Noise Detection and Measurement

We recognize the presence of noise primarily as we see and hear its effect on reception – what we hear, see on a spectrum display, and decode (e.g., wspr spots, CW, etc.).

Software-Defined Radios

For now, anchored in a particular HamSCI project, we will focus on the use of the RX888 which works with ka9q-radio and its supplementary software, ka9q-web, which provides a high-quality spectrum display.

Other radio systems (RTL-SDR, Airspy, HackRF, SDRplay, FobosSDR, KiwiSDR, OpenHPSDR and its descendants like FlexRadio, ApacheLabs, etc.) work or come with spectrum display software. We hope the descriptions here will prove just as useful in those environments as well.

Advantages:

  • Provides a visual spectrum and/or waterfall display of noise patterns.

  • Helps recognize constant, periodic, or intermittent interference.

  • May provide dynamic noise, min and max signals per bin, SNR, and S-meter measurements, among others.

  • Some deployments may enable use with directional and/or mobile antennas for noise hunting.

Analog Receivers (AM, SSB, CW-capable radios)

These devices can provide useful information, especially in hunting for local noise. Examples include, hand-held AM receivers, handi-talkies monitoring unsquelched 2 meters, armed with fox-hunting/RFI antennas.

Usage:

  • AM mode is highly sensitive to impulse noise.

  • SSB/CW mode helps analyze weak noise patterns.

  • Portable radios help in field noise hunting.

Oscilloscope with FFT (Fast Fourier Transform) Capability

Usage:

  • Visualizes noise signals in both time and frequency domains.

  • Helps detect transient and impulse noise sources.

Stand-alone Spectrum Analyzers

Examples: Rigol DSA815, Siglent SSA3021X, TinySA (Ultra).

Usage:

  • Measures signal strength over a range of frequencies.

  • Helps identify noise sources by their frequency signature.

Field Strength Meters

Usage:

  • Measures RF power levels at different locations.

  • Useful for determining noise intensity around potential sources.

Current Probes & RF Clamp Meters

Usage:

  • Measures common-mode current on cables and feedlines.

  • Helps detect conducted emissions from power supplies and electronics.