Modern Electronics (was Re: List charter mods & headcount... ;

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Mon Jun 21 17:42:37 2004

> 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
Received on Mon Jun 21 2004 - 17:42:37 BST