An antenna simply hanging up in free space isn’t worth much; we need to get our energy from the transmitter up to the antenna. Of course, we can bend down one end of the an- tenna and bring it into the house—but, except for certain special types, this is not the best idea for several reasons. Some
energy may be wasted because of absorption by nearby objects. Also, the normal radiation pattern of the antenna may be some- what upset.
For these reasons, in most cases, some type of feeder line is used to get the energy from the transmitter to the antenna as Figure. At this point we need to consider another matter: the impedance of the antenna at the point where the feeder must connect. Fortunately, the theoretical input impedance of a half-wave antenna fed in the center is a value which can be matched by a feedline which, in turn, is of a handy impedance value for powering from the common ham transmitter. Such an arrangement is the basis of the first antenna we will consider.
For these reasons, in most cases, some type of feeder line is used to get the energy from the transmitter to the antenna as Figure. At this point we need to consider another matter: the impedance of the antenna at the point where the feeder must connect. Fortunately, the theoretical input impedance of a half-wave antenna fed in the center is a value which can be matched by a feedline which, in turn, is of a handy impedance value for powering from the common ham transmitter. Such an arrangement is the basis of the first antenna we will consider.
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