The **ST-RX04-ASK** is a low-cost, high-performance superheterodyne wireless receiver module designed for remote control systems. It operates using **ASK (Amplitude Shift Keying)** or **OOK (On-Off Keying)** modulation. --- ## 1. Technical Specifications The following table highlights the primary electronic characteristics of the module: | Parameter | Specification | | :--- | :--- | | **Operating Voltage** | 3.3V to 5.5V DC | | **Operating Current** | ~3.8mA to 5mA | | **Frequency Range** | 315MHz or 433.92MHz (Common variants) | | **Receiver Sensitivity** | -108 dBm to -110 dBm | | **Data Rate** | up to 10 Kbps | | **Modulation Type** | ASK / OOK | | **Operating Temp** | -30°C to +85°C | --- ## 2. Key Components & Architecture The ST-RX04-ASK typically utilizes a **Superheterodyne architecture**, which is superior to older Super-regenerative designs in terms of stability and interference rejection. ### Main Integrated Circuit (IC) * **SYN470R / SYN480R (or similar):** Most of these modules are based on a CMOS monolithic receiver chip. This IC handles the RF-to-baseband conversion, signal filtering, and data slicing. * **Crystal Oscillator:** Provides a stable reference frequency, ensuring the receiver does not "drift" due to temperature changes. ### Pinout Configuration The module usually features a 4-pin or 5-pin interface: 1. **VCC:** Power input (Positive). 2. **DATA:** Digital output (connects to MCU like Arduino/STM32). 3. **DATA (Duplicate):** Often two pins are provided for data for layout flexibility. 4. **GND:** Ground. 5. **ANT:** Solder point for a 1/4 wave wire antenna. --- ## 3. Implementation Logic The module acts as a "bridge" between the wireless RF spectrum and a microcontroller. * **Antenna Stage:** Captures the electromagnetic waves. * **Mixer & Local Oscillator:** Down-converts the high-frequency signal (e.g., 433MHz) to an Intermediate Frequency (IF). * **Data Slicer:** Converts the analog signal into a clean square-wave digital output (Logic 0 or 1). * **MCU Processing:** A microcontroller (using libraries like `RadioHead` or `RCSwitch`) interprets the pulses to decode specific commands or IDs. --- ## 4. Usage Tips * **Antenna Length:** For 433MHz, use a **17.2 cm** straight copper wire. For 315MHz, use a **22.6 cm** wire. * **Noise Management:** Since ASK is sensitive to electrical noise, place a 0.1µF capacitor across VCC and GND to filter power supply ripples. * **Line of Sight:** While it can penetrate walls, range is significantly improved with a clear line of sight.