We am going to share some general information about DMR (Digital Mobile Radio), digital radio system, to provide basic information on what starters need to do and be careful about so the wide range network operation will not be interrupted. I will start with some technical information to be followed with the former.
What is Digital Radio and DMR?
DMR is short for Digital Mobile Radio, which was initially established for commercial use, due to its advantages and ability to use internet infrastructure providing easy access to long distance communication, has been a digital radio system favored by many worldwide. Digital Radio System first transforms the voice to digital data. The transformed voice is of high magnitude to preserve quality. As the data is not possible to be delivered in real time the digital data of the voice is coded through CODEC software. In short it is compressed according to a set algorithm. (Compressing folders in zip/rar format is a similar operation.) Later the compressed data is transformed once again to enable repair of data in case of error that may occur while transferring via air and with the addition of necessary information will be delivered to the receiver through digital modulation techniques.
The basic advantage of DMR system is the 2 channels it offers from a single frequency with the help of a duplexer and roll, as it has a TDMA (a.k.a Time Division Multiple Access). This system is the same as the one used by 2G mobile phones. It delivers 4800 symbol/second core data via air. As it uses 4fsk modulation this speed is calculated as 2 bites per symbol and theoretically there is a transfer of 9600 baud data. (in reality it is even less.) As you can see, with the help of modern coding techniques a system such as DMR can operate at a speed which is extremely elemental for computers.
Some basic terminology
CC: Color Code. This code is the equivalent of CTCSS tone of the analogue system for the DMR digital system. It must pair off in order to reach a roll or make a call to a simplex. CC:1 is mainly used by amateurs.
TS: Time Slot. The major difference of DMR system from other systems is that the same roll can be used by 2 different user groups simultaneously. In short 2 people can communicate on a single roll at the same time. The frequency divides into two temporally. Each of these divisions is called Time Slot. In order for you to communicate the time slot needs to pair up. Due to the inconsistency of some devices in the market, such as TYT-MD398 which fails to provide the necessary support due to design errors there may be communication breaks. This device should not be used. Simplex uses TS:1 for communication.
TG: Talkgroup. Talkgroup is one of the most significant qualities that differentiates digital system from the analogue. In order to communicate with a station anywhere in the world all you need to know is their talkgroup so long as you have a roll included in an international network. In a talkgroup programmed on a regional roll or hotspot, once you press the latch on your roll the frequency of the other party will link the two rolls to each other may it be CC, TS or whatever and manage a two-way communication until the latch is set free and communication is terminated. In that sense we can think of it as tunnels over the net. Using the same frequency you can communicate with others just on TG, users can form communication groups amongst each other even if they are CC, TSs. for local communication the roll needs to be on 9 and for simplex communication needs to be 99. Please do not use TG91 or random TG. For example on TG91 DMR-Marc system Worldwide, means the whole world. In BM system it is defined locally. For local communication the DMR ID is used. You would not want to engage over a thousand rolls just to communicate with an amateur in your city. You can encounter unpleasant reaction within a short time.
RX List. While the delivery talkgroup on the channel you are is stable, different talkgroups can be added to the lists and followed over the same channel. The Rx lists can be formed and then programmed according to channel later on. If you do not program the Rx list for the channel it will only broadcast the communication of the talkgroup it delivers.
Digital Contacts: It can be considered as an address book. The IDs and TGs to be used needs to be recorded here. There are 3 basic contact types.
Group Call: You need to add your Talkgroups as such. Later on when the channel is to be programmed it will pick from this list.
Private Call: Personal IDs for Turkey that begin with 286 in case you enter the IDs here the call sign or name of the contact will appear on the screen.
All Call: It is a call made to all the system skipping the Talkgroup. This should NEVER be used unless for real emergencies.
Zone: This is one of the part that you need to be most careful about in radio programs. You may add 1000 channels to the digital radio but unless you add them to Zone you cannot use any of them. When you roam radio channels like you did before you are not roaming the recorded list but the dedicated Zone channels. You can adjust them according to your personal choice. In many models 16 channels are permitted per Zone, although you can add the same channel to several zones.
