Is there a strong signal in your area?
Daytime Stations and Reduced Night-Time Power If your favorite station is a small daytime only station, you won't be able to receive it after sunset. While this may seem obvious, you would be surprised at how many folks come to me because they can't pick up a particular station at night, and it turns out to be a daytimer. Some stations don't go off the air altogether, but reduce their power to very low levels, and can't be picked up more than a few miles away after dark. If you are not sure if your favorite station shuts down or reduces power at night, you can call the station, or check the station databases I have links to on the main radio page.
Small Transmitters Sometimes an AM station station may be broadcasting with low-power, and just not reach your location. While having a good radio and antenna is important, there has to be some signal in the air for your radio to pick up to begin with. Again, many people don't realize this is the case.
Even the Frequency Matters The station's spot on the dial matters, too. Signals at the low end of the dial (down towards 540) propogate better than signals at the high end of the dial (up around 1600). Therefore, even if two stations are located in the same area, and have equally good antennas, the station at the low end of the dial will cover a greater area.
Directional Transmitter Antennas and Stations with Directional Nighttime Patterns Many radio stations have directional antennas; that is, they concentrate the signal in one direction or towards a particular geographic area. This is often done to prevent interference to other staions in the area, or to concentrate the signal where the greatest number of people may live. For example, the huge 50,000 watt WBZ near my home town has an antenna that beams the signal west-- which makes good sense, since there is no point in wasting power broadcasting out over the Atlantic Ocean! Likewise, the little college FM station that I was on (Oh! Those carefree college days!) beams it's signal to the south, to avoid interfering with another station close on the dial to the north of us. AM stations do this also. One local AM station in my area has a respectable 5,000 watts in the daytime, but the antenna system is so directional that most of the signal goes out over the ocean. They're feeding the fish, or that's the joke among some local radio engineers!
This sometimes explains why your friend who lives the same distance in miles from the station, only a few towns over, can get the station while you can't. It may be the station's antenna is aimed at his or her town, and away from yours. So, try to determine where you are in relation to the station's transmitter-- not just in terms of distance, but also in terms of direction? Again, a call to the station or search on the databases I've linked to may answer this question for you.
To make things even more intersesting, sometimes a station has to change its directional pattern at night. That is, either in place of reducing their power, or in addition to reducing their power, they may also have to change their broadcast pattern at night. One station in my area has an omnidirectional pattern in the daytime (broadcasting equally in all directions) but at night must not only lower its power, but also has to beam its signal to the east to protect stations toward the west from interference. This means people to the west of the station lose it when the sun goes down.
Obstructions between You and the Transmitter An obstruction between you and the transmitter, such as a mountain or tall buildings sometimes blocks the signal. And as I explain below, the construction of your house or office may block AM radio waves.
Where is the transmitter? Sometimes the transmitter is located in a different city from the studio. For example, the transmitter for 680 WRKO Boston, Massachusetts is a few miles west of the city in a town called Burlington. And the transmitter for 1030 WBZ Boston is a few miles to the south-east in the town of Hull, Massachusetts. Getting certain "Boston" FM and AM stations I like is a challenge as many are located as far as 25 miles north of Boston! (And I, obviously, live 30 miles to the south.) Those extra miles can make a difference. Just because a station says on the air that they're in "Your City" doesn't mean much for reception becasue their transmitter and antenna may be in "East Overshoe." Why do they do this? Well, first of all, where are you going to put up four 500 foot tall antenna towers in the middle of a city, and second, the prestige of being associated with a bigger town or city lends to the station a certain air of authority that can attract advertising dollars. Hence, stations petition the FCC to allow them to identify themselves as being where their studio is, in the city, rather than where the transmitter/antenna is, often way out there. Again, a call to the station, or a look at the on-line database will answer this for you.
Listening from inside Certain Buildings Sometimes people can't get any AM reception in certain places, such as their workplace. I often hear this complaint. The building may be made of metal, use reinforced concrete walls (metal rods in the concrete to strengthen them) or have a metal roof. There may be computers or machines that cause interference, and hundreds of florescent lights in the ceiling. They may get no AM reception at all-- even on the huge 50,000 watt powerhouses. Unfortunately, there is not much one can do here. I always suggest putting the radio by a window, and the usual reply is that their desk or work-station is too far away from the window to do that, and they wouldn't be able to turn it up loud enough to hear it over the noise, or without disturbing their co-workers from that far away.
Answered By: thisisanswer - 6/5/2008