[Amps] Tubes <==> Neat? tspa

[John T. M. Lyles]

Kim
I dunno about tubes being neat anymore, they are 
sort of a dead end for a career path, unless you 
specialize in an area where they are still in 
wide use, such as super power RF for particle 
acceleration or plasma physics. I actually get 
paid to work with tubes, but I would have never 
thought that when I was a student 30 years ago. 
Gridded vacuum tubes are going the way of 
dial-switched telephones. I don't know of any 
young engineers who are still interested or 
obtaining degrees with any specialization related 
to thermionic tube technology, but hams are the 
'dying breed' (we are?) who still play with this 
technology at home. Heck, in a year or so I may 
even toss out my CRT at home, buying a flat TV 
finally.

I hope that there are still folks who will 
continue to make and use them for certain 
applications, as even  the broadcast engineering 
profession is loosing touch with them in all but 
UHF television transmitters, with IOTs and some 
klystrons still being used. They are certainly 
useful devices within the constraints that they 
have. Peak power doesn't seem to be much of a 
limit for gridded tubes until you pass 5 
megawatts output at VHF and even more at lower 
frequencies where the internals can still be huge.

Spangenburg wrote a good text on vacuum tubes. 
Others include Reich, Seeley, Eastman, Terman and 
many more. Each book seems to have a special area 
that they did a better job of explaining. One 
place which has popped up on the WWW has a lot of 
the classic texts copied so that all can read 
them, although you don't get the same feeling as 
you would with a moldy hardbound yellowed text 
book written in 1942 on the subject!

http://www.pmillett.com/technical_books_online.htm

Get those books for your library and keep those filaments lit.
73
John
K5PRO



>John, you get to play with some of the *neatest* stuff! 
>
>My Dad has some books on vacuum tube design and 
>characteristics.  One is by Spangenberg and he 
>has two others (can't recall the author). I was 
>reading in Spangenberg about TT filaments vs 
>oxide cathodes. I didn't see anything about 
>power cycling, but there was quite a bit in 
>there about optimal operating temperatures and 
>the ways that oxide cathodes get poisoned. 
>Pretty interesting stuff.  There was also lots 
>of stuff in there about odd-ball (to me) very 
>specialized tubes for all sorts of pulse 
>generation and high-speed switching.
>
>I needto ask my Dad if he's willing to let me have those for my library :)
>
>Cheers,
>
>Kim N5OP