If the horizontal speed in Spectrum Lab isn’t changing on the scrolling plot, it’s usually because the display timing is controlled somewhere else. In Spectrum Lab, the time axis speed depends on update rate and buffer timing, not just the plotter control.
Here are the most common causes and fixes:
1️⃣ Scroll speed is limited by FFT/update rate
The horizontal scroll speed is tied to:
- FFT size
- Overlap percentage
- Sample rate
- Averaging / smoothing
If your FFT takes (for example) 500 ms per update, the plot cannot scroll faster than two updates per second — regardless of the plotter speed setting.
Check: Options → Spectrum Settings → FFT
Try:
- Reducing FFT size
- Reducing averaging
- Increasing overlap
- Increasing sample rate (if appropriate)
2️⃣ You’re adjusting the wrong display module
Spectrum Lab has multiple displays:
- Main spectrum window
- Waterfall
- Strip chart / plotter
- Custom displays
Make sure you’re adjusting the speed of the actual active display module.
Right-click inside the specific display window and check its own timing settings.
3️⃣ Time scale is fixed
If the strip chart is set to a fixed time span (e.g., 60 seconds across the screen), changing scroll speed won’t visually change anything because it rescales automatically.
Check in: Options → Display Settings → Time Axis
Look for:
- Fixed time span
- Scroll mode vs. wrap mode
4️⃣ The plot is in “Wrap” mode instead of “Scroll” mode
If enabled, it fills the screen left to right then restarts. Changing speed won’t look like scrolling.
Switch to continuous scroll if desired.
5️⃣ Update interval is fixed in the configuration
Check:
Options → System / Performance → Display refresh rate
If refresh is capped (e.g., 1 Hz), the plot cannot scroll faster.
Quick Diagnostic Test
Try this:
- Reduce FFT size drastically (e.g., 4096 → 1024)
- Turn off averaging
- Increase display refresh rate
- Then adjust horizontal speed
If the plot speed changes now, the issue was FFT/update latency.