Re: Vacuum Tubes

• To: tesla-at-pupman-dot-com
• Subject: Re: Vacuum Tubes
• From: "Stephen G. Stanton" <ulflyer-at-i-cafe-dot-net> (by way of Terry Fritz <terryf-at-verinet-dot-com>)
• Date: Wed, 21 Oct 1998 17:41:30 -0600
• Approved: terryf-at-verinet-dot-com

Reinhard,

I don't know the reason for the two sets of filaments in the 304 tubes. 
The elements are arranged with separate filament, grid and plate in a 3-6-9
12 o'clock configuration, the grids and plates connected to common
terminals.   Looks rather like a 4-leaf clover from the top of the tube.
The grid exits near the bottom of the tube; the plate out the top.

I have heard that some amateurs used to light up one of the pairs of
elements, leaving the other two dark, to be used as neutralizing capacitor
in a Class C rf amp.  I don't know much more about this tube.  The 304TL
was used extensively as a radar modulator in WW II, they were plentiful
after the war in surplus markets, but lately have become quite pricey.  I'm
always on the lookout for a spare or two for my modulator deck.

Stephen KJ6LH

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