SDRGEEK MMDVM Duplex Hotspot Board

1. Introduction

This manual provides detailed instructions for the setup, operation, and maintenance of your SDRGEEK MMDVM Duplex Hotspot Board. This device is a multi-mode digital voice modem designed to support various digital radio protocols, including D-STAR, P25, DMR, and YSF, enabling communication between different digital two-way radio modes. It is compatible with Raspberry Pi 3 and Raspberry Pi Zero W.

Please read this manual thoroughly before using the product to ensure proper functionality and to maximize your experience.

2. Product Overview

The MMDVM Duplex Hotspot Board is a fully assembled device featuring a high-performance 32-bit ARM processor and two ADF7021 chips for duplex operation. It includes an 0.96-inch OLED display and comes pre-mounted in a metal housing.

2.1 Package Contents

• MMDVM Duplex Hotspot Board (with Raspberry Pi Zero W, OLED display, and metal housing)
• 8G TF Card (pre-configured with Pi-Star settings)
• UHF Antennas (x2)

2.2 Device Features

• Duplex Operation: Supports two time slots on DMR.
• Multi-Mode Support: Compatible with D-STAR, P25, DMR, YSF, and NXDN.
• Frequency Range: UHF 433-900MHz, VHF 144-220 MHz (in single mode).
• RF Power: Up to 10mW.
• Display: Integrated 0.96-inch OLED for status information.
• Connectivity: HDMI, OTG, DC5V (Micro USB for power).
• Status Indicators: Onboard LEDs for Tx, Rx, PTT, and Mode status.

Figure 1: SDRGEEK MMDVM Duplex Hotspot Board. This image shows the compact device with two antennas, an OLED display, and visible ports.

Figure 2: Top view of the hotspot, highlighting the HDMI, Otg (USB On-The-Go), and DC5V power input ports. The Wi-Fi symbol indicates wireless capability.

Figure 3: Detailed view of the device's display screen, antenna connectors, and charging indicator LEDs, providing visual feedback on the device's status.

3. Setup Instructions

Before initial use, it is necessary to perform some basic setup steps. The included 8G TF card comes with a pre-configured Pi-Star image, simplifying the initial configuration process.

3.1 Hardware Connection

1. Insert TF Card: Ensure the pre-configured 8G TF card is securely inserted into the TF card slot on the hotspot board.
2. Attach Antennas: Screw the two UHF antennas onto the antenna connectors. Ensure they are finger-tight. The upper connector is for TX, and the lower is for RX.
3. Power On: Connect the device to a power source using a mobile charger or a USB cable connected to a computer/laptop via the DC5V Micro USB port. The device will power on automatically.

Figure 4: The hotspot board connected to a portable power bank, demonstrating its mobile power capability.

3.2 Initial Pi-Star Configuration (First-Time Use)

The Pi-Star software allows for comprehensive configuration of your hotspot. For first-time setup, you will need to connect to its default Wi-Fi network.

1. Connect to Pi-Star Wi-Fi: On your computer or mobile device, search for Wi-Fi networks. Connect to the network named pi-star. The default password is raspberry. Note that the Raspberry Pi Zero W only supports 2.4GHz Wi-Fi.
2. Access Pi-Star Dashboard: Open a web browser and navigate to http://pi-star/ or http://192.168.50.1/. The default username is pi-star and the password is raspberry.
3. Configure Wi-Fi (Optional): To connect the hotspot to your home Wi-Fi network, navigate to the 'Configuration' section. Select 'Wireless Configuration' and enter your home Wi-Fi SSID and password. Save and connect. The hotspot will reboot and attempt to connect to your specified network.
4. Modem Selection: In the Pi-Star configuration, ensure the modem type is set to STM32_HS_GPIO.
5. Frequency Settings: Set your desired TX and RX frequencies. For duplex operation, it is recommended that the TX and RX frequencies are 10MHz or more apart. For example, 433.550000MHz for DMR.
6. DMR Configuration: If using DMR, configure your DMR ID and talkgroups in the appropriate sections of the Pi-Star dashboard.

