Excerpted from private email from Ed Lyon. Ed explains the operation of the NU multiplier tube in connection with a possible new application for the tube as an alternative to the extraordinary design of a Double Reflex Super-Heterodyne radio by Robert Weaver. An alternative discussion ot Robert's radio is also available at the Radio Museum.


From: "Ed Lyon"

To: "'Joe Sousa'" 

Date: Tue, 7 Apr 2009 08:53:10 -0400


If it's elegance you like, how about this for a single-plate sheet-beam tube doing what Bob Weaver did:

1. Use the National Union experimental tube I think I told you about over a year ago.  It had a cathode, control grid, beam-forming electrodes, and deflection plates, like Bob's. But the plate was J-shaped, sort of like the sketch in the attachment here, with a screen grid inside the "J."

2. Undeflected, the electron stream strikes both the plain tantalum part of the plate and the left part, which is PbO coated to make it a dynode, rich in secondary emission.  Electrons emitted here go to the screen.  The net plate current is zero.

3. Upon deflection, the electron stream moves to the dynode side or the plain side, depending on deflection direction, and the degree of motion depends on deflection voltage magnitude.  This makes the plate current vary about zero, with the plate voltage rising above B+ for leftward deflection (in the sketch), and below B+ for rightward deflection.  The screen current does the opposite, but only reaches zero for full rightward deflection.

4. So, one could reproduce Bob's circuit, and get the push-pull output (the L.O. and the first IF output) from a balanced transformer, just like Bob's but driven by the plate and screen, which, in the National Union tube, produce complementary currents, upon deflection, but common-mode currents, upon control-grid action.  So it looks like a single-ended tube, but actually makes a balanced output.  How's that for stumbled-upon elegance?

We used these N.U. tubes for four-quadrant multipliers in the analog computer days of 1954-55.  N.U. made about fifty of them for us.  I think I may still have one, somewhere.... wish I knew where.