Spectrum 28 September 2026 · 6 min read
Reading a spectrum waterfall like an engineer
Waterfall plots look intimidating. Learn the four patterns that explain most Wi-Fi interference problems.
A spectrum analyser shows raw RF energy — not just Wi-Fi. The waterfall view plots frequency horizontally, time vertically and signal strength as colour. Once you know a few signatures, it becomes one of the fastest troubleshooting tools you have.
Wi-Fi transmissions
Wi-Fi appears as bursts across a channel width (20, 40, 80 MHz or more). Lots of bursts on one channel means high utilisation — normal at busy times, a problem if it is constant.
Microwave ovens
A microwave oven produces a wide, pulsing block of energy in the upper part of 2.4 GHz, usually for a few minutes at a time around meal breaks. If complaints cluster near a kitchen at lunchtime, this is your suspect.
Continuous transmitters
Video senders, some wireless cameras and old analogue devices show as a constant vertical stripe. They occupy the channel 100% of the time, and no Wi-Fi tuning will fix that — the device has to move channel or be removed.
Frequency hoppers
Bluetooth and some proprietary devices hop across the band, leaving short scattered marks. They rarely cause serious problems unless there are a lot of them in one place.
Duty cycle matters more than signal strength. A weak interferer that is always on can hurt more than a strong one that appears for a second.
From picture to fix
- Correlate captures with when and where users complain
- Identify the interferer and measure its duty cycle
- Change channels, adjust power or remove the source
- Re-capture to prove the fix
