DSO2D10: FFT - wrong frequncy scale when Mem Depth is larger than 4K

filipj

I was doing FFT od the reference signal of the oscilloscope (square wave, 5V, 1kHz)
As long as the memory depth is set to 4kpt the FFT of the signal seems to be correct (measuring with time base 1ms).
However when I change the memory depth to larger value the scale of the FFT changes and the spectre plot seems to stay the same.
It shows spectre on  negative frequencies, this seems to be incorrect.