right to “Write”. “Quick Text”, “Sent Items” and “Drafts” are your other right arrow choices.
• “O” for enter.
• To enter your text, select letters using the keypad, i.e repeatedly pressing the “2” key will cycle through a,b,c,2. The # is space, * is clear, and hold down 0 to shift case
• When you are done, press “O”…
• …at the “Send” prompt, press “O” again.
• Left arrow for “Manual Dial”…
• Press “O”.
• Enter the radio number you wish to send the message to. Hint: All LA radios start with 3122, all AR radios start with 3105, so you probably just need to remember the last 3 digits.
• Press “O” to send.
• Await a reply 🙂
You can also re-send a message from “Sent Items”, send a message from “Drafts”, in addition to the “Quick Text” messages.
Practical DMR: Scanning all traffic on a repeater
Custom Scan Lists
• “SPH_RPT_DMR”: Scans the LA-3122, AR-3105, ArkLaTex-31229, SPH_RPT_ID_TS2, TAC-310 on the Springhill DMR repeater.
• “Direct-Scan”: Scans 446.000mhz Analog and all DMR Simplex Frequencies for
activity
• Other Scan channels will be setup as needed or requested.