[njharman]

Also less prone to EMP from nukes.

[protomyth]

True, also a well understood technology that they would have no trouble producing.

[bigiain]

I bet it's only "well understood" by a very small group of people in 2015.

On the other hand, at least it's _possible_ to make your own at home: http://makezine.com/2008/01/07/make-your-own-vacuum-tube/

I somehow doubt there's many talented amateurs assembling MOSFETs in their garages...

[protomyth]

Perhaps I should have said "institutional experience", but the number of people creating fighter radars at the time were not exactly numerous.