do electron tubes really need to be vacuum packed?

Question

is this the reason why home made electron tubes aren't as good as the ones that are made in the factory or is it another reason

Answer 1

The electrons that are boiled off the cathode by the filament need to go through the vacuum to easily get to the anode. Also if the hot filament touches air inside the tube then it can burn through. Factory-made tubes have a vacuum and also have a "getter" a metallic plate to attract any leftover oxygen molecules.

Answer 2

if you leave air in the tube, something bad will happen when the filament heats. air being a gas will try to expand and will break the bulb. bright lightbulb filaments operate at higher temperature and they will oxidize from reation with the air and extinguish before the bulb explodes. That why ordinary light bulbs are also in vacuum.

so called "cold cathode" tubes replace air with a non-reactive gas, such as neon. without the filament, they do not get hot enough to explode. they do not work as amplifiers so they are not to useful for most projects.

you can make perfectly good tubes at home, but you do need a vacuum pump and a getter. a number of useful tube types do not require a high vacuum. early tubes were all hand made and that technology can be replicated at home. for example many radio hobbyists have made their own '01 tubes to use in antique radios. more modern factory designs allow for tubes to be miniturized and have multiple sections and can only be assemble with machinery.

Answer 3

electron guns in a tube fire electrons at the screen....

any atoms in the tube interfere with the trajectory of the electron beam fired at the screen....

so the greater the vacume the less atoms in the tube to interfere with the beam....