why are smaller cathode ray tube displays still almost as long as large ones? do the electrons need a certain distance to get up to speed or some shit? is it that you can’t deflect them accurately over a short distance

@jk it requires a much smaller change in the position of the electron beam for a longer tube than for a short tube. So for a set dpi you want to have the same length tube regardless of the number of points so that the control hardware to control the electron beam can be the same in each tube instead of having to make a new one for each type.

@jk you also need to focus the electron beam (which is even more complicated on color tubes), I think that's the reason

@jk I'm guessing but it could be something to do with the current load of packing a suitable magnetic field into a shorter distance.

@jk Short answer: physics (that you can't overcome without getting wildly expensive). In order to get beam convergence and focusing (terms of art: dynamic convergence and color purity) it really really helps to make the thing long. The more you shorten it the tighter your tolerances have to get and the more factory calibration (deflection yokes, etc.) or dynamic adjustment (power electronics and such) you have to provide.

@jk As you shrink the display area, you're rarely dropping the resolution, so the tolerances for focusing, etc., get *tighter*. So while you should be able to shrink the length because of scale, you have to keep it long because you need better aim. On a giant screen your shadow mask can have considerably larger holes than on a little screen.

@jk pretty much you can't put the big magnetic field to close to either end of the electron's path and it can only bend a few degrees per depth.

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