SmartSDR provides several advanced Noise Mitigation Features designed to automatically reduce unwanted noise and interference.
Each filter targets a specific noise type and operates with no user-adjustable parameters — just turn it on when needed.
NRL – Noise Reduction Leaky
Purpose: Reduce random band noise and background hiss.
How It Works: Adaptive time-domain “Leaky LMS” filter that preserves correlated signals (voice, CW) while removing uncorrelated noise.
Best For: Daily operation when signals are buried in static.
Avoid When: Signals are already clean — may introduce slight “watery” audio if unnecessary.
Available On: All SmartSDR radios.
ANFL – Adaptive Notch Filter (Leaky)
Purpose: Remove steady tones or power-line hum.
How It Works: An Adaptive filter that detects and cancels correlated tone interference.
Best For: Hum, steady carriers, or single persistent tones.
Avoid When: No hum/tone is present — could partially notch the desired signal.
Available On: All SmartSDR radios.
ANFT – Adaptive Notch Filter (FFT)
Purpose: Suppress up to five narrowband tones in the passband (≥ –110 dB).
How It Works: FFT-based spectral notch filter that identifies and removes stable tone noise.
Best For: Power supply hum, transformer buzz, grounding-related tones, or spurs.
Available On: All SmartSDR radios.
NRF – Noise Reduction Filter
Purpose: Reduce steady background noise using frequency-domain processing.
How It Works: Spectral subtraction estimates and removes broadband noise from each frequency bin.
Best For: Constant hiss, fan noise, or environmental hum.
Available On: FLEX-8000 and Aurora series.
NRS – Noise Reduction Speech
Purpose: Improve speech clarity by lowering noise most aggressively between words.
How It Works: Spectral subtraction combined with Voice Activity Detection (VAD).
Best For: SSB/AM voice operation in consistent noise environments.
Available On: FLEX-8000 and Aurora series.
RNN – Recurrent Neural Network Suppression
Purpose: AI-based removal of complex or varying noise while keeping speech natural.
How It Works: Deep-learning model that separates speech from noise across time and frequency.
Best For: Mixed or changing noise sources—fans, equipment, electrical noise, band noise.
Available On: FLEX-8000 and Aurora series.
Operator Notes
All filters use preset, optimized parameters — no adjustments required.
Only enable a filter when its target noise type is present.
Some filters can be used together, but excessive stacking may change audio tone or introduce artifacts.
As a rule of thumb:
NRL → Random noise
ANFL / ANFT → Tones or hum
NRF / NRS / RNN → Voice clarity enhancement