[Boatanchors] 6BE6 VFO/Mixer Tube

[Ian Wilson]

Imagine sawing off the top 2/3 of the tube. This leaves you with something
that
looks a lot like a triode: cathode, grid 1, and part of the first screen
(grid 2).

You can build an oscillator using this triode using any of the standard
oscillator
configurations.

Now put back the top part of the tube. The electron beam passes through g2
and the rest of the tube appears like a pentode (with some funny screening).
However, the electron beam varies in time owing to the oscillator built
using
the lower part of the tube. The signal grid (grid 3 I think) then in turn
modulates
the electron beam. The resulting current into the plate is formed partly
from the
product of the signals at g1 and g3. Using a tuned circuit in the plate
allows
the desired mixer terms to be extracted from the unwanted terms.

73, ian K3IMW