Dynamic notch filters have become essential for clean flight because they eliminate motor noise that changes with throttle position. Unlike static notch filters that target fixed frequencies, dynamic filters move with your motors' actual resonant peaks as RPM changes during flight.
Start by connecting your flight controller to Betaflight or your specific configurator. Navigate to the PID Tuning tab and look for the filtering section. Most controllers running Betaflight 4.3 or newer come with dynamic notch filters enabled out of the box, typically set to track between 5 and 8 peaks simultaneously.
The key parameters you'll adjust are filter count, frequency range, and Q factor. For a typical 5-inch freestyle quad, I recommend starting with these values: set dynamic notch count to 5, minimum frequency to 100Hz, and maximum frequency to 600Hz. The Q factor, which controls how narrow each notch is, works well at 120 for most builds. Heavier quads or those with softer frames might need the minimum frequency dropped to 80Hz because they resonate lower.
Your gyro sample rate matters significantly here. Running at 8kHz gyro and 4kHz PID loop gives the filters enough resolution to track peaks accurately. If you're on older hardware limited to 4kHz gyro, reduce your notch count to 3 or 4 to avoid overloading the processor.
After initial setup, fly your quad and pull the blackbox log. Import it into Blackbox Explorer and examine the gyro noise spectrum. You'll see clear spikes where motor noise exists. The dynamic notch filters should be sitting right on top of these peaks. If you see unfiltered noise spikes, increase your notch count by one or two. If the filters seem to be chasing ghost peaks or creating excessive delay, reduce the count.
Temperature affects motor harmonics too. I've noticed that motors generate different resonant frequencies when cold versus after several packs. The dynamic filters adapt to this naturally, which is why they outperform static filters dramatically.
For racing quads where latency matters more than absolute noise suppression, consider reducing the notch count to 3 and increasing the minimum frequency to 150Hz. This keeps filtering light while protecting against the most harmful resonances. Freestyle builds benefit from more aggressive filtering with 5 to 7 notches since smoothness matters more than millisecond response times.
