ts reserved. Any use is subject to the Terms of Use as given at the website. Radio Engineering Concepts Radio Engineering Concepts television stations are in the very high frequency (VHF) band around 100 MHz. Air- craft radios operate in the VHF band as well. Electromagnetic radiation propagates at the speed of light c, which is about 3 X 1010 cm/s. Therefore, Advanced Mobile Phone Service (AMPS), the U.S. analog cellular system, at 900 MHz frequency, has a wavelength of about 33 cm, and the primary cdmaOne fre- quency, 1.9 GHz, has a wavelength of about 16 cm. Wavelength is a major element in determining the types of attentuation that we will need to manage. For example, in the upper microwave bands used for satellite transmission, wavelength is a fraction of a centimeter, and raindrops can cause attenuation. However, rain is not a problem for cellular systems. Attenuation tends to occur when the intervening objects are of a size about equal to one-half the transmission wavelength. 3 To put radio frequencies perspective, the visible red laser light used in fiber optic cable is around 500 THz, 500,000,000,000,000 cycles per second, with a wavelength of about 0.00006 cm. In a sound wave, there is some atmospheric pressure at every instant of time, SO we can say that the atmospheric pressure is a function of time, and we can describe that function as the time response of the sound wave. In our human experience, sound usu- ally comes in periodic waves, and the number of waves per unit time determines the pitch, the frequency of the sound. Normal sound is a mixture of many frequencies, and its frequency response is often more informative than its time response. 4 A radio wave has a voltage at every instant of time, SO its time response is voltage rather than air pressure. Radio also is usually transmitted in periodic waves with an associated frequency. As in the case of sound, radio waves usually contain many fre- quencies, and their frequency response is important. A function can be represented as f(x). In the case 