DMR - Digital Mobile Radio

Talking around the world with just a Tech license and an HT:   A DMR HT Radio allows one to connect to a DMR repeater.  DMR repeaters are interlinked with other repeaters around the world allowing one to talk to other hams virtually anywhere.

In the Tallahassee area there are repeaters (NX4DN) located at Greensboro in west Gadsden county near I-10  at 300 feet, a repeater in Tallahassee located downtown at 200 feet, and a repeater located in Metcalf on a tower at 1,000 feet.  All sites are networked together.  In addition to regional Talk Groups (TG), there is a local TG 9 talk group on each repeater and a local NX4DX network TG 2 talk group that activates on the 3 local repeaters in unison. The NX4DX DMR repeaters do not use K4USD (as noted on RadioId.net), rather the run their own c-Bridge:  http://C-Bridge.nx4dn.org:42420

The NX4DN DMR Repeater Configuration obtained from RadioId.net:

======== Metcalf, GA ========

Callsign: NX4DN 

Frequency: 444.13750 

Offset: +5.000 

Color Code: 1

======= TLH Downtown ======

Callsign: NX4DN 

Frequency: 443.13750 

Offset: +5.000 

Color Code: 1

============= Greensboro Interstate-10 ========

Callsign: NX4DN 

Frequency: 444.98750 

Offset: +5.000 

Color Code: 1

########### TALK GROUPS ###############

The NX4DN Tallahassee DMR Repeaters have the following Talk Group configured.  Only these TG and corresponding Time Slots (TS)  are assessable from these repeaters.  There is no Parrot Talk Group (public or private).

TS 1 TG 3 North Amer

TS 2 TG 3174 SE Regional

TS 2 TG 3112 Florida State wide

TS 2 TG 2 Local Network

TS 2 TG 9 Local Rptr

TS 2 TG 310 

TS 2 TG 3172 NORTHEAST REG

TS 2 TG 31121 FIRST COAST

TS 1 TG 311307 KINGSLAND GA

SUGGESTIONS FOR GETTING STARTED ON NX4DN

Note: Tier 2 repeaters have two time slots: TS1 & TS2 (also referred as "Repeater Slots").  This in effect can make the DMR repeater act like two independent repeaters.  Additionally, all above repeaters use Color Code (CC) 1.  The Color Code acts like a Tone Squelch activating the DMR repeater for use.  The example below uses the open source project OpenGD77. OpenGD77 provides a greatly, greatly, (emphasized greatly) improved firmware and programming CPS software (See https://opengd77.com for details).  The OpenGD77 CPS program utilizes TG Lists and TG override TS settings.  As illustrated below, this hugely simplifies creating a CodePlug.  Many CPS CodePlug programs do not have these features, but a work around is provided below. 

1. Enter DMR ID and Call Sign

   • Using the CPS programming software enter ones DMR ID and Call Sign

     • One can apply for a DMR ID at https://www.radioid.net

2. Create Digital Contacts: Using the CPS software, enter the above 9 TGs as Digital Contacts, and select the override TS = 1 for the two TGs configured for TS1 use.  

   • All TGs can have assigned override time slots, but since TS2 is used by most TGs, setting the repeater default to TS2 will define the TS used unless a TG has an override TS.

   • Also note that one can abbreviate names, but it is strongly suggested to keep the TG number (i.e., "TG 3112 FL SWide").

   • If ones CPS program does not implement an override TS in each digital contact setting, then ignore.  

3. Create Talk Group Lists: Add/create a Talk Group List named "NX4DN", select and add the 9 NX4DN TG contacts to the "NX4DN" TG List. 

   • If ones CPS software does not implement Talk Groups Lists then a seperate channel will need to created for each repeater and TG combination (see step 4 note below).

4. Create Digital Channels: 

   • Configure each repeater channel with the repeater's configurations (Name, RX Freq, TX Freq, CC, TS, & TG List).  For the 3 NX4DX repeaters, you will only create 3 digital channels.

     • Mode:"Digital", Name:"TLH-NX4DN",  RXFREQ:"443.1375", TXFREQ:"448.1375", TGLIST:"NX4DN", RepeaterSlot:"2"

     • Mode:"Digital", Name:"MET-NX4DN",  RXFREQ:"444.1375", TXFREQ:"449.1375", TGLIST:"NX4DN", RepeaterSlot:"2"

     • Mode:"Digital", Name:"GRN-NX4DN",  RXFREQ:"444.9875", TXFREQ:"449.9875", TGLIST:"NX4DN", RepeaterSlot:"2"

       • Note: without TG Lists, one would create a digital channel for each TG. For the NX4DN repeaters, this results in the need to create 9 TGs * 3 Repeaters = 27 digital channels rather than just the 3 channels utilizing TG Lists.   

5. Add Analog Channels: 

   • • Mode:"Analog", Name:"TLH-03",  BandWidth:"25", RXTone:"94.8, TXTone:"94.8"

     • ...

6. Create Zones:  Add/create the Zone "Analog" and another Zone "Digital".

   • Add the 3 NX4DN channels to the "Digital" Zone

     • Without TG Lists, one would typically create a zone for each repeater in order to provide some sense of organization of the plethora of channels needed without TG Lists.

   • Add all analog channels to the "Analog" Zone

7. Write CodePlug to Radio and give it a test.  After writing the CodePlus to the radio, select the "Digital" zone and then a channel such as "TLH-2".  Then scroll through the TG List selecting a talk group like "TG 3112 FL SWide" and call out for a radio check.  You should now be on the DMR airways.  

ADDING DMR PEER to PEER (AKA Simple Xchange)

DMR Community Recommended for Peer to Peer Frequencies

• UHF: 441.000 MHz, 446.500 MHz, 446.075 MHz, 433.450 MHz

• VHF: 145.790 MHz, 145.510 MHz

Use: TG99; CC1; TS1; Admit Criteria:Always; InCall Criteria:Always(or TX)

1. Create Peer to Peer Talk Group

   • Name:"Peer to Peer", TGID:99, CallType:"Group Call"

2. Add 6 P2P Digital Channels

   • Mode:Digital; Name:"P2P 441.000", TX:441.000, RX:441:000, CC:1, TS:1, TG:"Peer to Peer" 

   • Mode:Digital; Name:"P2P 446.500", TX:446.500, RX:446:500, CC:1, TS:1, TG:"Peer to Peer" 

   • ...

   • Mode:Digital; Name:"P2P 145.510", TX:145.510, RX:145:510, CC:1, TS:1, TG:"Peer to Peer" 

3. Create Zone

   • Create a new Zone Name:"Peer 2 Peer" and add the 6 P2P Digital Channels to the new Zone.

4. Save & Write CodePlug to Radio