Back in the day we only had AM radio and it seemed like you could get a lot of stations during the day and at night you had trouble tuning in just one station as there were stations coming in from one end of the dial to the other. Back then I could get a lot of local stations (by local I mean those within a hundred mile radius or maybe a little farther), most of which were daylight stations. They would sign on around 6am and sign off around sundown. Now whenever I try using an AM radio, there is very little that comes in. I don't know if they have powered down the AM stations or what, but at the Ranch UP on the tundra I'm lucky if I can get one or two stations on the AM band. I have an old truck ('73 Dodge) with an AM radio (and only AM) and sometimes all I get on it is static.
When I was in High School I would listen to the radio at night because we only had one channel on the TV, sometimes the radio was more entertaining. I was UP near the shores of the big Gitchee Gummee, but at times I would tune in stations from as far away as New Orleans. Also the station in Nashville that broadcast the 'Grand Ole Opry' on Saturday nite. The station I listened to most at night (after the sun went down) was WLS from Chicago. Weeknights there was a DJ named Dick Biondi who played the popular music of the day. He is back in Chicago, now at WLS-FM and still playing the same songs. He did a song called "On top of a Pizza" sung to the tune of "On top of Old Smokie". Once early in the morning (as the sun was coming up) I managed to tune in WLS while I was on Cape Cod and was amazed it came in on my car radio.
Found the quote below on a site called eHow. It was a post about how to strenghten AM reception.
"Tips & Warnings
AM reception is usually better at night because AM radio signals bounce off the ionosphere."
Nowadays AM radio is almost all talk and I remember when the transition started. On one of the local stations there was a DJ who liked to hear himself talk more than he liked spinning records. That started the end of AM radio for me.
I thought I was really high-tech when I bought an 8-track player with a FM tuner built in. You plugged the antenna cable into the back of the player and ran another cable from it to the in-dash radio. Now I'm up to a built-in AM-FM Cassette player in my vehicle and I hardly ever put it on the AM band as there isn't anything there of interest to me. At times I have found "Classic Country" (the only kind I'll listen to as modern country sounds like a bunch of whiners, usually whining about God) on the AM side, but not lately.