Magnetic Coupling Loop Antenna

Still another loop is shown in Fig. 16-4. This loop relies on magnetic coupling to perform the coupling of the transmitter. In this loop antenna, the coupling is via a small coupling loop and 50- coaxial cable to the transmitter. Capacitor C1 is used to resonate the loop, whereas capacitors C2 and C3 serve the purposes of loading and resonating the coupling loop. According to Mozzochi (1993), the voltages and currents with respect to the capacitors are

 

 The radiation patterns for the loop antenna are shown in Fig. 16-5. Note that four elevations are given (0°, 20°, 45°, and 60°). The bottom line is that small transmitting loop antennas are not very good for those who can afford to put up a better antenna, but for those whose tight quarters permit only a small transmitting loop, they are quite viable.