What to do when you buy a new DMR radio:
We are now at the point on how to form a channel. Let’s do it step by step
- If you do not have one, you need to issue a DMR ID from this link: https://register.ham-digital.org. This ID is matched with your call sign, a digital ID that begins with 286 for Turkey. If there are no problems with your documents, you entered your information correctly it will be approved within a few days time. You should never use someone else’s ID unless by mistake.
- You turn on your radio, and put the information on the register/calibration information etc. as you take back-up of the information and get to the Basic Settings/General Settingstab and put the number on the “Radio ID” section. Mind you don’t write it on the Serial ID section.
- On the Radio Name section, “TA1MD Mutlu” etc. write your call sign and name. In some new version devices this name is submitted to the contact automatically. In short even if you are not listed with the contact your call sign and ID appear along with your name on your contact’s screen.
- TX Preamble Durationthis is an important parameter for digital communication. Although it may slow down your communication at first it is important to have for the roll to catch your signal in cases of weak signal conditions. Set it to 200-300 on the scale. If you have difficulty in accessing the roll slowly increase the setting. 5. You can set the other specialties according to your preferences.
It is time to set a channel. Let’s do it step by step
- We add the Talkgroup(s), Contacts/Contact Listetc. as “Group Call” into the list. Make sure you choose Group Call.
- If we wish to contact more than one talkgroup in any channel we get in the Rx list menu and form a list or add the TGs we formed in the first step. Listing rank is not important.
- We form a new Channel from the channel menu. We name the channel and enter the information of: rx tx frequencies, CC, TS.
- We choose the Talkgroup we want to contact from the Contact Name section. You will see individual names here. If you choose an individual name, once you press the latch you will have only contacted a single person (an individual call).
- Choose your list form the Rx Listsection. Choose Privacy OFF / None / Disabled. Choose “Always” in the Admit Criteria section. This way even if there is a station broadcasting through the network in the channel you can easily go through it with the roll locally. However make sure you don’t interfere with other channel’s communications. If the roll is not connected to the web or you are using simplex frequency it is better to chose “Color Code”.
- You will see several options related to digital systems on the screen, I will be providing more information on these in my next article.
- Then you click the Zone window once you have saved the prior actions. Here all zones organize channels according to choice and finally your channel is ready to use.
Additional settings and Useful information
The following additional settings are seen on the channel parameters of the device.
Auto Scan: It is the automatic scanning specialty of the device for the scan list programmed. Let’s say there are 3 channels which you follow regularly. Say you want to scan these channels but you did not fancy getting into the menu to start the scanning option or use the side buttons to scan. You can create a new channel and choose auto scan. Once you open the channel the device will automatically scan the programmed list.
Rx Only: informs that the device cannot use Tx in the channel. In the digital system even if you press the latch for a second the ID is on screen and if there are channels you just listen to you need to click on them.
Lone Worker: The device will ask you o click the button periodically and will set an alarm in case you don’t. Do not activate this function. VOX: Defines whether the channel will have the voice Tx specialty or not.
Talkaround: provides the option to enable communication with users of the roll in your vicinity and enable contact without occupying the others on the roll through the signal sent by the roll delivery frequency. It provides the chance to communicate without changing the frequency in cases when the roll is not receiving signals.
Send/ Receive GPS: Defines whether or not to deliver location if the radio has GPS. Do not use this function unless you have completed GPS settings carefully.
Private Call: The specialty to communicate privately with another user on the channel.
Private Call Confirmed: Checks whether the device is on the channel or not before transmitting individual calls. If there is no signal from the contact radio then it does not allow delivery in vain.
Emergency Alarm ACK: the warning signal by the radio in case a user in the channel broadcasts an emergency call. It will be good to have it on you may receive a signal from someone in need of help one day.
