Visual Guide to the Frequency Scale

Let's start by referencing the scale against a peak of known frequency. Create a mark with Cmd-click and drag it at the center of the reference line. Open the dialog “Format/Axes & Scales”. Enter the reference value. Click on the “OK” button.

Here's the result:

The mechanism to calibrate the Y scale is similar.
Instead of the vertical mark,
create an horizontal mark with Alt-click.
Continue as above.

keyboard commands

H or h : scale in Hz

p : scale in ppm

apostrophe : peak-picking in Hz

(press again to revert)

g : grid

(press again to hide)

T : transposition

swaps the X with the Y

be sure it's an upper-case T !