ELRS-915M-TX High-Frequency Head Fast Frequency Locking

Core Positioning
A high-frequency head with rapid frequency locking capability, optimized for signal acquisition and synchronization mechanisms to significantly enhance system response speed and dynamic adaptability. It serves as a professional RF front-end solution tailored for high-mobility, frequency-hopping communication, and fast-switching scenarios.

Application Scenarios

1. Frequency-Hopping Communication Systems: Suitable for military, governmental, and other secure communication devices requiring anti-interference and low probability of interception.

2. High-Speed Mobile Platforms: Airborne or vehicular communication equipment requiring frequent channel switching or rapid signal reacquisition during high-speed movement.

3. Dynamic Spectrum Access Systems: Intelligent communication devices such as cognitive radios that need to quickly scan and lock onto available frequency bands.

4. Test and Measurement Instruments: Spectrum analyzers, signal generators, and other instruments requiring fast frequency locking and tracking of measured signals.

Core Selling Points

1. Millisecond-Level Rapid Frequency Locking: Utilizes high-speed phase-locked loops and intelligent algorithms to drastically reduce the time from frequency switching to stable locking, enhancing system real-time performance.

2. High Dynamic Adaptability: Achieves reliable and fast frequency tracking and locking even in scenarios with rapidly changing signal strength, frequency offset, or Doppler effects.

3. Enhanced Overall System Performance: Reduces communication link establishment time and switching delays, improving communication continuity and reliability in complex electromagnetic environments.

Intelligent Frequency Management: Collaborates with upper-layer protocols to enable rapid channel scanning, automatic frequency point switching, and adaptive tuning, optimizing spectrum utilization efficiency.

Essential Parameter

Frequency bands:

915MHz (FCC) and 868MHz (EU)

output power:

0.5W/1W/2W/5W/10W (Default factory setting: 5W)

Refresh rate:

25Hz/50Hz/100Hz/200Hz

Power consumption:

8.4V,2.3A@10W,200Hz, 1:200

Antenna connector:

SMA

USB port:

Type-C

Battery input voltage range:

5-8.4V (2S)

Built-in fan power supply:

5V

alloy heat dissipation fin, alloy cover

Main control IC:

ESP32+LR1121, with ESP8285 as the back-up chip

Warning: Do not connect a power supply of 2S or higher than 8.4V to the ELRS-915M-TX high frequency head. Otherwise, it may cause permanent damage.

Warning: Before powering on the ELRS-915M-TX high-frequency head, install the manufacturer's matching antenna. Failure to do so may damage the PA chip and reduce power output.

The ELRS-915M-TX high-frequency head features a set of relay-compatible interfaces for user selection, with its base compatible with all Micro (also known as JR or SLIM) remote controls available on the market. The interface and design are shown in the figure below.

Appearance and Heat Dissipation Structure

Within the compact JR interface standard dimensions, the system integrates up to 10W of transmission power. To achieve stable performance at this extreme level, the design team redefined the high-frequency head's structural design. By combining an aluminum alloy fin heat sink, an efficient turbo fan, a metal casing, and a 10W RF PA chip with dedicated heat dissipation alloy, they created a product that integrates efficient heat dissipation, robust protection, and strong anti-interference capabilities. This ensures reliable performance for ultra-long-range navigation in harsh environments.

Pre-Frequency Basic Configuration

The ELRS-915M-TX high-frequency head is designed to receive only Crossfire Serial Data Protocol (CRSF) signals by default. The remote control's high-frequency interface must support CRSF signal output. Using the OpenTX remote control system as an example, this guide demonstrates how to configure the remote to output CRSF signals and control the ELRS high-frequency head with a LUA script.

3.1 CRSF Protocol

In the OpenTX system, select MODELSELECTION to access the MODELSETUP interface. Here, disable Internal RF (set to OFF), enable External RF, and set the output mode to CRSF, as shown in the figure below.

Connect the ELRS-915M-TX high-frequency head correctly and configure the remote control as the CRSF output for the External RF head as described above.

3.2 LUA Script Installation and Control (already Available)

To adjust the power, refresh rate, and frequency of the ELRS high-frequency head, you need to use the OpenTX system's LUA script, as shown below.

1. Copy the official LUA script ELRS.lua to the remote control's SD card, located in the Scripts/Tools folder.
2. On the OpenTX system, press and hold either the SYS button (as found on RadioMaster T8 remote controls) or the MENU button (as used in Frsky Taranis devices).
3. Using the X9D remote control or similar devices, access the SD-HC CARD interface. In this interface, select the ELRS.lua script and execute it.
4. If the LUA script runs successfully, the interface will appear as shown below. (Default factory setting: 5W)

• Using LUA scripts, you can configure parameters such as Rate (refresh rate), Ratio (feedback packet rate), and Power (output power). All LUA script functions are detailed in Table 1 below.

Table 1 Script Description Table

Note: The official LUA script ELRS.lua can be downloaded from the ELRS support website (URLs are provided in the information section).

4. Frequency Discrimination Method

The ELRS high-frequency head uses the ExpressLRSV3.5.0 official protocol in its factory firmware and has no binding phrase configured. Therefore, the receiving end must also be V3.0.0 to V3.5.0 and has no binding phrase set.

The frequency steps are as follows

1. Step1: After the receiver is powered on, press the receiver button for a long time. The LED on the receiver will enter the double flash state, indicating that the receiver has entered the frequency matching mode
2. Step2: Install the antenna on the high-frequency head, insert the remote control, and insert the external XT30 port battery (optional). Enter the Express LRS configuration interface, scroll down to find the Bind option, as shown in the figure below.

3. Step3: After pressing the Bind button, the receiver enters a slow flash state and then a normal light state for about 2 seconds, indicating that the frequency reception is successful

5. Power Settings

The ELRS high-frequency head supports power outputs of 0.5W,1W,2W,5W, and 10W.

The ELRS high-frequency hair transmitter power switching uses a LUA script. Select Power to switch directly between 0.5W,1W,2W,5W, and 10W. For details, see "LUA Script Control".

Company Information

Shenzhen Fengqing Instrument Co., Ltd.

Crafted in China, Quality Forges Low-Altitude Security.
Upholding a "customer-first" philosophy, Fengqing Instrument is committed to providing professional service throughout the entire product lifecycle:

• Pre-sales Consultation: Customized solution designs and product recommendations based on client needs.
• In-sales Support: Comprehensive technical support for installation, debugging, and operational training.
• After-sales Service: Rapid-response system including remote support and on-site maintenance.