Long Distance Radio Transmission

The wide bandwidth of FM radio allows it to be transmitted within the Very High Frequency radio spectrum. The range for the Very High Frequency radio wave spectrum typically falls between 50 and 200 miles. The VHF wavelengths that operate and travel similar to light can have very long distances when reflected from the ionosphere. The long distance transmission typically is appealing for dense structures or location landlocked within areas with high elevation, like hills or mountains. Typically, 100,000 watt FM radio stations can travel a distance of 100 to 150 miles without any interfering signals.

FM in VHF
Finding the longest distance radio transmission can be extremely effective for businesses and individuals looking for clear radio reception that can overcome some of the aforementioned obstacles. Because the VHF frequencies usually travel in straight lines like light, the distance traveled by the signals does not always depend on the level of wattage power. Often times, the number of competing signals in nearby proximity can be a greater determinant of the strength of the radio transmission under consideration. Before the increase in competing radio signals, some of the FM stations that ran over 300,000 watts recorded 300 miles as their longest distance radio transmission.

FM, AM or Shortwave Radios?
Back in 1920, one of the first public FM radio broadcasts for entertainment eventually recorded its longest distance radio transmission at 1,000 miles. When this CBS station initially began its transmission, the distance was recorded at 100 miles. The reason that so many commercial industries like aviation use AM station is so they do not have to compete with the excessive number of FM signals competing for reception around the world. Most AM stations in North America have a broadcast power limit of around 50,000 watts. In 1924, several amateur radio operators were able to use shortwave radios to transmit signals across the ocean for a distance of around 6,000 miles.

Long Distance Shortwave Radios
Shortwave radios utilize the medium and high frequency sectors of the radio spectrum. Shortwave radios reflect off the ionosphere like FM signals, and typically have the largest skip distance zones amongst all radios. Shortwave radios can transmit signals to virtually any location on the earth. Shortwave radios are often used for long-distance communications with aircrafts and ships.

These radios are also an ideal choice for reaching location that lack radio service or wired communications. Other uses for long-distance short wave radios include broadcasting music and voice, emergency signals and education transmission as well. The shortwave radios are typically a favored choice for radio enthusiast because of their ability to transmit signals to nearly any location, regardless of the distance. It’s important to remember that the condition of the ionosphere and velocity of propogation typically depend heavily on the current activity of sunspot cycles.