Marius Lubbe ZS1ML

I have been using the Retevis RT3S radio ( for a while now and I am very happy with it. It is a dual band DMR radio that can operate on the 136-174 MHz and 400-480 MHz frequency bands. DMR stands for Digital Mobile Radio, a digital standard that allows for clear and secure communication between compatible radios and repeaters. The RT3S supports both analog and digital modes, making it easy to migrate from traditional analog radios to digital technology.

The RT3S has a large color LCD display that shows various information such as channel name, frequency, battery level, signal strength, and mode. It also has a keypad that allows for direct frequency entry and text messaging. It has a programmable side button that can be assigned to different functions such as scan, monitor, or emergency alarm. It has a 2000 mAh battery that provides long-lasting power for the radio.

The RT3S can store up to 3000 channels, 10000 contacts, and 250 zones in its memory. A channel is a combination of frequency, mode, and other settings that can be used for communication. A contact is a name or ID of another radio user that can be called individually or as part of a group. A zone is a group of channels that can be easily accessed by rotating the knob on the top of the radio.

The RT3S supports DMR Tier I and II standards, which means it can communicate with other DMR radios that use the same standards and encryption. Tier I is for license-free use on the same frequency, while Tier II is for licensed use on different frequencies with repeaters. The RT3S also supports TDMA (Time Division Multiple Access) and dual time slot technologies, which allow for two simultaneous conversations on the same frequency.

The RT3S has an optional GPS module that can send and receive location information to other radios or online services. The GPS function can also be used for APRS (Automatic Packet Reporting System), which is a system that broadcasts location and status information over radio waves. The RT3S can also be used as a hotspot device that connects to the internet via a PC and allows for communication with other radios or online platforms such as BrandMeister or DMR Plus.

GD77 in white on black mode

I decided to try the Open GD77 firmware on my RT3S radio after hearing about its features and enhancements from other users. The Open GD77 firmware is an open-source project that aims to improve the functionality and usability of the Retevis RT3S radio. It is based on the original firmware of the Radioddity GD-77 radio, which has a similar hardware to the RT3S. The Open GD77 firmware adds many features and enhancements to the radio, such as:

    • A more user-friendly interface with customizable menus and colors

    • A better scanning performance with faster scan speed and priority scan

    • A more flexible channel selection with VFO mode and direct frequency entry

    • A more reliable DMR operation with improved audio quality and error correction

    • A more versatile codeplug management with support for multiple codeplugs and import/export functions

    • A more advanced hotspot mode with support for MMDVM protocol and multiple modes (DMR, D-Star, YSF, etc.)

    • A more accessible firmware update process with a dedicated CPS software and USB cable

The Open GD77 firmware is still in development and may have some bugs or limitations. It is not officially supported by Retevis or TYT, the manufacturers of the RT3S radio. Installing the Open GD77 firmware may void the warranty of the radio and may cause some issues with the calibration data or the official firmware. Therefore, I installed the Open GD77 firmware at my own risk and followed the installation instructions carefully.

Installation instructions

Disclaimer: The installation instructions provided here are just a rough guide and are not intended to replace the official instructions from the Open GD77 website. I followed the official instructions from here to install the Open GD77 firmware on my radio. I take no responsibility if you break your radio during this firmware upgrade.

To install the Open GD77 firmware on my Retevis RT3S radio, I needed to have:

    • A working copy of the official firmware that matches my radio model and version

    • The official firmware loader or update driver installed on my PC

    • The latest version of the Open GD77 CPS software downloaded from here

    • The latest version of the Open GD77 Alpha firmware downloaded from here

    • The official MD9600 V5 firmware downloaded from here (used as a donor firmware)

    • A USB cable to connect my radio to my PC

The installation steps were as follows:

    1. I backed up the calibration data and codeplug of my radio using the official CPS software. To access the calibration data, I held Control + T until the test screen was displayed.

    1. I ran the Open GD77 CPS software and selected Tools -> Flash Manager -> Download from radio.

    1. I selected “Use external donor file” and browsed to the MD9600 V5 firmware file.

    1. I selected “Use external SGL file” and browsed to the Open GD77 Alpha firmware file.

    1. I clicked OK and waited for the flashing process to complete.

    1. I disconnected and reconnected the USB cable to reset my radio.

    1. I ran the Open GD77 CPS software again and selected Tools -> Flash Manager -> Upload to radio.

    1. I selected “Restore calibration data” and browsed to the backup file created in step 1.

    1. I clicked OK and waited for the uploading process to complete.

    1. I disconnected and reconnected the USB cable to reset my radio.

The installation was now complete. I could now use the Open GD77 CPS software to create or edit codeplugs for my radio. Note that original CPS software was incompatible with Open GD77 Firmware so I had to use GD77 CPS to create new codeplug from scratch.

RT3S with Open GD77 on left and original Retevis firmware look on right. I prefer the clean look of Black on White theme in GD77.


I have been using my Retevis RT3S radio with Open GD77 Firmware for some time now and I am very impressed with it. It is a great improvement over original Firmware in terms of performance functionality. It has many features that are not available in original Firmware such as hotspot mode VFO mode priority scan multiple codeplugs etc. It also has more user-friendly interface with customizable menus colors.

However, installing Open GD77 Firmware was not without risks as it may cause some compatibility issues damage to my radio. I had follow installation instructions carefully be aware its limitations. For example, only some models RT3S have GPS module so I had check my radio model before using installing any GPS-related functions features.

Overall, I am very happy with my Retevis RT3S radio with Open GD77 Firmware would recommend it anyone who wants reliable affordable dual band DMR radio enhanced features. The functionality and look of GD77 is under constant development and we hope to see some more features from this community based open software.

Feature comparison

The following table shows some of main differences between my experience original Firmware vs Open GD77 Firmware Retevis RT3S Radio

Feature Original Firmware Open GD77 Firmware
Interface Fixed menu layout limited customization options Flexible menu layout various customization options
Scan Slow scan speed no priority scan option Fast scan speed priority scan option
Channel selection Channel mode only no direct frequency entry Channel mode VFO mode direct frequency entry
DMR operation Standard audio quality error correction Enhanced audio quality error correction
Codeplug management Single codeplug support no import/export functions Multiple codeplug support import/export functions
Hotspot mode No hotspot mode support Hotspot mode support MMDVM protocol multiple modes
Firmware update Requires official firmware loader update driver Requires dedicated CPS software USB cable

Leave a Comment

Your email address will not be published. Required fields are marked *

Translate »
Scroll to Top