1. Introduction and Overview
The DMR818S is a high-performance 2W TIER II digital walkie talkie module designed for long-distance communication. It integrates a microcontroller, digital mobile radio IC, and an RF power amplifier, making it suitable for various embedded applications. All operational parameters, including CTCSS, CDCSS, squelch (SQ), and predefined channels, can be easily configured via a communication protocol.
By connecting an external power supply, speaker, and audio amplifier, the DMR818S can form the core of a professional digital walkie talkie system. Its simplified interface and ultra-small size facilitate integration into a wide range of handheld devices and other communication systems.
The DMR818S-U variant has successfully obtained CE-RED and FCC ID certifications, ensuring compliance with relevant regulatory standards. Two versions of this module are available: DMR818S-NVOC and DMR818S-AMBE.
2. Key Features
- Frequency Bands:
- UHF: 400~470 MHz
- VHF: 134~174 MHz
- 350 Band: 320~400 MHz
- Communication Range: Up to 5 km
- Power Output: Max 2W (high power), 0.5W (low power)
- High Sensitivity: -124 dBm
- Bit Error Rate (BER): Down to 1% under -121 dBm
- Frequency Configuration: Independent frequencies for Transmit (Tx) and Receive (Rx)
- Volume Control: 9 adjustable volume levels
- Bandwidth:
- Analog: 12.5 / 25 KHz
- Digital: 6.25 KHz
- Messaging: Message transmission and reception capabilities
- Modes: Supports DMR (Digital Mobile Radio) and Analog walkie talkie modes
- Data Storage: Built-in EEPROM for data retention even when powered off
- Frequency Stability: 1 ppm TCXO crystal
- Signaling: 51 CTCSS, 166 CDCSS
3. Applications
- DMR walkie talkie module integration
- Invisible intercom systems
- Building security systems
- Audio surveillance systems
4. Specifications
General Parameters
| Parameters | Test condition | Min. | Typ. | Max | Unit |
|---|---|---|---|---|---|
| Voltage range | 3.3 | 4.2 | 5.0 | V | |
| Operating Temperature | -20 | 25 | 60 | °C | |
| Frequency range | @UHF | 400 | 470 | MHz | |
| @VHF | 134 | 174 | MHz | ||
| @350 | 320 | 400 | MHz | ||
| Start time | 2000 | ms | |||
| Uart baud rate | 57600 | bps |
Current Consumption
| Parameters | Test condition | Min. | Typ. | Max | Unit |
|---|---|---|---|---|---|
| Sleep current | CS pulled low for 3 seconds | < 55 | uA | ||
| Rx current | < 135 | mA | |||
| Tx current (high power) | @VCC=4.2V, 2w analog | < 1300 | mA | ||
| @VCC=4.2V, 2w digital | < 1000 | mA | |||
| Tx current (low power) | @VCC=4.2V, 0.5w analog | < 650 | mA | ||
| @VCC=4.2V, 0.5w digital | < 500 | mA |
RF Parameters
| Parameters | Test condition | Min. | Typ. | Max | Unit |
|---|---|---|---|---|---|
| Tolerance of frequency | 1 | 1.5 | ppm | ||
| Modulation sensitivity | 1.5KHz/2.5KHz frequency offset (N/W) | 6 | 7 | 12 | mV |
| Adjacent-channel power | @12.5K offset | -60 | -62 | dBm | |
| Mic input voltage | 0.1 | 1.6 | Vpp | ||
| CTCSS modulation frequency offset | 0.35 | 0.4 | 0.6 | KHz | |
| Modulation characteristics | 300HZ | -13 | -11 | -9 | dB |
| 500HZ | -9 | -6 | -5 | dB | |
| 1000HZ | -3 | 0 | 1 | dB | |
| 2000HZ | 3 | 6 | 7 | dB | |
| 3000HZ | 5 | 7 | 11 | dB |
Rx Parameters
| Parameters | Test condition | Min. | Typ. | Max | Unit |
|---|---|---|---|---|---|
| Sensitivity | Analog (12db SNR) | -120 | dBm | ||
| Receiving BER (DMR modulation) | @ -118dBm | 5 | % | ||
| Audio output amplitude | 500 | mV | |||
| Audio Output impedance | 30 | KOhm | |||
| Adjacent channel selectivity | Offset:+12.5KHz | 60 | dB |
5. Pin Definition
The DMR818S module features 20 pins for various inputs, outputs, and power connections. Refer to the table and diagram below for detailed pin assignments and descriptions.
