Radio Channel
In the US on the 72 Mhz band on a national basis you will find all the channels used. Sometimes on a local scale at one field there can tend to be grouping of channel use for no logical reason. And on a local basis there also can be certain channels affected by interferance from paid, lisensed primary industrial users which use channels in between the model channels all through the band.
Its for this reason that you should check and inquire locally at the site where you will be flying. The net will not be of much help in that regard.
John