Emergency System: it is the setting that defines how the emergency call sender radio will act in case of an emergency situation. You can leave it off for now as there is no agreed upon system. It can be highly disturbing in case used incorrectly.
TOT: the time set to prevent any occupant use of the channel and malfunction of the radio in case the latch is left pressed or there is a problem in the head-set. A 45-60 second timing should suffice.
TOT Rekey: If you set it on 3-5 you will have taken the precaution for cases of contact loss.
Compressed UDP Data Header: It is connected to the roll or network moderator. You need to ask him.
Privacy: It is a basic crypto mechanism. While it does not provide security at all unless for some devices that are issued upon private license it does not hide your ID either. It should be Disabled, it is not suitable for usage.
GPS System: you choose which setting to use in cases where the GPS is on.
Talk Permit Tone: Once you contact the roll and receive the authorization to broadcast by the roll the device informs you with a signal. Not speaking unless you hear the signal will prevent your communication to be partially transmitted or not transmitted at all.
Channel Free Indication Tone: As there is no tail tone in digital radios it may be difficult to understand when the other party lets go of the latch. Therefore the radio informs you that the transmission is complete with a signal.
Group/Private Call Hang Time: When you receive a call, in case you press the latch within the time set to answer you will have made a call to the TG or user who has made a private call to you. In network connected rolls if the private call time is set long and the group hang time is set to 0 then confusions could be prevented. In other case say that there are two amateurs that are QSO’ing abroad, and you need to QSO. In case there is group hang time on your device you will have to wait for the QSO’ing of the distant devices and some time to follow once they finish so that you can conduct your QSO. Otherwise your device will transmit the information to their group and this will result in failure of communication as well as interference to their transmission.
Radio Disable Decode: Disabling radio remotely. It is a very useful specialty. In case there is a problem on your device, your headset has a problem, the PTT latch is stuck or malfunctioning, your child takes the radio and sings on the roll or you lose the device, you do not need to disable your ID but you can easily turn your device off and on when needed. Such unwanted transmissions are not sent to local roll users but transmitted all over the world interrupting so many people therefore it is more important than ever.
Radio Enable Decode: Enabling the radio remotely. If you also have this setting enable it so if you disable remotely you can enable your device afterwards. In some devices it is activated together with the disable setting.
Remote Monitor Decode: Remote radio setting to listening mode. If you are using your device during mountain climbing or skiing it is especially useful in case you fall, pass-out, have a traffic accident, lose your radio and other emergencies. Your friends who have not heard from you can set your radio to monitoring mode remotely to figure out your status. This can be a life-saver. However it should not be used by amateurs as malevolent people may use it to listen to you. It can be turned off to prevent such problems. You can set the transmission period from Remote monitor duration settings. A period of 30-45 seconds seem to be enough.
GPS (APRS) Ayarı
If your radio has a GPS and supports periodic transmission (although some devices have GPS, it does not), you can have it transferred to the APRS system via a repeater connected to the BM system.
- If you don’t have an account yet visit https://brandmeister.network/ and create.
- After your registration is approved, log in, click on your call sign at the top right of the page and click the “Selfcare” button from the page that opens.
- Select your radio model from Brand section, if you are using brands such as TYT, select “Chinese Radio“. Select APRS Interval 180 sec. Don’t forget to click on the save button after selecting your call sign, message and icon. Do not handle the airsecurity and hotspot security parts, these are systems created to block if someone tries to use your Id or something. If you open it accidentally, you cannot access the network.
- Save the application ID, which you can learn from the repeater responsible operator, as a Private Call under the name APRS in the Contact List.
- Come to a tab from the GPS System menu and select this APRS record in the Destination ID section.
- Select the time between submissions on the Default Report Interval section. Not less than 5 minutes (300 seconds). If it is a stationary station, it should not be less than 30 minutes (1800s). It is useful to keep it as long as possible.
- Select the channel you will transmit from the GPS revert channel section. Select “Current CH” if you want it to be sent on the channel you are on.
