I wrote:
In practice, the term
"visible" often refers to light detectable by instrumentation
suitable for visible light, say from 300 nm (the atmospheric cutoff)
to 1000 nm (the intrinsic silicon limit).

In article ,
Jos Bergervoet writes:
(In the same fashion, this silicon is a 'metal' of course!)

Heh. (Silicon is a semiconductor, not a metal, for anyone who is
confused.) I reported how the language is used in practice. Human
language is not always logical. I don't think I've seen silicon
described as a metal, but it wouldn't shock me. Actually, come to
think of it, doesn't silicon become a metal at very high pressure?

950 GHz sounds like an interesting LNA design problem!
Is there any pointer to the solutions they use? (Other metals than
silicon, undoubtedly..)

There must be some design documents, but I don't know where. There
should also be descriptions in the literature. Try an ADS search.

My courses in radio astronomy were a long time ago, and the
technology has changed. I don't think there is any amplification at
the incoming frequency, though. In most radio telescopes, the signal
is mixed down to an intermediate frequency and amplified there. In
the old days, they would have used klystrons or something, but I
doubt they do now.

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