[Craiggybear]

I used to see a lot of TW tubes and it is amazing these are still vitally important and have never been surpassed in terms of gain and low noise.

Vacuum tubes (or valves here in the UK) in the high-microwave range are truly wonderful and bizarre. Some of the quantum theory involved in their operation is utterly mind-blowing.

I recall as a kid, a lot of military stuff my stepdad was involved with from Rathyon, Westinghouse and GE during the 70s was really cutting edge and has seldom been matched or bettered.