Loss will be greater on the thicker board, because a greater fraction of
the fields surrounding traces and components will be in the board
material as opposed to being in the air. Having less field in the board
material will also make your circuit less sensitive to the temperature
and humidity dependency of the board material. The actual amount of loss
or temperature/humidity sensitivity depends on a whole host of factors,
so it's hard to say how much difference it'll really make in practice.

Roy Lewallen, W7EL

MikeN wrote:
Hi

A question.

Would the in-circuit losses for RF equipment operating around 1 - 3
GHz be greater if built on 1.6mm or on 0.8mm FR4 laminate?

In particular, on which laminate thickness would a VCO in this range
be easier to get running?

Any explanation for the answers would be helpful.

Thanks

MikeN