Ham Radio DMR 101

Assumption: You are a licensed amateur radio operator with some experience operating on 2 meter and 440 band FM repeaters and have a sense of their abilities and limitations.

What you need to know before you start reading: DMR is a commercial radio technology invented to give FCC Part 90 spectrum users a choice when they had to make a decision regarding narrow banding their wideband FM radio systems. You won’t find things like VFO mode on a DMR radio where the radio operator can change frequencies on the fly. The unique identifier for your DMR radio consists of several digits, not a call sign like you will find in a Fusion or a D-Star radio. All of the information in your DMR radio you put there using programming software and a programming cable. This means that when you travel, you need to plan ahead of time and program your radio before leaving home. You can’t add frequencies, color codes, and talk groups while you are driving down the road. We think that talk-group-based communications brings to ham radio advantages that negates the disadvantages of using commercial radio equipment. Additionally, DMR portable and mobile radios are available at affordable prices, unlike radios for some other commercial/government-oriented digital radio schemes.

Before you buy a radio: Before you purchase your first DMR radio, verify that there is an open DMR repeater in your area and that you have the specific information needed to configure your new radio for operation on that repeater. Some new DMR repeaters are home repeaters which means one in your city might not provide coverage to your neighborhood. When shopping for a radio, know that some DMR radios are dual-mode capable and some are DMR-only. If you decide that dual-mode DMR/FM is what you want, verify that the radio of your choice can operate wideband FM (25 KHz channels verses narrowband 12.5 KHz channels). Radios marketed to Part 90 users have no need for wideband FM after 1/1/13 but us hams still need wideband capability. So far, there is no such thing as a dual-band DMR radio so you need to find out if a 2 meter or 440 band radio makes sense for your area. Ham radio DMR is DMR Tier II. This is conventional digital repeater operation. DMR Tier III is trunked digital, which is popular with Part 90 entities that need higher channel capacity than can be provided by one repeater.

As you begin your DMR education, it may help to look at multiple sources of information.
First, take a look at DMR-MARC’s Guide to DMR: http://www.dmr-marc.net/media/Amateur_Radio_Guide_to_DMR_Rev_I_20150510.pdf
Then, check out the BrandMeister USA guide: https://brandmeister.us/files/US_BM_User_Guide.pdf


Academics


We are about to throw a lot of new terminology at you. The last section of this page is the Terminology section. Scroll down there when you hit a term that is new to see an explanation.

Talk Group - If you are like most hams, this is a completely new concept. Hang in there, you need to know this for DMR to make sense. A talk group is a logical grouping to enable communications among the radios of a specific group of radio system users. Or, you could look at it as a way of ensuring that you hear and participate in the communications only among your group, filtering out the traffic of all the other users on a given repeater. In your radio, you have programmed in each channel, the frequencies and color code for the repeater you intend to communicate through. In addition to those two parameters, you need to configure the talk group number and time slot number. When all of those parameters are valid, then you can monitor and transmit through a given repeater to a specific group. The participants in this group could be local to your repeater or they could be on the other side of the planet. Or, you could have multiple participants local to you AND multiple participants on multiple repeaters that are located in other states and countries. There is a numbering plan that we participate in as a BrandMeister networked repeater owner and maybe some examples will help clear this up.

