AM stands for Amplitude Modulation. This technique involves injecting the audio signal into the RF carrier in such a manner that the power level or amplitude of the transmitter swings in direct proportion to the waveform of the audio. The frequency of the carrier remains relatively constant.

AM radio came before FM. Over the years, FM became the broadcast choice for music because of its superior high-fidelity whereas AM has become relegated to mostly talk-radio shows, both English & foreign-speaking.
 

It is not possible to purchase a “better” antenna for the transmitter. The antenna that comes with the unit is the perfect antenna for this transmitter. The antenna is probably the single most important component of any transmitter, big or small. And it's well worth understanding how the antenna works on your transmitter, so you'll understand how to get the best reception possible.

4. Q. What should I know about antenna placement?

The transmitter and its antenna can be placed anywhere in the house, but will work best if placed on a front wall or window, facing the broadcast area. If possible, placing the unit & antenna on the second story (but not any higher).  Second story placement will give you the best results.

Mount the antenna VERTICALLY using push pins.  Do not spread-out the antenna along a baseboard.

Don't install the Transmitter near a florescent light, a refrigerator, a cathode tube television or computer monitor, washer/dryer, as A/C motors and transformers emit radiant frequencies which play havoc with your FM broadcast.

Set up your antenna FIRST before turning on the unit's power, and turn-off the unit's power before disconnecting the antenna.

Strive for uninterrupted lines of sight.  Commercial FM radio falls in the VHF band where line-of-sight suggests the maximum range of signal converge. Licensed FM radio stations combine powerful transmitters with antennas placed on towers and buildings, high above the average terrain, and so in fact slightly surpass this line of sight limitation. Often several antennas are placed along one tower and fed by a single transmitter so as to maintain optimum signal density close to the ground. The understanding here is that a signal that can be detected 100 miles away is of little use if it cannot be detected easily by the average listener at ground level.

A micro transmitter has insufficient power to reach the line of sight potential provided by an antenna placed high above the ground. Long coaxial feed lines eat up power as well. Typically a micro transmitter works best with an antenna less than 50 feet above the terrain since this will provide an optimum balance between ground level signal density and range. Ideally the feed line should be kept under 50 feet and the antenna kept away from nearby obstructions.  Business Ad Radio's antenna are only 84 inches long...easily set-up and concealed in most all indoor applications.

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Commercial AM radio falls in the Medium Wave band where wavelengths of several hundred meters appear. Ground level signals of this nature tend to bend around the earth while skyward bound energy is absorbed or deflected by the ionosphere. Licensed AM radio stations use towers that are electrically insulated at the bottom from the earth so the entire tower in effect becomes the broadcast antenna.

Low power transmitters in this range of the radio spectrum benefit from antennas that are long and vertical which start close to the ground, however the rules mandate that the feed line and antenna may not exceed 10 feet in length.

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