[Amps] Incandescent and tube filaments tspa

[Kimberly Elmore]

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

----- Original Message ----
From: John T. M. Lyles <jtml at lanl.gov>
To: amps at contesting.com
Sent: Wednesday, February 14, 2007 1:18:38 PM
Subject: [Amps] Incandescent and tube filaments tspa

One thing to consider when comparing these, is that the filament in a 
lamp is lit to incandescence, higher temperature, than the filament 
in a TT or oxide cathode filament. These are typically less than 
2000K, dull orange or less for oxide cathode. Also, the light bulb 
filament, does it use thoria in it or is it pure tungsten? Way 
different mechancially. Finally, the light bulb filament, in my 
recollection, is coiled like a tiny spring, or so i thought. Tube 
filaments are bars, strands, sometimes coils, but much different 
geometry. In some tubes they are tensioned with a mechanism to allow 
for changing dimensions when they warm up.

John
K5PRO