Wireless Network Administration: Waves and Frequencies - dummies

# Wireless Network Administration: Waves and Frequencies

For starters, radio consists of electromagnetic waves that are sent through the atmosphere. You can’t see or hear them, but radio receivers can pick them up and convert them into sounds, images, or — in the case of wireless networks — data. Radio waves are actually cyclical waves of electronic energy that repeat at a particular rate, called the frequency.

The following illustration shows two frequencies of radio waves: The first is one cycle per second; the second is two cycles per second. (Real radio doesn’t operate at that low of a frequency, but one and two cycles per second are easier to draw than 680,000 cycles per second or 2.4 million cycles per second.)

The measure of a frequency is cycles per second, which indicates how many complete cycles the wave makes in one second (duh). In honor of Heinrich Hertz, who didn’t invent catsup, rather was the first person to successfully send and receive radio waves (it happened in the 1880s), cycles per second is usually referred to as Hertz, abbreviated Hz.

Thus, 1 Hz is one cycle per second. Incidentally, when the prefix K (for kilo, or 1,000), M (for mega, 1 million), or G (for giga, 1 billion) is added to the front of Hz, the H is still capitalized. Thus, 2.4 MHz is correct (not 2.4 Mhz).

The beauty of radio frequencies is that transmitters can be tuned to broadcast radio waves at a precise frequency. Likewise, receivers can be tuned to receive radio waves at a precise frequency, ignoring waves at other frequencies. That’s why you can tune the radio in your car to listen to dozens of different radio stations: Each station broadcasts at its own frequency.