Many other sources produce radio waves, including the sun, lightning, and power lines. If the frequency of these other waves overlap with the intended channel, the AM receiver can pick them up as changes in amplitude, resulting in noise or static.

Nevertheless, AM radio has been in decline for years, with many AM stations going out of business each year. Now there are only 4,684 left as of the end of 2015. AM is dying for a lack of listeners. Only 10 to 20 % of all radio listeners listen to it, and that depends upon the locale.

A radio or TV station cannot simply be turned off by the owner. They have to get the permission of the FCC and this is often difficult. So many AM stations remain on because of this. One reason AM broadcast is still around it is used mostly for talk radio.

Most AM radio stations are required by the FCC’s rules to reduce their power or cease operating at night in order to avoid interference to other AM stations. However, during nighttime hours the AM signals can travel over hundreds of miles by reflection from the ionosphere, a phenomenon called “skywave” propagation.

In AM broadcasts, sound signals are encoded by changing the amplitude, or maximum height, of radio waves. AM broadcasts use longer wavelength radio waves than FM broadcasts. Because of their longer wavelengths, AM waves reflect off a layer of the upper atmosphere called the ionosphere.

FM uses a higher frequency range and a bigger bandwidth than AM. Each FM station is allocated 150 kHz of bandwidth, which is 15 times that of an AM station. This means that an FM station can transmit 15 times as much information as an AM station and explains why music sounds so much better on FM.

Car, Boat, & Other Radios (Mobile & Fixed-Mount)

50,000 watts

For a broadcast of 6 watts, the transmission range will be 3 miles. At 15 watts, the range increases to 5 miles, at 40 watts to 10 miles and at 100 watts to 15 miles. The general rule of thumb is it will take four times the power to double the transmission distance.

How much power is 50,000 watts?…Convert 50,000 Watts to Horsepower.

HD Radio

A class station. A class stations are normally provided on double-line sections. At such stations a ‘line clear’ signal cannot be granted at the rear of a station unless the line on which a train is to be received is clear and the facing points set and locked. No shunting can be done after line clear has been granted.

Advantages of FM over AM All the transmitted power in FM is useful, while in AM most of the transmitted power is in carrier which contains no information. The amplitude of FM is constant which makes it independent of the modulation deption, while in AM modulation depth directs the transmitted power.

Disadvantages of FM: Much more Bandwidth (as much as 20 times as much)….Frequency Modulation

• Improved signal to noise ratio (about 25dB) w.r.t. to man made interference.
• Smaller geographical interference between neighboring stations.
• Less radiated power.
• Well defined service areas for given transmitter power.

AM broadcasting is radio broadcasting using amplitude modulation (AM) transmissions. It was the first method developed for making audio radio transmissions, and is still used worldwide, primarily for medium wave (also known as “AM band”) transmissions, but also on the longwave and shortwave radio bands.

XERA

For a variety of technical reasons, comparing lower (mid range 433MHz) and higher frequency 2.4GHz) compares like this: The lower frequency signals travel further than because the energy is higher and more concentrated in a single steady fashion that isn’t absorbed as easily by air, which consists of a good deal of …

Line of sight (LoS) is a type of propagation that can transmit and receive data only where transmit and receive stations are in view of each other without any sort of an obstacle between them. FM radio, microwave and satellite transmission are examples of line-of-sight communication.