• Home
  • Download PDF
  • Order CD-ROM
  • Order in Print
Methods of Feeding Energy to an Antenna
Figure 4-19.Groundscreen and counterpoise

Neets Module 10-Introduction to Wave Propagation, Transmission Lines, and Antennas
Page Navigation
  169    170    171    172    173  174  175    176    177    178    179  
4-22 Figure 4-17.—Mobile antennas. As stated above, a grounded quarter-wave antenna will resonate at the same frequency as an ungrounded half-wave antenna. This is because ground has high conductivity and acts as an electrical mirror image. This characteristic provides the missing half of the antenna, as shown in the bottom part of figure 4-18. In other words, the grounded quarter-wave antenna acts as if another quarter-wave were actually down in the earth. Figure 4-18.—Grounded quarter-wave antenna image. Characteristics of Quarter-Wave Antennas The grounded end of the quarter-wave antenna has a low input impedance and has low voltage and high current at the input end, as shown in figure 4-18. The ungrounded end has a high impedance, which causes high voltage and low current. The directional characteristics of a grounded quarter-wave antenna are the same as those of a half-wave antenna in free space. As explained earlier, ground losses affect radiation patterns and cause high signal losses for some frequencies. Such losses may be greatly reduced if a perfectly conducting ground is provided in the






Western Governors University

Privacy Statement
Press Release
Contact

© Copyright Integrated Publishing, Inc.. All Rights Reserved. Design by Strategico.