Flew IFR yesterday on a couple hour cross country trip. Radios worked fine until about the 4th handoff. Switched from center to the class c approach I was passing, called them and no answer. Tried both radios, no answer. Tried pulling out squelch, no answer. Back to the previous center frequency and was advised the class C could hear me but I didn't receive them. A little further in the trip and was handed off from 1 center frequency to another same center different frequency. Again, no reply. Back to previous center frequency and they offered a 3rd frequency to try, again no reply until I had traveled about 20 nm. Nearing destination handed off to the nearby class C approach. Could barely hear them and for a while could only hear them with squelch pulled open. Current radios are GTR 200 and 430W. Have had poor reception range and clarity issues (but seemingly not on all frequencies) since install (years). When I installed the Avidyne IFD 440 in place of the 430W its radio seemed to work very well but I only had it in the plane for 2 flights. Long ago when I had a Collins VHF 251 (using the same antenna as the 430) it worked fantastically well in clarity and range. I have changed the RG 400 cables a few years ago so doubt those are a factor. What causes poor radio range? What is the best radio you have used?