Important Note: You must complete the initial setup before using the hotspot for digital radio communication. Refer to the Pi-Star documentation for advanced configurations.

4. Operating Instructions

Once configured, your MMDVM Duplex Hotspot Board is ready for operation across various digital modes.

4.1 Supported Modes

The hotspot supports the following digital radio modes:

• D-STAR
• P25
• DMR (Digital Mobile Radio)
• YSF (Yaesu System Fusion)
• NXDN

4.2 Duplex Operation

The duplex design allows for simultaneous transmission and reception on two different time slots (Slot 1 and Slot 2) in DMR mode, enhancing efficiency and capacity.

4.3 Status Indicators

The onboard LEDs provide visual feedback on the hotspot's operational status:

• Tx: Indicates transmission activity.
• Rx: Indicates reception activity.
• PTT: Indicates Push-To-Talk status.
• Mode: Indicates the current operating mode.

5. Maintenance

To ensure the longevity and optimal performance of your MMDVM Duplex Hotspot Board, follow these maintenance guidelines:

• Keep Clean: Regularly clean the exterior of the device with a soft, dry cloth. Avoid using liquid cleaners or solvents.
• Environmental Conditions: Operate the device in a cool, dry environment, away from direct sunlight, excessive heat, and moisture.
• Software Updates: Periodically check for updates to the Pi-Star software to benefit from new features, bug fixes, and improved performance. Instructions for updating Pi-Star are available on the official Pi-Star website.
• TF Card Care: Handle the TF card with care. Avoid frequent removal or insertion to prevent damage. Ensure proper shutdown procedures are followed before removing power to prevent data corruption on the TF card.

6. Troubleshooting

If you encounter issues with your MMDVM Duplex Hotspot Board, refer to the following common troubleshooting steps:

• Device Not Powering On: Ensure the power cable is securely connected to the DC5V port and the power source is active. Try a different USB cable or power adapter.
• OLED Display Not Working: If the OLED display does not show information, ensure the device is powered on and the TF card is properly inserted. A complete reboot may resolve the issue.
• Cannot Connect to Pi-Star Wi-Fi: Verify that the hotspot is powered on. Ensure your connecting device (computer/phone) is within range and supports 2.4GHz Wi-Fi. Double-check the Wi-Fi SSID (pi-star) and password (raspberry).
• Access Denied to Pi-Star Dashboard: Confirm you are using the correct default username (pi-star) and password (raspberry). If you have changed them, use your updated credentials. Clear your browser cache or try a different browser.
• No Digital Voice Communication:
  • Verify that the modem type is correctly set to STM32_HS_GPIO in the Pi-Star configuration.
  • Check your TX and RX frequency settings. Ensure they are valid and sufficiently separated for duplex operation.
  • Confirm your DMR ID and talkgroup configurations are correct.
  • Ensure your radio is properly configured to communicate with the hotspot.
• Slow Performance: While the Raspberry Pi Zero W is capable, some operations might feel slower compared to more powerful Raspberry Pi models. This is generally expected.
• Antenna Issues: Ensure both antennas are securely connected. For optimal performance, ensure the TX and RX frequencies are appropriately separated.

Note: A basic understanding of digital radio protocols (DMR, D-STAR, etc.) is beneficial for effective configuration and use of this hotspot.

7. Specifications

8. Warranty and Support

SDRGEEK is committed to providing high-quality electronic products and comprehensive customer support.

8.1 After-Sales Support

The product includes up to one year of after-sales support. This covers assistance with product installation, usage guidance, and troubleshooting. Solutions will be provided for any issues encountered.

8.2 Contact Information

For professional pre-sale consultation or high-quality after-sales service, please visit the official SDRGEEK store on Amazon or contact customer support through the platform where you purchased the product.

You can visit the SDRGEEK store here: SDRGEEK Amazon Store