USA wide 3100 - If you want to work random hams that are located throughout the US, this is the talk group to have in your radio. It is frequently active and you always get a response to a general call.
Callsign Region 7 31097 - Established for communications within the 7 call region including Washington, Oregon, Montana, Utah, Idaho, Wyoming, Nevada, and Arizona.
Montana Statewide 3130 - We expect this talk group to become more active as more DMR repeaters within Montana are installed and connected to BrandMeister. Assuming the other repeater operators chose to participate, this talk group will be static on all BrandMeister networked repeaters within Montana. It is the talk group to use for conversations with other Montana hams that are on repeaters that are not part of MPRG. If you place a call on Montana Statewide 3130, you will be heard on all BrandMeister networked DMR repeaters in Montana, including MPRG repeaters.
MPRG1 31301 - Mac Pass Repeater Group repeaters are static on this talk group. Currently, this includes the DMR repeaters at Mac Pass, North Hills, and Boulder Hill. This is for Helena-area conversations that aren’t meant for a Montana-wide audience. Similar in behavior to Montana Statewide, if you transmit on this talk group on one of the MPRG club DMR repeaters, you will be heard on all of the other MPRG repeaters.
Local 2 - This talk group works only on the one repeater that you are operating on. It is never networked to other repeaters. If you are conversing with hams that are all on the same repeater, consider using this talk group. It is very efficient because you can have a Local 2 conversation on every repeater. In the case of MPRG, that means three different groups of hams in Helena can each have their own separate conversations on the three MPRG repeaters at the same time.
Canada wide 3026 - This is one of many country-specific talk groups, similar in function to USA wide.
A more complete list of talk groups is on this downloadable document from BrandMeister.

If it wasn’t clear before, this is a reminder that
talk groups keep users separated from each other too. If you are monitoring and talking on USA wide, another ham that is monitoring Montana Statewide doesn’t hear your conversation, even though both of you are operating on the same repeater. If there is activity on Montana Statewide, I won’t hear it because my radio is set to MPRG1.
There is such a thing as talk group scanning. This allows you to monitor for traffic from several talk groups, as determined by a scan list that you create and program into your radio. DMR lets you hear as much or as little as you want and your specific interests can be fulfilled while another ham monitoring the same repeater with very different interests hears exactly what they want.

Static talk groups are always-on in that if there is activity on that talk group, it will be transmitted on its assigned time slot, if that time slot is idle. As an example, if there is activity on the Montana State wide 3130 talk group on a BrandMeister repeater in Billings, that activity will be transmitted on time slot 2 of all three MPRG repeaters. If, there is an active conversation on Local 2 talk group on the North Hills repeater, then that Montana Statewide activity from Billings will only be heard on the Mac Pass and Boulder repeaters.

Scheduled Static talk groups come on as static during a set time established by a repeater sysop. At all other times, the talk group operates dynamic. So far, the only scheduled static talk group on the MPRG system is on the North Hills repeater for the Saturday morning net on the WorldWide 91 talk group.

Dynamic talk groups are active only if a user on a given repeater bumps/kerchunks that talk group. Then, it is active for only 15 minutes starting from the end of the last local transmission. As an example, USA wide 3100 is probably active right now as you read this. But, you won’t hear any of that activity until you select USA wide on your radio and briefly press PTT. Then, the BrandMeister server knows to send USA wide traffic to time slot 1 of the repeater you just kerchunked. If you do nothing but monitor the USA wide activity, that talk group will time out in 15 minutes, requiring another bump from you to continue monitoring. If you join in the activity on USA wide, then that talk group will remain active on you repeater until 15 minutes after your last transmission.

This static/dynamic configuration of talk groups is done in the
BrandMeister Master server that our three repeaters are logged into. We are logged into Master 3102, which serves Central USA located repeaters.

We conform to the BrandMeister convention of organizing talk groups so the local groups are on time slot 2 and the DX talk groups are on time slot 1. Please click on the Talk Group Plan tab to see the current plan as developed by the MPRG Chamber of Deputies.

Now that you understand talk groups, here is the not so secret secret that makes BrandMeister a great DMR repeater network for traveling hams. The MPRG talk group plan that you just looked at is not a limitation as to the talk groups that work on our DMR repeaters. The static talk groups listed in the plan work exactly as listed (always-on on a specific time slot) but any other BrandMeister talk group will work dynamic on either time slot. As an example, New Mexico Statewide 3135 is not listed but if you program it into your radio on a channel that has the North Hills repeater frequency pair, color code and with time slot 1, you can talk all day to your buddies in Albuquerque while you are located in Helena. Part of the secret is you could activate New Mexico 3135 on time slot 2 and it will work just as well but we are hoping that you leave slot 2 for us locals and instead use time slot 1 for your DX traffic.

