Introduction to RSSI and LQ in ExpressLRS
If you're into RC flying or DIY radio control projects, you've probably come across the terms RSSI and LQ, especially when working with ExpressLRS. But what do these signals really mean, and how do they affect your flying experience? This guide will break down what RSSI (Received Signal Strength Indicator) and LQ (Link Quality) are, how ExpressLRS uses them, and why understanding them helps you fly better.
What is RSSI?
RSSI stands for Received Signal Strength Indicator. Simply put, it tells you how strong the radio signal is that your receiver is picking up from your transmitter. The higher the RSSI value, the stronger the signal.
In ExpressLRS, RSSI is measured by the receiver and sent back to your transmitter or flight controller. This helps you know how good your connection is in real-time.
How ExpressLRS Measures RSSI
ExpressLRS uses the radio hardware's built-in capabilities to measure the power of incoming signals. This is usually expressed in dBm (decibels relative to a milliwatt), but ExpressLRS normalises this into a percentage or a simple numerical scale for easier interpretation.
What is Link Quality (LQ)?
Link Quality, or LQ, gives a broader picture than RSSI. While RSSI only tells you how strong the signal is, LQ tells you how good the connection actually is. This includes how many packets are successfully received and how reliable the data link is.
ExpressLRS calculates LQ based on error rates, packet loss, and signal strength. It's often displayed as a percentage, where 100% means a perfect link, and lower values indicate potential issues.
Why LQ Matters More Than RSSI Alone
Imagine you have a strong signal (high RSSI) but lots of interference causing data errors. Your LQ would be low because the link isn't reliable. Conversely, you might have a moderate signal but excellent data integrity, resulting in a high LQ.
How RSSI and LQ Work Together in ExpressLRS
ExpressLRS constantly monitors both RSSI and LQ to maintain a stable connection. Here’s what happens behind the scenes:
- RSSI helps detect signal strength: Useful for understanding how far or obstructed your model is from the transmitter.
- LQ tracks data reliability: Ensures commands and telemetry are transmitted without errors.
- Adaptive transmission: ExpressLRS can adjust parameters like power and data rate based on RSSI and LQ to optimise range and performance.
Practical Tips for UK RC Pilots
Understanding RSSI and LQ can improve your flying and tinkering experience:
- Keep an eye on LQ: It’s a better indicator of link health than RSSI alone.
- Use telemetry displays: Many OSDs and radios show RSSI and LQ values to help you make informed decisions in-flight.
- Adjust antennas and placement: Poor antenna orientation can lower both RSSI and LQ.
- Test in different environments: Urban areas may have more interference affecting LQ despite good RSSI.
Conclusion
RSSI and LQ are essential tools in your ExpressLRS setup. RSSI tells you how strong the signal is, while LQ tells you how good the connection really is. By monitoring both, you can better understand your radio link’s health, avoid surprises in flight, and make smarter DIY tweaks to your gear.
Happy flying and tinkering!
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