RA-02 SX1278 LoRa Module
Budget SX1278-based LoRa module for 433MHz long-range links.
The RA-02 is a budget LoRa transceiver module built around Semtech's SX1278 chip, offering long-range, low-power wireless communication on the 433MHz band. LoRa's chirp spread-spectrum modulation trades data rate for range and noise immunity, letting the RA-02 reach several kilometers line-of-sight at very low transmit power — making it a favorite for remote telemetry, weather stations, and long-range sensor links where Wi-Fi and Bluetooth simply can't reach.
Specifications
| Chipset | Semtech SX1278 LoRa transceiver |
| Frequency band | 433MHz (other SX127x-based modules cover 868MHz/915MHz) |
| Operating voltage | 1.8V–3.7V DC (3.3V typical — NOT 5V tolerant) |
| Operating current | ~10.8 mA RX, up to ~120 mA TX at max power |
| Transmit power | Up to +20 dBm (100mW), configurable in software |
| Range | Several kilometers line-of-sight typical, dependent on antenna, terrain, and spreading factor settings |
| Modulation | LoRa chirp spread spectrum, also supports legacy FSK/OOK modes |
| Interface | SPI, plus DIO interrupt pins for packet-ready/done signaling |
Pinout
| Pin | Name | Description |
|---|---|---|
| 1 | 3.3V | Power, 3.3V DC only |
| 2 | GND | Ground |
| 3 | MOSI | SPI data in |
| 4 | MISO | SPI data out |
| 5 | SCK | SPI clock |
| 6 | NSS (CS) | SPI chip select, active LOW |
| 7 | RESET | Active-LOW module reset |
| 8 | DIO0 | Interrupt pin signaling packet transmit-done or receive-ready, used by most LoRa libraries |
| 9 | ANT | Antenna connection — a matching 433MHz wire or spring antenna is required for usable range |
The RA-02 communicates over SPI, not UART, so it needs 4 SPI lines plus RESET and DIO0 wired to the host microcontroller (libraries like Sandeep Mistry's LoRa library or RadioHead expect this exact pin set). Like most bare radio modules, all logic is 3.3V only — use a level shifter when wiring to 5V boards like the Arduino Uno, and always attach an antenna before powering on transmit to avoid damaging the power amplifier.
Variants
Always match the module's frequency variant to your region's legal ISM band — 433MHz is common in Asia and parts of Europe, while 868MHz (EU) and 915MHz (US/Australia) are used elsewhere; using the wrong band can violate local radio regulations. For fast prototyping without separate microcontroller wiring, an all-in-one board like the Heltec LoRa32 is far more convenient than wiring a bare RA-02.
| Variant | Price |
|---|---|
| RA-02 (433MHz, SX1278) | ~$2-4 |
| RA-01/RA-02 with SX1276/RFM95 (868/915MHz) | ~$3-6 |
| LoRa module + built-in microcontroller (e.g. Heltec/TTGO LoRa32) | ~$10-20 |