[Radio Wrangler]

The X and Y plates are not in the same place along the tube.

The Y plates get the electron beam first and the angular deflection they make subtends a greater movement of the spot on the screen.

The X plates come next and they have to be larger to accommodate the deflection from the Y plates, so they have more capacitance as well as lower deflection sensitivity.

In an oscilloscope, having more sensitive Y plates means the Y amp doesn't have to work so hard or swing so far. This helps tha bandwidth. The lower capacitance deflector plates help too. The X deflection doesn't need the same bandwidth normally, and so the X amp can be made slower and wider swinging.

The circuit diagram shows asymmetric drive to both the Y and X plates. This can make the deflection non-linear to a visible extent, and also affect brightness and focus as the spot is moved from the centre. Better circuits use long-tailed pair balanced amplifiers to drive both Y plates and both X plates.

David