RF Field Guide · reviewed reference
Channel widths, protocols, polarity, and MIMO
Capacity depends on usable spectrum and signal quality, not a channel-width setting alone.
Question
Why can a wider channel or more spatial streams make a link worse?
Inputs
- Channel width and adjacent-channel environment
- Protocol, modulation/coding, antenna polarization, and spatial-stream capability
Answer
Working
Thermal noise rises with bandwidth: N = −174 dBm/Hz + 10 log10(B in Hz) + receiver noise figure. Doubling bandwidth raises the thermal-noise power by 3 dB, so the additional throughput must justify the signal-quality and spectrum trade-off.
Visual explanation
- Channel width
- Noise bandwidth
- SINR
- MCS
- Spatial streams
- Throughput
Interpretation
Plan a channel width from measured spectrum conditions and required capacity. Confirm polarization alignment and use the radio's actual MCS table rather than a marketing PHY-rate headline.