- When you select the GPS System number that you have set from the channel parameters page or the radio menu, your GPS will be turned on and will start sending the signal after connecting to the satellite.
We have completed the settings but how do we make a call?
We have successfully completed the settings and uploaded them to our device. How do we do our first test call? Now, one of the important parameters we need to pay attention to when making calls is talkgroup. For our first call, it would be appropriate to use the local tg number 9 tg.
We take our radio to the channel where this tg is and press the PTT. You will see the red light blink at least once on most radios. In the meantime, unlike analog radios, our radio first communicates with the DMR repeater and asks if the channel is available and whether it is allowed to send. If there is an error in your settings or it does not get a positive response, it will quit after a few tries and give you an error tone. If it receives a positive response, the red light will turn on steady and, if programmed, a short talk permit tone will be heard.
Here, after making your normal call, adding talkgroup 9 at the end is a method that has not yet been settled in some countries. If the station to answer cannot look at the screen without releasing the PTT, it may not know where to respond. So, “Is there any station to listen? here a call like TA1MD-tango alpha one mike delta, talkgroup 9 ”makes it easier for the remote operator.
What is Static and Dynamic Talkgroup?
Static Talkgroups are talkgroups that are programmed on the system by the repeater managers and that the repeater will automatically broadcast the calls coming from the internet. For example, 12345 Talkgroup, a statically programmed repeater transmits it as RF whenever someone from TG12345 starts speaking, no matter where in the world. In this way, calls can be made from anywhere in the world to local city repeater, which have already been programmed with TG2860.
The opposite is Dynamic Talkgroup. Dynamic talkgroups remain active for a period of 10-15 minutes determined by the system when there is a signal reaching the repeater via RF. So you wanted to talk to a friend in Belgium.
You have seen the country code 206 by typing Belgium at https://brandmeister.network/?page=talkgroups. As soon as you write this on your device, press the PTT and reach the repeater, the talks in Belgium will start to be broadcast by the repeater you use. As this TG206 is statically programmed in the repeaters there, they will be able to hear you. Since the dynamic tg is temporarily turned on in your repeater, you will also be able to hear them, and thus two-way QSO can be done.
If the country you are calling is a large area with many repeaters and you are going to call a specific person, it would be appropriate to use more local Talkgroups.
Daily use and practical settings
We would like to mention a few points that many people have problems with.
First of all, many people call the repeater ID and normally do not get an answer. I think it’s a habit of staying with D-Star or any other system, but “In DMR system, there is nothing with the user’s repeater ID.” Please forget the repeater IDs forever.
After providing the physical connection to make the call, that is, after entering the frequency, slot and CC information, only the other party’s static TalkGroup is important. The repeater only broadcasts incoming calls to these talkgroups as RF. The tg’s you see here with the blue lock symbol are the Static TGs that are always fixed. If you are going to call a region, you must use one of these. The ones that appear in yellow are Dynamic Talkgroups triggered by an amateur in that area via RF and temporarily opened. Dynamic talkgroups are activated the moment users press the PTT on a tg and close automatically 10 minutes after the last signal.
Contacting the Remote Station
Let’s say you will have a call with Germany, its TG is 262. If you do not know a more regional TG you will enter this in the contact name section of your device. If there is a manual change section, you can also enter it there. As soon as you press the PTT, your repeater starts to broadcast 262 for 10 minutes. Thus, when your friend in Germany answers you again on TG262, you can hear him.
Whichever TG enters the system, that TG exits. Except for very exceptional cases, you should always reply via incoming tg. Reflector etc. systems are not used in our country, so it is best to respond via TG on the screen.
If a person’s ID / Call sign is displayed, but if there is no voice, the problem is in your 99% Rx List. The tg he is speaking to is not in the Rx List programmed for the channel you are on or Rx List is not programmed on the channel. Check these settings.
Source: TA1MD Mutlu Dülger