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Trunked Radio Systems & P25 Protocol
Step through dynamic frequency allocation, P25 control channel TSBK frames, C4FM/CQPSK modulation, and SDR vocoder decoding
FREQUENCY ALLOCATION • STEP 1 OF 6
Trunked Radio Frequency Allocation
Unlike conventional radio where each team stays on a fixed frequency, trunked systems share a pool of voice channels managed by a central control channel that dynamically routes talkgroups as calls begin.
Pool Frequencies
851.0125 - 853.875 MHz
Control Channel
851.0125 MHz (CC)
Allocated TGID
1001 (Fire Dispatch)
Trunking Controller Channel Grant Allocation
SUBSCRIBER (Radio ID 84120) -> PTT Request (TGID: 1001)
CONTROLLER -> Group Voice Channel Grant (Opcode 0x00)
Assigned Frequency: 851.5125 MHz (LCN 121)
Result: 42 Subscribers in TGID 1001 tune to LCN 121
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