Some variables are made to work at 1GHz+. For example a triple ganged
cermet trimmer was very common in cable distribution boxes (trunk etc) a
few years ago. The 3 R's varied together and implemented a PI or T
unbalanced continuously variable 75 Ohm attenuator. Very usefull. I
suspect (but do not know) that they used to cost about $5 at the factory
gate. But I do not know for sure. They were pretty good but needed
occasional cleaning as any mechanical contacts do.

Peter

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.