Quite simple, anartificialhorizon, the radios in your C172 are (ah, how do I put this nicely) lets just say....OF POOR QUALITY.
'Tis a wonder they work at all.
Hey, I tried to be nice.
Airline standard TSO quality avionics are a different kettle of fish altogether.
Yes, even twenty five year old ones.
Gee, I wonder why....