Repeater System/Frequencies & Talk Groups

The DMR repeater system provides amateur radio operators access to a commercial level radio network whose operation is based on talk groups rather than just frequency channels.  Talk groups are unique digital identifiers that help route conversations through the network and into the user’s radio.  DMR repeaters support two simultaneous voice/data conversations on a single frequency pair.  Each repeater is configured to support a full time local talk group and a wide area talk group.  During normal operation, the SCHEART DMR network is integrated with the NCPRN network and the wide area talk group (PRN) covers South Carolina, North Carolina, parts of adjacent states.

To support two simultaneous conversations on the same frequency, the repeater uses Time Division Multiple Access (TDMA) technology. With TDMA, conversations are divided into two time slots and the radio/repeater synchronizes their data depending on which time slot used.  In normal operation, SCHEART DMR is configured to support a local talk group (time slot 1) and a wide area (PRN time slot 2) talk group. Stations on the local talk group hear only local traffic while stations on the PRN talk group will hear any traffic on the multi-state network during normal operational mode.  Additional talk groups are available that share time slot 1 on a dynamic basis.  If a user keys one of the dynamic talk groups, that talk group shares time slot 1 with local.  The following dynamic talk groups are available: TAC 1- English worldwide, TAC310 -North America, and DCI BrandMeister. The BrandMeister talk group provides for interoperability with DSTAR® and Fusion® system.

Operationally, stations should use the Local talk group for all local conversations.  The PRN talk group activates over 60 repeaters and is for initial contact and should be used only for short conversations. If you make a contact with a station on PRN and plan to have an extended conversation, both stations should switch to a Chat talk group.  Two Chat talk groups are provided: Chat 1 and Chat 2.  These are dynamic talk groups that do not have any repeaters connected full time.  Only stations that activate the Chat talk group through a repeater will be connected.  Two stations may move their conversation from PRN to a Chat talk group or multiple stations may move.  In either case frees up the PRN channel. When finished, select the Clear Timeslot channel and key your transceiver.  This action will cancel the talk group on the repeater.  If you fail to clear the time slot, the connection automatically times out after 15 minutes with no traffic on the local repeater.  TAC1, TAC310, and DCI BrandMeister are dynamic talk groups and you must key once to connect. Then you can make a call and converse with stations outside of the Carolinas.  Do Not Activate these talk groups just to listen.  You can find steaming audio available if you just want to listen to talk group activity. When you activate a dynamic talk group you busy up time slot one that local stations may need to use to talk.

SCHEART DMR has two operational modes: Normal Operations and Emergency Operations.  During Normal Operations, all talk groups are available to stations and the PRN talk group covers multiple states.  SCHEART also has a special talk group called SC Call.  This talk group only operates on the SCHEART network.  When using this talk group, key and make your call.  Every SCHEART repeater not currently carrying a conversation on Time Slot 1 will broadcast your transmission.  SC Call talk group is to establish an initial contact within the state.  Please move any conversation to Chat 1 or Chat 2.

During exercises and incident responses, the DMR system may revert to emergency operational mode (EOM).  Under the EOM, the PRN talk group is restricted to only SCHEART repeaters.  The Local Talk Group is not affected but normal dynamic talk groups outside the state are suspended.  Additional talk groups to support mutual aid communications are activated along with a data channel.   Other talk groups may be established by the network administrators as necessary to support the response.  The DMR system will remain open but stations supporting the incident should be provided priority access.  The following two tables describe talk groups in both modes:

Normal Operational Mode:

Talk Group Name

Talk Group Code

Time Slot

Local

27500

1

PRN

2

2

SC Call

27510

1

TAC1

8951

1

TAC310

310

1

DCI bridge

3100

1

Echotest

9998

1

Simplex

99

1 or 2

PRN Chat 1

27501

1

PRN Chat 2

27502

1

 

Emergency Operational Mode

 

Talk Group Name

Talk Group Code

Time Slot

Local

27500

1

PRN -SC Statewide only *

2

2

Data

36102

1

Statewide Mutual Aid **

36104

2

SC Call

27510

1

Chat 1

27501

1

Chat 2

27502

1

* PRN wide area traffic restricted to repeaters within SC.

** Dynamic PTT group

SCHEART  DMR Repeater Information – All repeaters use Color code = 1

Location

Transmit Receive
Aiken * 443.4625 448.4625
Barnwell 440.6875 445.6875
Beaufort 441.9875 446.9875
Beech Island 444.2875 449.2875
Bluffton 444.7375 449.7375
Charleston Downtown 443.0375 448.0375
Charleston North 442.4625 447.4625
Charleston South 443.3875 448.3875
Clemson 442.2375 447.2375
Columbia Downtown 440.6125 445.6125
Columbia East 442.5125 447.5125
Columbia West 443.5375 448.5375
Dillon 443.1625 445.1625
Florence 442.1625 447.1625
Georgetown 441.8125 446.8125
Greenville 443.1125 448.1125
Greenwood 443.8375 448.8375
Hilton Head 442.0375 447.0375
Lake City 440.6375 445.6375
Pickens 442.3125 447.3125
Murrells Inlet 441.8875 446.8875
Myrtle Beach 441.9125 446.9125
Orangeburg 440.5875 445.5875
Rock Hill 440.5125 445.5120
Spartanburg 440.6625 445.6625
St George 440.6500 445.6500
Sumter 442.3125 447.3125
Sumter Downtown 441.8375 447.8375
Wallhalla 442.5375

447.5375

 *- Aiken is connected to the system but configured differently for local and dynamic talk groups. See WWW.NCPRN.NET for specific information on this site.

“- SCHEART partner repeater

*”Aiken is connected to the system but configured differently for local and dynamic talk groups. See NCPRN for specific information on this site.

” Denotes a SCHEART partner repeater

W3KH has written 10 articles

December 18, 1946 - October 12, 2016, SK