[R-390] Tube shape

[Roger L Ruszkowski]

Looking at the site showing how the 300Bs are made me wonder why the 300B
and other tubes have their characteristic shape.  Is this for better
cooling?  I suppose increasing the glass area would help dissipate more
heat, but is there something about the expanded shape that aids air
convection around the envelope?

Just wondering...

Barry(III) - N4BUQ
-------------------------------------------

Scott,

Oh, Curse another science question.

Think of it as a best effort to get all the glass an equal distance from
the
heat source.

So all the heat reaches the glass at the same temperature.
You know the same field straight because it is the same distance from
the antenna.

Thus there is less heat moving side ways in the glass.
Heat would like to move sideways in the glass to let all
glass be at same temperature.

Heat in the vacuum is a radiation problem.
Heat in the glass is a conduction problem.
Heat radiation from the glass to the air is not
the same (but is similar to) as the radiation
from the elements to the glass through vacuum.

No real hot spot around the center band of the tube.
If you can imagine the middle of a 300 as
not being hot.

Cherry up those plates one time and you could watch your
300 implode if it were not for the bottle shape.

____________________________________________
Then again,
If we put more nothing in the bottle and get it,
is there then less stuff to bump around in there and make noise?

Does the exta space help or hinder getting the gas out?

Roger.