Check out RF Micro Devices DKFC5072A development board. This is a mixer and synthesizer that is programmable via a USB cable. It's rated up to 6 GHz and could form the basis of a universal transverter, just add appropriate filters and amps. I have used the older version up to 2.5 GHz and they work pretty good. The development board is $210.00.

- Howie AB2S