In LTspice, why doesn't the FFT plot update after a simulation?

Question

I'm using LTspiceXVII (17.0.35.0). I run a simulation and make an FFT plot. Then I change a parameter and the time waveform updates, but the FFT plot doesn't update. I have only been able to see the updated results by creating a new FFT plot. How do I get the existing FFT plot to update?

9/27/22 Follow up edit: After making updates to the FFT window, I saved the settings in a .plt file with these contents:

[FFT of time domain data]
{
  Npanes: 1
  {
     traces: 1 {524290,0,"V(out)"}
     X: ('M',0,10000,4.999e+006,5e+007)
     Y[0]: (' ',0,1e-008,20,1)
     Y[1]: ('K',0,-30000,30000,300000)
     Log: 1 2 0
     GridStyle: 1
     PltMag: 1
  }
}

I pulled up a new FFT window on a new set of data and tried to apply these settings to the new FFT window by clicking the space bar. I got this error:

How do I apply the saved FFT settings to a new FFT plot?

Answer 1

Since you had to manually perform an FFT after the simulation, it follows that you have to repeat the process everytime you need an FFT. There is no automatic process. If you're worried that you may lose the FFT plots, don't close the windows. If you need different FFT plots in the same window then you have two choices:

1. use a .STEP, if your circuit allows, or
2. export the data then collate the results.