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Digital mobile radio (DMR)
By Bernard Falkin, KG6FBM, Updated November 15, 2024
The DMR standard operates within the existing 12.5 kHz channel spacing used in
land mobile frequency bands globally, but achieves two voice channels through
two-slot TDMA technology built around a 30 ms structure.
The modulation is 4-state FSK, which creates four possible symbols over the air at a rate of 4,800 symbols/s, corresponding to 9,600 bit/s.
After overhead, forward error correction, and
splitting into two channels, there is 2,450 bit/s left for a single voice channel using DMR, compared to 4,400 bit/s using P25 and 64,000 bit/s with traditional telephone circuits.
Time-division multiple access (TDMA) is a channel access method for shared-medium networks. It allows several users to share the same frequency channel by dividing the signal into different time slots. The users transmit in rapid succession, one after the other, each using its own time slot.
CDMA is short for Code-Division Multiple Access, a digital cellular technology
that uses spread-spectrum techniques. CDMA does not assign a specific frequency for each user placing or receiving a call. ... TDMA technology divides a radio frequency into time slots and then allocates these time slots to multiple calls.
Introduction to DMR
DMR Repeater ID
registration
Your DMR ID is a 7 digit number.
DMR contact list
Talkgroups
list (virtual radio channels)
AnyTone AT-D578UVIIIPRO Tri-Band Amateur DMR Mobile Radio
ALINCO DJMD5TGP
This is the radio I own, with GPS. You can set the time and date on the radio using the GPS. You can send the GPS data in a text. The radio is dual receive, but only one channel can be heard at a time. The radio has 4,000 channel capability, 250 zones (groups), and 200,000 DMR IDs in the contact list. You can program the two buttons yourself that are located below the PTT, using the software.
Alinco DJ-MD5XLT Dual Band DMR 5W w/GPS Gen 3
Changing DMR Talkgroups (virtual radio channels) on the fly, Alinco DJ-MD5, Anytone D878UV and Side Tone option.
Not only is DMR capable of transmitting voice, but the end-to-end digital nature
of DMR enables data applications such as text messaging, GPS, and telemetry.
Telemetry
https://www.amateurradio.com/how-to-get-into-dmr-without-a-radio/
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Analog
Input Frequency (Offset), Output Frequency, PL
Welcome to the Western States DMR Network
DMR channels
Input Frequency (Offset), Output Frequency, Color Code, Time Slot, and a Talkgroup (virtual radio channels).
Some radios require a receive group list.
In the code plug (the radio file) define your DMR ID and call sign.
Every channel that you wish to have in your radio must be defined in a Zone, like a channel bank. Most radios have 250 zones available. Think of every Zone as a separate radio. One could be used for LA county fire, and another Zone could be used for frequencies when you visit relatives in another state.
Think of a "Zone" as a way to organize a group of channels. For most users there are several talkgroups (virtual radio channels) 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.
Important
Talkgroups (virtual radio channels) 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.
****
Time slots
There are 2 time slots per repeater frequency. Time slot 1 is reserved for
talkgroups (virtual radio channels) that are far away like World 91. Time slot
2 is reserved for talk groups that are local like 310 & CA 3106. Only one
person can talk on a time slot at a time. Many people can listen to multiple
talk groups at a time.
Text messaging
You can send and receive text messages using DMR repeaters. I sent a text
message to a station in Florida and he read it back to me.
Parrot
Eliminates the need for a radio check. However, people ask for radio checks all
the time to start a conversation. Parrot, repeats your voice through the
repeater so you can hear how you sound.
Codeplugs
PAPA Bridge: This talk group bridges to the PAPA D-STAR and analog repeaters.
Now you can talk with your PAPA friends on any repeater.
PAPA Chat: This Static talkgroup links together the PAPA System DMR repeaters.
The place for a QSO with other PAPA people.
Worldwide 91: Links BrandMeister DMR repeaters across the world.
Sound file, China Contact:
https://bit.ly/3gYJxs2
Current DMR Info…
For the most current DMR info, check into the DMR Roundtable, 8pm Pacific time
Mondays on the California talkgroup, BrandMeister TG 31077.
This is the most dynamic part of the codeplug as here you find the radio ID
aliases (Private Calls) and talkgroup numbers (Group Calls).
Simplex
Simplex uses the talkgroup 99 and only time slot one. Transmitting using DMR is
a lot more efficient than analog, the signal goes a lot farther. You can also
send and receive text messages using simplex.
Amateur Radio Notes: DMR - 1
DMR 101
As with most of our radios that can receive frequencies out of band. You can
listen to LA county fire, Sheriff's and other agencies.
HYS
telescoping antenna
DHT Electronics 2pcs RF coaxial Coax Adapter SMA Female to BNC Female
DMR ID Password for a hotspot or
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Other questions:
Are these radios capable of transmitting DMR on FRS/GMRS? Yes, but it's illegal.
Are these radios capable of transmitting DMR on MURS? Yes, but it's illegal.
Can I send a text message to a cell phone? Yes
Do I need a radio to
operate DMR?
No
• Your questions?