---------------Portions of the page below (grayed out text) is still being written------------

Layers
baseband
represent baseband digitally and in this case, with a tiny number of bits per second
modulate radio signal
time slots

networking/networks
proprietary IP commercial technology for 15 repeaters
commercial bridging for Trbo, P25, analog, consoles c Bridge
DMR-MARC
DMR+
Brandmeister
Network
Tools: Last Heard, Hose Line

Distance Limit
- Not often discussed but there is a 150 kilometer/93.2 mile distance limit when operating DMR on a repeater. This is not an issue for Part 90 DMR users but we hams attempt DX contacts with all of our technologies so you need to know about this limit. Review: Your radio transmits for 30 ms then the mobile radio on the other time slot transmits for 30 ms. The repeater, via its transmitted signal is the timing master. What happens beyond this distance is your transmitted signal shows up late at the repeater and clashes with the signal transmitting on the other time slot. This limitation does not apply to simplex operations because time slotting exists only on a DMR repeater. The specific damage that occurs when you transmit when beyond 93.2 miles from the repeater, we don’t know for sure.


Operations (programming and using your radio)


So you ordered a DMR radio and are waiting for it to show up. You can take the first step now, obtaining a Radio ID. No need to wait for the knock on the door. Actually, there is no need to wait until you are a radio owner. If you have a strong interest in DMR, you can take the first step now.

Step 1: Get a Radio ID number from DMR-MARC: http://www.dmr-marc.net/contact.html
DMR-MARC is the keeper of the world wide numbering plan for ham radio DMR. It is a well thought out plan for subscriber equipment, repeater, and talk group numbering. You can participate in this cooperative effort by obtaining from DMR-MARC the Radio ID for your new DMR radio. Yes, on BrandMeister, you can get away with making up your own Radio ID as long as it doesn’t clash with an already used number. If your DMR repeater is not connected to any of the world wide networks, then you can do as you wish regarding numbering. But, by participating, you can be assured that your Radio ID number is unique in all the world and that there won’t be any ID clashing as you operate on different repeaters that are attached to different DMR networks.

Step 2: Install the Customer Programming Software (CPS) in your computer. For Tytera, CPS and firmware download source is explained on the Resources & Links page. For Hytera and Motorola owners, your dealer is the provider of CPS.

Step 3: Obtain a sample codeplug (radio programming file) from a local source for your model of radio. Make the one mandatory change, change the Radio ID to your ID number, then other changes as you see fit.

Step4: Write the codeplug to your radio.

If you are creating your own codeplug from scratch, or you are a visitor adding our sites to your radio so you can operate on our repeaters while traveling through the Helena area: Please note on the talk group plan that there are three talk groups assigned to TS 2. Those three plus TG 9 for reflectors are the only talk groups that we want on TS 2. All other talk groups, please configure for operation on TS 1. BrandMeister networking allows for any talk group number to work dynamic on either time slot so the only control over this is within your radio programming. We have no ability to restrict talk groups or time slots but we trust that you will be a responsible user of the flexibility and power that BrandMeister brings to ham radio DMR. Please work with us and configure your DX talk groups for use on TS 1. Visitors are welcome to establish communications with their home town via their home town talk group as long as you do it on TS 1. We support TAC 310, 311, and 312 on TS 1 so those are available for reaching out to your home DMR repeater that is not on BrandMeister.



Simplex Programming and Operations. You would think simplex UHF operations would be easy, but it is not, for two reasons. (add two reasons here). What we have settled on we think makes sense and we encourage the adoption of 441.0 MHz as a national simplex frequency for all digital modes including D-Star, DMR, P-25, Fusion, NXDN, and any other future narrow band digital modes.

Frequency: 441.0000
Color Code: 1
Time Slot: 1
Talk Group: 99

Note that outside of our area, Western Montana, the frequency/CC/TG for DMR simplex may be different.
Reminder: Time slots exist only with repeater operations. You can’t have two simultaneous conversations on one simplex frequency.

