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
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
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
You are a radio operator, on 3,700 kHz, in
what band are you operating?
Between 40 to 70 meters
than 40 meters