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G0TEZ > TECH 04.09.05 14:32l 73 Lines 3026 Bytes #999 (0) @ WW
BID : 65466-GB7FCR
Read: GUEST DL1LCA OE7FMI
Subj: Why vacuum tubes?
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Sent: 050904/1227Z @:GB7FCR.#16.GBR.EU #:65466 [Blackpool] FBB-7.03a $:65466-GB
From: G0TEZ@GB7FCR.#16.GBR.EU
To : TECH@WW
When I was young there was no internet and, in my area, no public
libraries with any scientific books so learning was a matter of picking up
what you could from old books.
My boyhood standby was THe Harmsworth Self Educator from 1900 or earlier.
It was a great help on steam engines, bridges,ships etc., but nothing
about
petrol engines or electricity.for that i had a mixture of books, all old.
From these I found out about electrocity and wireless, even telvision. It
is not generally accepted now that other people besid Baird were inventing
mechanical TV.
According to which book you read, you could say that Frank Whittle or the
team from heinkel invented the jet engine in 1936. The truth, as far as I
can tell, is that both people invented it at the same time as they are too
different to be copies of each other. There were copies and some were
hilarious; the Italians, among others, only had the vaguest idea of what a
jet engine might be so the constructed an aeroplane with a normal engine
inside a tube and said that was a jet engine.
A lot of this stuff is forgotten.
I used to wonder about the electric light bulb. Not about who invented it
but why, out of the several inventors working on it, all had the idea of
creating a vacuum so that oxygen in the air didn't burn up the filament.
19th century scientists knew about inert gasses so, surely it would have
made more sense to just fill a bulb with, say, nitrogen which could push
out the oxygen. Even simpler, would be to connect your bulb containing
it's filament to another airproof container and set fire to something in
it, even paper burning at 451 deg F would remove the oxygen from both
containers, then you melt the glass tube at the top of the bulb and,
presto! no oxygen, filament won't burn.
A whole lot simpler and cheaper than making a pump to try to create a
vacuum.
Better than paper would have been magnesium which was used in valves to
remove the last of the oxygen when the pump had sone it's work, a process
called 'gettering' if I remember clearly.
There is a bit of a twist here. If the electric light had been invented as
a bulb full of inert gas at normal pressure then vacuum tubes, valves,
would not have come into being as gas stops electrons.
Would they have gone straight to solid state electronics? Food for
thought.
I seem to remember a TV programme a couple of years ago which said that
Joseph Swann experimented with bulbs full of inert gas but his bulbs kept
in museums are all of the vacuum variety to my knowledge. I don't know if
he knew about neon,Argon,Krypton and Xenon but he did know about Nitrogen
and could even have used carbon monoxide.
I'm not sure but I think it was our well known presenter, Adam Hart Davis.
If so, the programme will almost certainly come around again:-
As for TV, whether you believe in JLB or EMI or someone else; whoever
invented TV also invented repeats.
73 - Ian, G0TEZ @ GB7FCR
Message timed: 07:52 GMT on 2005-Aug-31
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