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.  Authorized talk groups for use on SCHEART DMR are listed on the SCHEART web site at www.scheart.us  under the Digital drop-down tab.  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: SC CALL, PRN CHAT 1 and PRN CHAT 2.

Operationally, stations should use the talk group that impacts the fewest repeaters for extended conversations.  The PRN talk group activates over 60 repeaters and is great for initial contact and 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 PRN Chat talk group.  Two Chat talk groups are provided: PRN Chat 1 and PRN Chat 2.  These are dynamic talk groups that do not have any repeaters connected full time.  Only stations that activate the PRN 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, moving frees up the PRN channel. When finished, select the Clear Timeslot talk group and key your transceiver.  This action will cancel the talk group on the repeater.  If you fail to clear the time slot, the connection remains active for 15 minutes or longer if there is activity. 

CLEAR TIME SLOT- This talk group is used to clear your connection when using PRN CHAT 1 or 2.  If you do not clear these talk groups after you connect, the time slot will continue to carry their audio for 15 minutes and can interrupt conversations on the local talk group.

ECHOTEST- This talk group provides an option for users to test their signal and audio quality into the system.  A user pushes PTT and when they receive a talk permit tone, can send a voice message.  After releasing the PTT switch, the system will echo back your transmission.  This talk group may be unavailable when the system is in the emergency operation mode.

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. The SC Call talk group uses time slot 1 and is similar to PRN talk group except it only operates on SCHEART repeaters.  SC Call traffic is broadcast on all SCHEART repeaters with the following exception: 1) the repeater is busy with Local talk group traffic or 2) the repeater is busy with PRN CHAT 1 or 2 traffic.  A hold off timer prevents SC Call traffic from interrupting ongoing conversations for 5 minutes on those repeaters.  SC Call talk group is to establish an initial contact and short conversations within the state.  For long conversations, please move to either PRN Chat 1 or PRN Chat 2 talk group.

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 SCHEART repeaters.  No traffic is routed to repeaters outside of South Carolina.  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

Clear Timeslot

27000

2

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 – NC SEOC

SEOC control

1

SC Call

27510

1

Chat 1

27501

1

Chat 2

27502

1

Clear Timeslot

27000

2

* 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

Anderson

444.5375

449.5375

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

442.3875

447.3875

Chester

440.5750

445.5750

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

448.1625

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

Lugoff “

441.8000

446.8000

Murrells Inlet

441.8875

446.8875

Myrtle Beach

441.9125

446.9125

Orangeburg

440.5875

445.5875

Pickens

442.3125

447.3125

Rock Hill

440.5125

445.5125

Spartanburg

440.6625

445.6625

St George

440.6500

445.6500

Sumter

442.3125

447.3125

Sumter Downtown

441.8375

446.8375

Walhalla

442.5375

447.5375

Trailers & Portables

 

 

Aiken Cnty Trailer

440.8

445.8

Field Com Units

440.8

445.8

SCHEART trailer

440.8

445.8

 “- SCHEART partner repeater

Emergency Trailers will only be available on the network during exercises or a response event. They are not normally connected to the network.

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