Repeater,

Hotspot

Voice Communications

GPS Position Reporting. Among other features, DMR supports GPS position reporting. This was created for the Part 90 world, not ham radio. There is no provision for sending your ham radio call sign along with your position report so unlike with APRS, Part 97 ID requirements are not being met if your radio is making periodic position reports and you are otherwise not conversing and saying your call sign at the required times. Please take this into consideration if you activate GPS position reporting in your DMR radio and take action to stay in compliance.

Each DMR radio vendor has their own format for GPS position reporting. This is not an issue for Motorola, Hytera, and Tytera GPS-equipped radios because BrandMeister can pass your report to the dstar.su server for formatting and transfer to APRS. Step 1 is common to all three brands, setting up your call sign, SSID, and symbol that you want to appear on APRS.

Step 1: Go to the dstar.su self-care web page
https://www.dstar.su/selfcare/ and register. Once you are on the main self-care page, select Ham DMR. They need to know your radio brand, position reporting interval, desired SSID to go with your call sign, APRS symbol, and DMR Radio ID. If you are not experienced with APRS, we suggest an interval no less than every 3 minutes and just your call sign without dash anything.

From here on are radio specific instructions.

Step 2 - 9 for Motorola:
The screen shots below are from an XPR 7550 with working DMR to APRS position reporting.

  • We suggest configuring one of your soft buttons as GPS on/off. In addition to giving you the ability to turn off position reporting, this helps control battery life reduction caused by an active GPS receiver.
  • In the Motorola CPS, in General Settings, GPS box is checked.
  • In Network, Services, ARS Radio ID: 310999
  • In every channel page where you want GPS Position reporting to work:
-------------UDP Header Compression: DMR Standard
-------------Text Message Type: DMR Standard
-------------ARS: On System/Site Change
  • In the roam list, in every channel, GPS, ARS: On System/Site Change










Step 2 - 9 for Tytera MD-390: The screen shots below are from an MD-390 with working DMR to APRS position reporting.



Text Messaging
. This DMR feature allow you to send a text message to any Radio ID that is on a BrandMeister-networked repeater. You need to know the destination Radio ID number to send one. Most radios allow for selecting an address book entry for this. Given that the procedure for sending a text message is specific to each model radio, we are not going to try to explain how to do so here. Just like with GPS position reporting, your call sign is not sent with a text message so you need to take some kind of action to insure Part 97 identification compliance.

Reflectors
In Ham Radio DMR, from our prospective on the BrandMeister network, a reflector is a cross-connect between the different networks. To communicate through a reflector from one of our DMR repeaters, you need to have a channel in your radio with TG 9 on TS 2.

To initiate a connection through a reflector: From an idle state, manually place a call to one of the talk-groups on this list: http://brandmeister.ca/brandmeister-reflectors-talkgroup-mapping/ You will hear a voice response that your connection is successful. Switch to your TG 9 channel then initiate your conversation. Note that this connection will remain active until you manually disconnect.

To disconnect: From an idle state, initiate a manual call to 4000. You are disconnected if you hear the voice response that says you are disconnected.

As you make use of this capability, please remember that it uses TS 2, which is the same time-slot that all of the local talk groups are on. If the talk-group on the other end of the reflector connection is busy with conversations, then Montana and MPRG1 may not be available to us for the duration of the reflector activation. It is the design of the reflector system that reflector calls are sent to our repeater on TG 9 TS 2, there is nothing we can do about changing time slots.


