Mode, Bandwidth & Span

Demodulation Mode

Auto heads the Mode list on every radio, followed by AM, NFM, and WFM. USB, LSB, and CW only appear for HF-capable hardware — SDRplay, AirspyHF, Fobos, or an RTL-SDR in direct-sampling mode. A standard Airspy (R2/Mini) is VHF/UHF-only and won’t show these modes; you’ll see a note explaining why if that’s the case.

With Auto selected, the engine listens to each squelch opening and picks AM, NFM, DMR or WFM for it. The mode it chose shows beside the Mode box — Auto… while it’s deciding, then for example WFM · auto. Auto isn’t offered for SSB or CW, which have no carrier to measure. See Auto Mode for how it decides.

Bandwidth

An editable box with mode-appropriate presets — you can pick one or type your own value. WFM and CW use a fixed filter width and can’t be adjusted, and on Auto the bandwidth is the engine’s to choose, so the box is greyed out. Switching demod modes resets bandwidth to a sensible default for that mode.

Span

Span sets how wide a slice of spectrum you’re viewing (and, on some hardware, actually capturing) — narrower spans give a tighter view with a lower noise floor (more sensitivity), wider spans give you more of a panoramic view at the cost of some sensitivity. The maximum span available depends on your specific radio.