Instant Spectrum2400 – 2483.5 MHz
Waterfall Spectrogramtime flows downward · newest at top
Shannon Capacity HistoryC = B·log₂(1+SNR)
Per-User Metrics
Background: Frequency-Hopping Spread Spectrum (FHSS) spreads a narrowband signal across many channels by hopping pseudo-randomly among them according to a code shared by transmitter and receiver. Because any single narrowband jammer or interferer can only ever occupy a small fraction of the hopping channels, a hopping user is affected only briefly on each pass through the jammed band, while a non-hopping ("parked") user sitting on a jammed channel suffers continuously. This resilience, combined with the Shannon capacity C = B·log₂(1+SNR) (B = bandwidth, SNR = signal-to-noise ratio) of each hop, is what makes FHSS attractive for interference-rich environments like the unlicensed 2.4 GHz ISM (Industrial, Scientific, and Medical) radio band.
Description of This Web Application: Configure the number of simultaneous users and the hop code length, then press Play to watch a live waterfall spectrogram of the 2.4 GHz band as each user hops between 1 MHz channels. Toggle a narrowband jammer on or off and set its center frequency and bandwidth, and separately toggle FHSS on or off to park every user on a single fixed channel. Per-user SNR, an instantaneous Shannon capacity (computed fresh each observation), and a running average of that rate over past observations are all tracked live. You will directly observe how hopping keeps throughput largely intact even with a jammer present, and how disabling hopping while parked on a jammed channel causes that user's data rate to collapse and stay down.