Terminology

All Call - One of the three types of calls your DMR radio can place. An All Call is a one-way transmission that will be heard by all radios that are monitoring the time slot that the All Call is placed on. Typically, this feature is used to make announcements of interest to all operators monitoring a given repeater. The latest MD-380 sample code plug has a channel in the MPRG zones for All Call 1 (time slot 1) and All Call 2 (time slot 2). If you want your announcement to be heard by all DMR stations monitoring a given repeater such as Mac Pass, you will have to make the announcement twice, once on each time slot.
Codeplug - The radio programming file generated by the Customer Programming Software (CPS). This file contains the radio-specific information including a Radio ID, frequencies, zones, talk groups, and so on.
Color Code - Analogous to CTCSS, PL, DPL, NAC, DSQ, and so on. This allows for reuse of frequency pairs while keeping the user of one repeater from being heard on another repeater sharing the same frequency pair. MPRG reuses UHF frequency pairs so as not to hog valuable spectrum. As an example, the MPRG DMR repeater at Helena North Hills expects to see Color Code 1 from its users while the MPRG repeater at Missoula University Mountain, which is on the same frequency pair as North Hills, is set up for Color Code 2. As you drive from Helena to Missoula, if you are operating on North Hills, while you are in the overlapping coverage of the two repeaters, only North Hills will repeat your transmission. University Mountain repeater will ignore your transmitted signal because your mobile radio is sending Color Code 1 instead of 2. Valid values are 1 to 15.
CPS - Customer Programming Software (CPS) is the software provided by the radio manufacturer to program all aspects of your DMR radio including frequencies, talk groups, zones, channels, and so on. Also obtained from the radio maker is a programming cable, typically USB on the computer side.
Group Call - One of the three types of calls your DMR radio can place. This is a call to a specific talk group number so that members of that group can hear you calling. A group call may be limited to one repeater or it might be networked to multiple repeaters.
Hot Spot - A single-frequency, very low-powered, very short-range device to allow you to communicate on a DMR network. Originally developed for D-Star, it is now popular in the DMR world to allow those of us not in range of a DMR repeater to communicate on one talk-group. Examples include DV4mini, DVMega on Pi, and openSPOT.
Parrot - A private call to 9990 plays back your transmitted audio. Ham radio needed this 25 years ago, a way to hear yourself talk but nobody else hears you. This is a great feature to test your transmitted audio to figure out a good mic to mouth distance or to test your radio if you receive a too low/high audio complaint. We use it to test for coverage when there is nobody around to talk to. Typically, Parrot is an entry in your Digital Contacts (address book) but it can also be set up as a channel for easy frequent use.
Private Call - One of the three types of calls your DMR radio can place. This is call to a specific Radio ID number. Used when you wish to speak to a specific person and not a group. Private Call is a great way to find somebody when you don’t know what talk group they are monitoring. It can be an efficient way to communicate because at most, you tie up a time slot on two repeaters.
RDAC
- Repeater Diagnostics and Control (RDAC) software is used by repeater owners to remotely monitor and control their repeaters. Monitoring includes things like PA temperature, power output, supply voltage, and received signal level. Control includes changing transmitter power from high to medium and changing channels from mixed mode to fixed analog or fixed digital. This is not something a regular system user will have but if you hear the repeater owner talk about RDAC reporting high SWR, you now know what they are talking about.
Talk Group - A talk group is a logical grouping to enable communications among the radios of a specific group of radio system users. Please see the big explanation toward the top of this page under Academics.
Time Slot - A single DMR repeater supports two simultaneous conversations because its receive and transmit is divided into two time slots, each 30 ms long. Your radio transmits and receives on just one of the two time slots, leaving the other time slot available for another user. In the channel programming of your radio, you select time slot 1 or 2 as appropriate for the talk group for that channel.
Zone - Not specific to DMR but is something you see in DMR radio programming. A zone is a group of channels. It is a way of organizing channels into some kind of group that makes sense to the radio operator. For example, all of the channels for a given repeater site might be put into one zone. Then, a zone equals a site. This is organizing for the human operator, it is not a limit of radio programming. A single zone could contain channels that span multiple sites and could include channels that are DMR and some that are conventional FM. Some radios such as the Tytera MD-380 limit each zone to 16 channels, which matches the number of positions of the top rotary knob. Other radios such as the Motorola XPR 7550 allow a large number of channels per zone.



Lookout Pass, an MPRG FM-only repeater site