Reply To: Radio Q&A

  • Farm-Ranch-Homestead

    March 1, 2024 at 7:38 pm

    What do frequency, bandwidth, and wavelength have to do with radio?

    All radio systems operate at specified frequencies (cycles per second), otherwise they wouldn’t work well. For instance, when you tune your car radio to 97.7 on the “FM dial,” you are tuning your car radio to receive at 97.7 MHz. In the posts about radio “spectrum,” I discussed some of these frequencies and what they’re used for. The FCC regulates the use of radio frequencies, and assigns different frequencies for different uses. Refer to the posts about radio spectrum to learn which frequencies can be used for civilian purposes.

    “Bandwidth” is the measure of how “wide” a radio signal is. Although a radio may be tuned to a specific frequency, the actual signal covers a small range of frequencies, centered on the tuned frequency. Think of it in terms of a traffic lane. The tuned frequency would be the center of the lane, but a car traveling in the lane is wider than the centerline. Radio signals are similar, and the allowed bandwidth varies with different radio services. The FCC regulates the limits to bandwidth.

    Wavelength is the length of one cycle of the radio signal. Wavelength is measured in either meters or centimeters for most civilian radio applications. Different bands, especially the Amateur radio bands, are referred to in terms of wavelength, such as the “80 meter,” “10 meter,” or “70 centimeter” bands. Wavelength has an inverse relationship to frequency, so you can determine the approximate frequency from the wavelength, and vice-versa. Wavelength (in meters) multiplied by frequency (in MHz) equals a constant of 300. 300/frequency (in MHz) = wavelength (in meters) and 300/wavelength (in meters) = frequency (in MHz). Thus, for example, the frequency of the 10 meter band can be calculated as approximately 30 MHz [300/10(m) = 30(MHz)].