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Small Antenna Design by Douglas B. Miron

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CHAPTER 3

Antenna Fundamentals II

3.1 Bandwidth and Quality Factor, Q

In the early days of electronic radio, the ability of a receiver to select just one station out of the many with sufficient strength to be detected was determined by the quality of a coil. Figure 3.1 shows a simplified schematic of an RF amplifier. To begin, we assume that the following stage has a very high input impedance so that the load on the active device (a vacuum tube in those days) is just the elements shown. Here rc is the resistance inherent in the coil wire. An ideal (perfect) coil would have no loss resistance. The voltage out of the stage is:

image

Figure 3.1 Simplified ...

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