The AM Broadcast Band runs from 535 khz to 1705 khz. AM has two types of signals that reach listeners. The "groundwave" is how most of us listen to local AM stations. The "skywave" is how we hear stations far away at night. This "skywave" signal bounces off the ionosphere and makes stations able to be heard hundreds of miles away. Here's a list of stations you may be able to hear at night.
Some Class C & D stations operate with very reduced power at night and many have "Pre-sunrise" authority to begin operation at reduced power at 6:00am local time even if this is before sunrise. This is also called "critical hours" operation. In all cases, the signals of Class A stations are supposed to be protected. In practice, many local stations operate at very reduced power at night and do little but create noise on the AM band making it impossible to hear distant stations. Perhaps the FCC would be wise to t authorize any station to operate at a power less than that used by the tower lighting at night!
Radio Broadcasting has been around for a long time. Thomas H. White has written an excellent history called Building The Broadcast Band.He has a wealth of knowledge on early broadcasting.
Because AM signals travel so far at night, you can often hear stations from hundred of miles away. Some folks like to keep track of the distant stations they've heard. You may want to write down the call letters, frequency, and some information about the programming. This log may help. If you are also a baseball fan, you might enjoy this listing of the flagship stations for major league baseball. Dave Hughes has a very nice site where he critiques AM Radio stations in the Washington Area.
The Montgomery County Public Schools are located in the Washington-Baltimore area. This list includes the local Washington stations AM Listeners are likely to find.
A company called Arbitron does for radio stations what Neilsen Media Research does for television. Here courtesy of Radio and Records is the most recent available Washington DC radio ratings. For current information about the radio industry you might try Airwaves Media a website operated by William Pfeiffer. Mr. Pfeiffer is the moderator of the usenet newsgroup rec.radio.broadcasting.
Once you've heard a distant station, you can send a reception report. Reception Reports are addressed to the Chief Engineer and should include the date, time, information on the program you heard and how the reception was. Did the station come in loud and clear or did it fade?. Was there interference? You may want to let them know you're doing this for fun and would appreciate them verifying your report.
If you want a record of your reception, you should enclose a self-addressed stamped postcard for the engineer to sign and verify your report. Some (very few) stations have their own QSL cards, but in most cases you will need to supply the card.
