🚀 go-pugleaf

In article <1993Jan7.005550.6869@kodak.kodak.com> ornitz@kodak.kodak.com (Barry x24904/ER/167B-TED) writes:
>In article <rich.726361718@pencil> rich@pencil.cs.missouri.edu 
>(Rich Winkel) writes:
>>Can anyone explain what a "Reike and Hartree diagram" is?
>
>A Rieke diagram is sort of a fancy Smith chart for representing how the load
>impedance and its point of connection to the magnetron can affect the power
>output of the tube and its frequency. 
	
	In the context of the original question (lowering the power
density in the microwave oven), this is irrelevant.  First, the
load is the contents of the microwave oven (and this can, we all know,
vary quite a lot without stalling the oven).  Second, we don't
care about the exact frequency (nor the exact power); only large 
power-output changes are of interest.
	The load would only change markedly if the feed horn
from the magnetron were altered.


>A Hartree diagram shows the theoretical minimum anode voltage at which operation
>is possible in the various modes of the magnetron.  Under operating conditions
>the anode voltage must exceed the values given in the diagram.

	This is obviously of concern.  I would have thought that the
magnetron was just a diode, and that changing the input current (by
substituting a smaller capacitor in the charge-pump power supply)
would alter the output power.  The implication here is that at too-low
voltages the magnetron doesn't oscillate.

	Again, I think this is not prohibitive: magnetrons are more than
85% efficient, and this implies that the input voltage (which is
unfiltered) is in the operating range for a substantial fraction of the
whole 60-Hz duty cycle.  That implies that the input voltage can vary 
by a factor of four or so before the magnetron stops oscillating.

	It might be impossible to get a 100:1 output power range, but
10:1 still looks reasonable.  As long as the magnetron doesn't overheat
from the current during the 'wasted' time, the microwave oven will
still operate even if the magnetron has output efficiency of zero
for most of the cycle.  It just means that the output power drops
to zero faster than proportionally to the input power.

	Think of it as reciprocity failure   :->

	John Whitmore