HP35660A just like in the video. I repeated the same experiment using the 50 ohm terminator and got the same results, but after reduce the span I noticed the cutoff frequency of the 1/f noise also reduced. I understand swept spectrum analyzers much more than this 35660A, but am trying to learn... It appears the 1/f noise measurement is responding like resolution bandwidth is changing, but isn't the PSD measurement supposed to use a 1Hz bandwidth? There is no RBW setting on this instrument. Example of 100Hz and 1.6kHz span below. Note the corner frequency seems to move from about 20 Hz to less than 1 Hz even though no settings changed other than span and re-acquiring an average of 10 samples: