Read the spectrum and waterfall
The spectrum is an immediate view of signal power. The waterfall adds time, which helps you identify activity and drift.
Read signal level
Peaks above the noise floor usually indicate signals. A narrow fixed line can be a carrier, a birdie, or center-frequency interference.
Use the receiver passband overlay to see which energy enters the demodulator. Tune or change the passband when adjacent energy enters it.
Change the view
Open Settings > Spectrum to set the display Floor and Range, the waterfall Scroll speed and Waterfall row height, and the View span.
New settings use a scroll speed of 30 rows/s. You can choose between 20 and 120 rows/s. Existing saved speeds are preserved.
The same page sets trace Smoothing, Peak hold, and the waterfall Color palette.
Follow the background level
Select Auto beside Floor, or turn on Automatic floor in Settings > Spectrum. Auto follows the received background in the visible RF span. It holds during transmission or missing data.
Turn Auto off to hold the current floor. Moving Floor also returns to manual control. Range stays manual. These are display controls and do not change receiver gain.
RF and FSK save separate floor, range, Auto and palette settings. Configure the FSK waterfall from its own toolbar or settings page.
Pan and zoom
Zoom changes the displayed span. Panning moves the view center while keeping the receive passband visible.
With a live SDR, these actions can retune the capture to cover the new view. Scale dragging groups hardware retunes at roughly 100 ms intervals and applies the final position when you release the mouse.
A capture retune can interrupt sample history while the source settles. It does not necessarily mean that the receiver disconnected. Read capture, view, and receiver frequency before diagnosing an unexpected retune.
| Action | Control | Result |
|---|---|---|
| Tune to a signal | Click the spectrum or waterfall | Moves the receiver VFO. |
| Follow a signal | Drag the VFO in the spectrum or waterfall | Moves the VFO continuously. Live reception can pan near the display edge. |
| Pan the view | Drag the frequency scale horizontally | Moves the view, with automatic capture retuning when needed. |
| Zoom | Change SPAN above the display |
Changes the visible frequency width. |
| Resize the plots | Drag the lower edge of the spectrum vertically | Changes the space shared by spectrum and waterfall. |
IQ playback stays within the recorded span when center metadata is known. KiwiSDR remote-spectrum browsing can move independently of its narrower IQ capture.
Ordinary RF pan and zoom are locked during IQ recording. Stop the recording before changing them. KiwiSDR remote-display browsing remains independent of that capture lock.
Change appearance and rendering
Open Settings > Spectrum and expand Appearance and rendering.
| Control | Effect |
|---|---|
FFT window |
Changes the balance between frequency selectivity and the visibility of weak signals beside strong ones. |
Waterfall row height |
Taller rows scroll faster and show less history. |
| Carrier and passband controls | Set the color, width, fill, and outline of the VFO marker and receive passband. |
| Trace controls | Set the spectrum line color, line width, and area fill. |
Appearance defaults |
Restores the default VFO marker and trace styling. |
Radio Bench uses a fixed analysis resolution, so there is no FFT size control. With a KiwiSDR remote spectrum, the station sets the FFT window.
Show the receive level bar
Turn on RX level bar in Settings > Spectrum > SIGNAL METER to show relative signal level in the receive passband. Gain changes the reading. RX volume does not.