[R-390] Noise Floor question

[Bill Hawkins]

What you're looking for is thermal or Johnson noise. Try this:

http://www.dataforth.com/catalog/doc_1065.html

The first RF tube contributes noise because it is hot. Wonder what
you could do to the noise figure of a 390 class set just by FETing
the first RF? Don't even think of it if you're a purist or concerned
about overload capability. But if noise is your first concern ...

Bill Hawkins