Questions about panadapters, waterfall displays, band scopes, or any other equipment that displays a plot of RF power vs. frequency. For test equipment, use the specific tag [spectrum-analyzer].

A panadapter, spectrum scope, or band scope, is a device used with, or built into, a radio receiver, which displays the amount of RF power received across a range of frequencies, for the purpose of observing finding signals to receive (or to avoid when transmitting).

Panadapters generally work by processing the downconverted intermediate-frequency signal from a superheterodyne receiver (or IQ baseband from a direct conversion receiver); an added output for a panadapter is sometimes known as an “IF tap”.

There are two common visual representations of the data, often presented together:

  • A line chart, in which frequency is on the horizontal axis and logarithmic (dB) RF power is on the vertical axis.

  • A waterfall display, or spectrogram, which displays power as brightness (or color) instead of position and uses the vertical axis for time, displaying the presence of signals over a short time period. It usually moves downward (present time at the top, history below), hence the name “waterfall”, and may be accompanied by a line chart using the same frequency scale.

A is RF test equipment whose primary function is to display the spectrum in the same way, but is calibrated (displaying accurate absolute power level), and may have additional features for measuring or demodulating signals, but is not primarily intended as a receiver.