AM Radio reception fades in in and out

not a radio expert but i'm old enough to remember when am radios were the only game in town. they have weaker reception than fm's and will almost always fade in and out depending on where you are. i think the reception is related to line of sight with the radio tower. try going into a parking garage or tunnel, you won't pick up anything at all. atmospheric conditions can have an effect too. i used to be able to pick up a station in alberta, canada from a tiny am transistor radio in seattle.