Dear all Thinking about this - I presume the first LO has to cover 1000 - 2000 MHz Not too many VCOs will do this - thie only one that fits the bill is the ROS 2150VW which we used in our PLL board a few years ago. The ROS 1500 in the SSA looks like it only goes 1-1.5 GHz The 2150VW would be a suitable choice I presume Richard