different models of GDOs from 47
different manufacturers-not counting 7 homebrew units. I am looking for
a nice Millen 90662-A;
and... anything else you don't
see listed here!!!
My Millen collection is now complete: I obtained Millen 90662-A SN:15
look at my
CORROSION TOPICS page. Lots
unfortunate mistakes and cures. Complete with closeups!!!
Wavemeters-and for some reason I'm
not real sure of yet: BC-221s..
I guess I'm looking for the 'perfect
Grid Dip Oscillators (Meters)
function by detecting resonance in a circuit-under-test.
Essentially, they are calibrated variable oscillators. The plugged-in
coil of the GDO,
as a feedback element of the oscillator, determines the range of
oscillation, and is coupled to the coil of the circuit-under-test. When
the GDO is
tuned to the same frequency as the circuit-under-test, the current of
the GDO is
reduced, and this "dip" in the GDO's
current is shown on its meter.
Originally a tube-type
oscillator, the absorption of the feedback signal to the tube's grid
reduced the overall current drawn by the oscillator, and hence the name:
great reference to GDO operation can be found at
Also I have a few
a very nice Millen.