Hertzian
Hertzian

Noise Floor ChallengeEar Training

Decode Morse code messages hidden in static. As the Signal-to-Noise Ratio drops, you'll discover why digital modes and coding gain are essential for weak-signal communication.

The Noise Floor Challenge

Decode Morse code messages hidden in increasing noise. As the Signal-to-Noise Ratio drops, you'll need sharper ears — and the FFT display to help when your ears give up.

Level 1
Crystal Clear
SNR: +20 dB
Level 2
Some Static
SNR: +10 dB
Level 3
Noisy Channel
SNR: +3 dB
Level 4
At the Floor
SNR: 0 dB
Level 5
Below the Floor
SNR: -3 dB
Level 6
Deep Space
SNR: -10 dB

Understanding the Noise Floor

  • 📊What is SNR?

    Signal-to-Noise Ratio measures how much stronger a signal is compared to background noise, expressed in decibels (dB). At +20 dB the signal has 100x the power of the noise; at 0 dB they're equal; at -10 dB the noise has 10x the power.

  • 📡The Noise Floor

    Every receiver has a minimum detectable signal level — the noise floor. It's determined by thermal noise, component quality, and bandwidth. Thermal noise is -174 dBm/Hz + 10·log10(bandwidth), so a 10x narrower filter lowers the floor by 10 dB, while a receiver's noise figure raises it dB for dB.

  • 🛰️Why Digital Modes Work

    Modes like FT8 and WSPR can decode signals down to about -21 dB and -31 dB SNR (measured in a 2.5 kHz bandwidth) — signals completely buried in noise. They use forward error correction and long integration times. NASA's Voyager 1 signal arrives at Earth near -150 dBm and is recovered using the same principles.