Dave Platt wrote:
According to a talk I saw recently, commercial television broadcasters
have moved almost exclusively to solid-state RF amplifiers for their
newer stations.

I suppose this is kinda OT but tubes (usually, klystrons or various
modifications thereof) are still generally used for high power at UHF.
IIRC solid-state UHF transmitters are available up to about 30kw or so,
but larger stations require as much as 110kw to achieve the desired
effective radiated power.

Tubes do indeed seem to be a thing of the past at VHF, where powers
beyond 50kw are generally not necessary.
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com