| Pin NO. | Pin name | I/O | Level standard | Description |
|---|---|---|---|---|
| 1 | MIC_IN | I | Microphone or line in | |
| 2 | UART-TX | O | 0-3.3V | Transmit |
| 3 | UART-RX | I | 0-3.3V | Receive |
| 4, 12 | NC | No Connection | ||
| 5 | HST_TXD | O | 0-3.3V | Transmit data pin (for upgrading program) |
| 6 | HST_RXD | I | 0-3.3V | Receive data pin (for upgrading program) |
| 7 | ANT | Connect 50 ohm antenna | ||
| 8, 9, 10 | GND | Ground | ||
| 11 | VCC | - | 0-5V | External and Positive supply 3.3-5V |
| 13 | CS | I | 0-5V | High level for normal working, leave open or pull low to enter sleeping mode |
| 14 | PTT | I | 0-3.3V | Module Input, Transmitting/receiving control, pull low to force the module to enter TX state; pull high for Rx state |
| 15 | +3.3V | - | 3.3V output, connect to 50mA | |
| 16 | LINE_OUT | O | Audio output | |
| 17 | T/R | O | 0-3.3V | Module Output, status of Transmitting/receiving, High for TX and Low for Rx |
| 18 | SPKEN | O | Audio amplifier control | |
| 19, 20 | GND | Ground |
6. Application Circuit Diagrams
These diagrams illustrate the internal block structure and typical application circuits for integrating the DMR818S module into a system.
7. Mechanical Dimensions
The following diagram provides the mechanical dimensions of the DMR818S module for integration planning.
8. Accessories
An antenna is a critical component for the communication system, directly impacting overall performance. The DMR818S module requires an antenna with an impedance of 50 Ohm. Common antenna types include rubber straight antennas, sucker antennas, and telescopic antennas. Users should select an antenna appropriate for their specific application environment. For optimal performance, it is recommended to use antennas designed for compatibility with this module.
9. Setup Instructions
To set up the DMR818S module, follow these general guidelines:
- Power Supply: Connect an external positive power supply (3.3V to 5V) to the VCC pin (Pin 11) and ensure all GND pins (8, 9, 10, 19, 20) are properly grounded.
- Antenna Connection: Connect a 50 Ohm antenna to the ANT pin (Pin 7). Ensure the connection is secure and correct for optimal signal transmission and reception.
- Audio Output: For audio output, connect the LINE_OUT pin (Pin 16) to an external audio amplifier and speaker. The SPKEN pin (Pin 18) can be used to control the audio amplifier.
- Audio Input: Connect a microphone or line-in audio source to the MIC_IN pin (Pin 1).
- UART Communication: Use UART-TX (Pin 2) and UART-RX (Pin 3) for serial communication with a microcontroller (MCU) to configure parameters and send/receive data.
- Module Control:
- The CS pin (Pin 13) should be held high for normal operation. Pulling it low will put the module into sleep mode.
- The PTT pin (Pin 14) controls transmit/receive. Pull it low to enter transmit (TX) state and high to enter receive (RX) state.
- Program Upgrading: HST_TXD (Pin 5) and HST_RXD (Pin 6) are used for program upgrading.
10. Operating Instructions
The DMR818S module supports both Digital Mobile Radio (DMR) and Analog modes.
10.1. DMR Mode
- Voice and Text Communication: Supports message transmission and reception with enhanced encryption.
- Call Types: Facilitates various voice call types including All Call, Group Call, and Private Call.
- Call Management: Provides reminders for incoming calls and allows checking of calling status.
- Emergency Features: Includes emergency alarm and radio monitor functionalities.
- Repeater Functionality: Supports repeater operations.
10.2. Analog Mode
- CTCSS/CDCSS: Configurable Continuous Tone-Coded Squelch System (CTCSS) and Continuous Digital-Coded Squelch System (CDCSS).
- Squelch Levels: Adjustable squelch levels to filter out weak signals or noise.
All operating parameters for both modes can be modified and controlled via the module's communication protocol through the UART interface.
11. Troubleshooting
11.1. Module Cannot Communicate Properly
- Verify that the band, channel, data rate, and NET ID are set to the same values on all communicating modules.
- Check for any errors in the power supply connection.
- Ensure the module is enabled (CS pin is high).
- Confirm that the antenna connection is correct and secure.
- Inspect the module for any physical damage.
11.2. Transmission Distance is Shorter Than Expected
- Check if the power supply ripple is excessively large.
- Ensure the antenna type matches the module's requirements and is properly installed.
- Assess the surrounding environment for strong interference sources.
- Identify if there is co-channel interference from other devices.
11.3. Incorrect Data Reception
- Review parameter settings for any improper configurations.
- Check the module's data interface for any faults or poor connections.
12. User Tips
- Antenna Matching: Always use a 50 Ohm impedance antenna for optimal performance and range.
- Frequency Selection: If you require VHF (134-174MHz) or 320-390MHz frequency bands, ensure you specify this requirement when acquiring the module, as different versions may be available.
- Parameter Configuration: A USB bridge board can be very useful for configuring module parameters and conducting basic communication tests with a PC.
13. Warranty and Support
13.1. Warranty
The DMR818S module undergoes 100% testing to ensure a defective rate lower than 0.05%. Free technical support is provided for product-related inquiries.
13.2. After-Sale Service
- Replacements will be provided for quality issues identified in future orders.
- Assistance in evaluating customs risks and selecting appropriate shipping methods.
- Order status tracking until goods reach the client.
- Please note that the G-NiceRF warranty does not apply to products purchased through third-party vendors.
13.3. Contact Support
For any questions or technical assistance, please contact customer support.