--- Terry Blanton wrote from Fran Grimers interesting
thoughts on the cavity magnetron....
> A cursory google does not return the COP of a
> magnetron. Has anyone seen it measured?
I have seen the figure of 70% eff for the oven-type
units, but do not have a handy reference. The main
losses are cathode heating and tube heating. Many
tubes are heavily finned to dissipate heat. The
magnetron was definitely amazing in comparison to
radio tubes ("valves" to the Brits), because normal
tubes in the 1940s were around 20-40% eff. while the
magnetron was nearly double that. Some of the higher
eff. is due to higher power - as all RF tubes get more
eff. in general, as they get larger, since the cathode
heating losses are less, percentagewise.
I suppose that an electric --> electric COP of .8 is
possible with a cold cathode magnetron of a kilowatt
RF output. Maybe higher for certain uses - as they
have been proposed as a way to get solar energy back
to earth from orbiting satellites. The ground antenna
would be 95% so the net would be ~75% which doesn't
sound that good untill you realize that even if copper
wires would stretch that far (~22,000 miles), they
would likely not do much better.
Jones
