Did you ever wonder how a TV or radio signal gets programming from the broadcast station to your TV or radio set? It all starts with electricity. Radio and TV stations use alternating current or AC to create a signal that can travel from the studio's antenna to your set. AC is the same as the electric power in your home that is usually 120 volts. It is the type of electricity, which runs home appliances and lights the house. You may be familiar with one type of electrical power called DC, or direct current. DC is the type of electrical power you get from a battery and the current travels directly from positive to negative to form a circuit. AC is another type of electrical power usually generated by large generating stations and is transmitted to the user on power lines. It alternates from positive to negative 60 times or cycles per second that is measured as a frequency of 60 hertz.

As the frequency of alternating current gets higher than about 10,000 hertz (abbreviates Hz), the signal no longer wants to stay in the wires. If the length of the wire is right, the signal leaves the wire and goes through the air. So, at frequencies above 10,000 Hz or 10 Kilo-Hz, alternating current becomes "radio frequencies" or RF. Radio waves travel through space at the speed of light (about 300,000,000 meters per second). The distance a radio signal travels in one positive-to-negative cycle is called a wavelength.

Radio and TV engineers, electronics engineers, and amateur radio operators must know how to convert frequencies to wavelengths and vice-versa. This skill is needed to properly design the antennas that make broadcasting of signals possible. The equation used to do this conversion is:

l = (300) / f

Where:

l = The wavelength in meters (the symbol is the Greek letter lambda).

f = The frequency in MHz (or Megahertz or million hertz).

You are a radio operator. You are operating your radio equipment on 7,125 kHz (which is 7,125,000 Hz or 7.125 MHz). What is the wavelength in meters?

l = 300 / 7.125 = 42.1 meters (wavelength)

You are a radio operator, on 3,700 kHz, in what band are you operating?

Over 70 meters
Between 40 to 70 meters
Less than 40 meters