ft tester

[Mike Watterson]

Goofed - it is fT that is important for RF oscillators, NOT hfe.

Well, both, depending on the Q and overall loss of the circuit.
So a low loss high Q design will oscillate closer to fT. A circuit less well matched to transistor input and output impedance will need more device gain.

There are GaAs transistors, some as low as 1.5V supply, that are up to 400 GHz. LNBs are a cheap domestic product with transistor that have to give gain at 12 GHz for Ku and 22 GHz for Ka (I have one Ka LNB).