In Digital Mobile Radio (DMR), a channel is the complete set of settings that tells your radio exactly how, where, and with whom to transmit and receive. It’s the “operating slot” you select on the radio to start talking or listening.
Think of a DMR channel as a pre-programmed recipe for communication. Each channel combines:
- Frequency (the actual RF channel)
- Timeslot (TS1 or TS2)
- Color Code (like a repeater access code)
- Talkgroup/Contact (who you’re talking to)
- Other parameters (power, bandwidth, etc.)
When you select a channel on your radio, it instantly configures everything needed for that specific conversation or repeater.
Types of Channels
There are two main types of channels in DMR radios:
- Digital Channels (DMR mode)
- Used for digital voice (and sometimes data) on DMR networks.
- Require a talkgroup (TG) or private call ID to work.
- Analog Channels (FM mode)
- Used for traditional analog FM repeaters or simplex.
- Use CTCSS/DCS tones instead of talkgroups.
Most amateur DMR codeplugs have a mix of both.
Key Parameters in a Digital Channel
When you create a channel in the CPS (e.g., OpenGD77 CPS), you set these fields:
| Parameter | Description | Typical Values / Notes |
|---|---|---|
| Name | What shows on the radio display (e.g., “KD2LNB TS2 BM Public”) | Keep it clear and descriptive |
| Rx Frequency | Receive frequency (usually same as Tx for simplex, offset for repeaters) | e.g., 442.0000 MHz |
| Tx Frequency | Transmit frequency (usually +5 MHz offset for UHF repeaters) | e.g., 447.0000 MHz |
| Timeslot (TS) | Which of the two TDMA slots to use (TS1 or TS2) | TS1 or TS2 – must match repeater config |
| Color Code (CC) | Repeater access code (like a digital CTCSS) | 1–15 (most repeaters use 1) |
| Contact / TG | Either a single Digital Contact (fixed TG or private call) or a TG List (multiple TGs) | e.g., TG 91 Worldwide or “BM Public” TG List |
| Group List | (Optional) TG List assigned to the channel (OpenGD77 feature) | Allows cycling through multiple TGs |
| Bandwidth | Channel spacing (usually 12.5 kHz for DMR) | 12.5 kHz |
| Power | Transmit power level | Low / Mid / High |
| Admit Criteria | When the radio allows TX (e.g., Color Code Free, Always, etc.) | Usually “Color Code Free” |
| TX Timeout | Prevents long transmissions | 180–300 seconds |
| Scan List | (Optional) Which scan list this channel belongs to | For scanning multiple channels |
| Rx Group List | (Advanced) Receive-only filtering | Rarely used in amateur |
How Channels Work with Talkgroups and TG Lists
- Single Contact channel (stock firmware style):
The channel is locked to one fixed talkgroup (e.g., TG 91 Worldwide).
You transmit and receive only on that TG. - TG List channel (OpenGD77 style – recommended):
The channel is assigned a TG List (e.g., “BM Public” containing 20+ talkgroups).
On the radio: - You select the channel once.
- You cycle through the talkgroups in the list using left/right arrows or menu.
- Transmit on the currently selected TG.
- Receive only from TGs in the list (plus the current one).
→ One channel can handle dozens of talkgroups — huge efficiency!
Channel Examples from Typical Amateur Codeplugs
- Hotspot Parrot
Name: HS Parrot
Freq: 433.5000 MHz (simplex)
TS: 2
CC: 1
TG List: “Parrot” (usually TG 9990 for echo test) - Repeater Local
Name: KD2LNB TS2 Local
Rx: 442.5000 MHz
Tx: 447.5000 MHz
TS: 2
CC: 1
TG List: “Local Static” (e.g., TG 2 or 3116) - Worldwide
Name: BM Worldwide 91
Rx/Tx: Same as repeater
TS: 1
CC: 1
Contact: TG 91 (or TG List with multiple worldwide TGs) - Analog Repeater
Name: NYC Analog VHF
Freq: 146.5200 MHz (simplex)
CTCSS: 100.0 Hz
Mode: Analog FM
Why Channels Are Important
- Channels = usability — They turn complex DMR parameters into simple selections on the radio.
- Fewer channels needed with OpenGD77 — Thanks to TG Lists, you might only need 1 channel per repeater/hotspot instead of 20+.
- Zones group channels — You organize channels into Zones for fast selection (e.g., “NYC Repeaters” Zone contains all your local DMR and analog channels).
Best Practices for Channels
- Name them clearly — Include repeater callsign, timeslot, and main use (e.g., “W2ABC TS1 TAC310”).
- Use TG Lists — Avoid duplicating channels for every talkgroup.
- Match repeater settings exactly — Wrong TS, CC, or offset = no communication.
- Test every channel — Transmit on Parrot (9990) or a known TG to verify.
- Keep channels lean — Only program what you actually use to avoid clutter.
In short: DMR channels are the ready-to-use operating configurations on your radio. Each one defines a specific frequency, timeslot, color code, and talkgroup(s) so you can instantly switch between local repeaters, worldwide talkgroups, hotspots, or analog FM — all with just a few button presses. When combined with TG Lists and Zones in OpenGD77, they make even a large, complex codeplug feel simple and powerful!