I don't know nothing about frequncy you can use in USA but me and my friends we use bike to bike radio with earphon and mic installed into helmets.
at the beginning we use VOX but it make us crazy due to engine and wind noise that is too much variable ... it's impossible to have a right setting on VOX sistems
so we changed to PTT with a switch on the handle bar and it works great
our radios are like toys ... at very low price ( 20 euros for 2 radio) but they have a short 'working range'.
