WiFi Channel Analysis and Spectrum Survey

~100 min7 Steps

Use SDR and WiFi monitoring tools to map channel congestion, identify interference sources, measure signal coverage, and produce actionable channel recommendations.

Prerequisites
Gather these before starting the workshop
  • RTL-SDR (for sub-2 GHz analysis) or HackRF One (for 2.4/5 GHz)
  • WiFi adapter with monitor mode support (e.g., Alfa AWUS036ACH)
  • SDR++ or GQRX installed
  • Kismet or Aircrack-ng suite for packet-level analysis
  • Floor plan or sketch of the survey area
Step 1 of 714% complete
WiFi Spectrum Overview: 2.4, 5, and 6 GHz Bands
15 min
Step 1

The 2.4 GHz band has only 3 non-overlapping 20 MHz channels (1, 6, 11 in the US). Every other channel partially overlaps with neighbors, causing co-channel and adjacent-channel interference. The 5 GHz band has 25+ non-overlapping channels — far less congested in most environments.

WiFi operates across three unlicensed frequency bands, each with different propagation characteristics, channel plans, and interference environments. Understanding the spectrum layout is essential before performing a site survey.

2.4 GHz (802.11b/g/n/ax)

2.400–2.4835 GHz

Channels: 14 channels (1–14), 22 MHz wide, 5 MHz spacing

Non-overlapping: 3 in US/Canada (1, 6, 11), 4 in Europe/Japan (1, 5, 9, 13)

Max BW: 40 MHz (802.11n), rarely used due to congestion

+ Better wall penetration, longer range, legacy device support

− Heavily congested in apartments/offices. Competes with Bluetooth, microwave ovens, baby monitors, Zigbee.

5 GHz (802.11a/n/ac/ax)

5.150–5.850 GHz (varies by country)

Channels: U-NII-1/2/2e/3 sub-bands, 20 MHz channels numbered by center freq

Non-overlapping: 25 non-overlapping 20 MHz channels (more with channel bonding limitations)

Max BW: 80 or 160 MHz (802.11ac/ax)

+ Much less congested. Higher data rates with wider channels. Better for dense deployments.

− Shorter range. Some channels require DFS (radar detection). Fewer legacy devices.

6 GHz (802.11ax / WiFi 6E, WiFi 7)

5.925–7.125 GHz

Channels: 59 non-overlapping 20 MHz channels, or 7 non-overlapping 160 MHz channels

Non-overlapping: 59 channels at 20 MHz, 29 at 40 MHz, 14 at 80 MHz, 7 at 160 MHz

Max BW: 320 MHz (WiFi 7)

+ Virtually no legacy interference. Enormous channel availability. Future of high-density WiFi.

− RTL-SDR cannot receive above ~1.7 GHz. HackRF required for 5/6 GHz survey. Short range.