For all wave forms, the velocity, wavelength, and frequency are related so that the product of frequency and wavelength is equal to the velocity. For radiowaves, this relationship can be expressed Ln the following form:
A wavelength in meters (m ) F * frequency in hertz (Hz) e = dielectric constant of the propagation medium c « velocity of light (300,000,000 m/s).
The dielectric constant (e) is a property of the medium in which the wave propagates. The value of e is defined as 1,000 for a perfect vacuum and veiy nearly 1.0 for dry air (typically 1.006), In most practical applications, the value of e in dry air is taken to be 1.000. For media other than air or vacuum, however, the velocity of prop agation is slower add the value of e relative to a vacuum is higher. Teflon, for example, can be made with € values from about 2 to 11.
Equation (1-1) is more commonly expressed in the forms of Eqs, (1-2) and
Microwave letter bands
During World War II, the U.S. military began using microwaves in radar and other applications. For security reasons, alphabetic letter designations were adopted for each band in the microwave region. Because the letter designations became ingrained, they axe still used thrnughout industry and the defense establishment. Unfortunately, some confusion exists because there are at least three systems currently in use: pre-1970 military (T^ble 1-5), post-1970 military (Table l-f>), and the IEEE and industry standard (Table 1-7), Additional confusion is created because itie military and defense industry use both pre- aiui post-1970 designations simultaneously and industry often uses military rather than IEEE designations. The old military designations (Table 1-5} persist as a matter of habit .
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