The A.Sys frequency shifter is about £700, so yes it is very
expensive.
Excuse my ignorance, but what is the difference between a Bode type
f.shifter and a normal one It is not simply linear and exp. kind of
differnce, is it

I did not see anything in the Modcan frequency shifter page, that
would clasiffy it as a Bode type.

Peace out.