I have an old fedder thermostat that I want to replace with a new digital one. The old one has H (blue wire connected) V (white wire connected) C (green wire) and F (red wire) the new stat has rh rc(jumpered) W why G. How do the new letters maatch up to the old H,V,C,F ones?

You might need to go to furnace end and see what color ataches to which connecting,, for instance the red wire connected to transformer/or a 24V post,, ETC,, there's not much of any way we could help you from this distance and without knowing what kind of furnace you have and the model number

Good luck