Subject: Is it easier to tune into a station approaching it from certain frequencies

I frequently notice that the automatic tuner in my car can pick up a radio 
station if approaching it from one direction but not if approaching it from 
the other. (I can't recall if it is easier from a higher or a lower frequency--
perhaps it even varies?) If this isn't just chance, what causes it? 

I was asked to review your archives and found questions concerning "antenna 
direction," but all relating to the physical direction that an antenna is 
pointing--different from my question, as I hope my revised title will make 
clear.

Thank you for this wonderful service.

Re: Is it easier to tune into a station approaching it from certain frequencies