To what does the term "panadapter" refer? (Physical hardware or software?) How did the term "panadapter" originate as related to radios or electronics?
How is the term "panadapter" different from the spectrum and/or spectrum waterfall display on an expensive receiver/transceiver or an SDR software application? Or is the term a superset of subset of those?
A panadapter is a device that adapts the narrow (typically 4kHz) bandwidth of a traditional receiver into a much wider bandwidth, perhaps the entire band. The pan- prefix means all, as in panoramic, pandemic, or Pangaea.
A waterfall display isn't a panadapter, though a panadapter may have a waterfall display built in. A spectrum analyzer can also make a waterfall, but the waterfall isn't the spectrum analyzer.
Since most SDRs have relatively wide bandwidths, they can be used as panadapters. Many panadapters today are based on the RTL SDR design, tuned to the receiver's IF and inserted just prior to the filter.
An SDR used as a standalone receiver would not be a panadapter: there's nothing to adapt.
