21 Jun
2004
21 Jun
'04
10:42 a.m.
Aside from legacy electronics (I have some
pre-transistor-era equipment
lying around), for which transistor versions exist, I can't think of
any. The only thing I'm not sure of is the microwave oven - does the
microwave-generation-thingy depend on vacuum?
We said knowledge was being lost, now I am sure of it.
Yes, the microwave generator in a microwave oven is a cavity magnetron,
which is a type of vacuum tube. It's close to a directly heated diode
with a strange shaped anode block (incorporating the resonant cavities)
and a magnetic field along the axis of the device.
Certainly television and radio do not depend on vacuum
tubes today
(well, certainly not on the receiving end; the technology exists to
transmit with transistors, but I don't know whether it can handle the
power levels appropriate to mass broadcasting).
I am almost sure the trnasmitter output stages are still valve-based, at
least on larger transmitters.
Radar - as above: the power transmitting stage may still be vacuum
tube, but certainly _could_ be transistor; the rest definitely can be.
I wouldn't want to bet on that. I certainly wouldn't want to try to
design a microwave oscillator using semiconductors of sufficient power
for a large radar system.
-tony