The **FM-RTFQ1** is a compact, high-performance FM transmitter module designed for telemetry and wireless data transfer. It operates in the 433MHz frequency band (ISM) and is typically paired with the **FM-RRFQ1** receiver. --- ## 1. Technical Specifications Below are the primary electrical characteristics of the FM-RTFQ1 module: | Parameter | Specification | | :--- | :--- | | **Operating Voltage** | 2.0V to 15V DC | | **Operating Frequency** | 433.92 MHz | | **Modulation Type** | FSK (Frequency Shift Keying) | | **Output Power** | +5dBm (approx. 3mW) | | **Data Rate** | Up to 9.6 Kbps | | **Interface** | TTL / CMOS Compatible | | **Operating Temp** | -25°C to +80°C | --- ## 2. Key Internal Components & Architecture The module is built using **Surface Mount Technology (SMT)** on a ceramic substrate, which ensures high stability and low frequency drift. ### A. Frequency Synthesis * **SAW Resonator:** It utilizes a Surface Acoustic Wave (SAW) resonator to lock the frequency. This makes it much more stable than LC-based transmitters, preventing frequency shifts due to temperature or handling. * **Crystal-less Design:** Because it uses a SAW filter, it achieves a small footprint while maintaining high spectral purity. ### B. Modulation Circuitry * **FSK Modulator:** Unlike cheaper ASK (Amplitude Shift Keying) modules, the FM-RTFQ1 uses Frequency Shift Keying. This makes the signal significantly more resistant to electrical noise (EMI) and atmospheric interference. * **Buffer Stage:** An internal buffer decouples the oscillator from the antenna, ensuring that the frequency remains stable even if the antenna is touched or moved. --- ## 3. Pin Configuration The module typically features a 4-pin or SIL (Single In-Line) package: | Pin Number | Name | Description | | :--- | :--- | :--- | | 1 | **ANT** | External Antenna connection (approx. 15.5cm wire) | | 2 | **GND** | Common Ground | | 3 | **Data In** | Digital input from Microcontroller (TTL level) | | 4 | **VCC** | Positive Supply Voltage | --- ## 4. Design Considerations When integrating the FM-RTFQ1 into an electronic circuit, keep the following in mind: 1. **Supply Decoupling:** Use a 100nF ceramic capacitor close to the VCC/GND pins to filter out noise from the power supply. 2. **Antenna:** A simple 1/4 wave whip antenna (solid copper wire) is usually sufficient. Avoid routing the antenna near high-speed digital lines. 3. **Data Encoding:** While the module can handle raw serial data, it is best used with an encoder (like the **HT12E**) or a microcontroller running Manchester encoding to ensure DC balance in the FSK signal. ---