Directional High Frequency Antenna: Directional High Frequency Antenna are likely to differ from lower-frequency ones for two reasons. These are the HF transmission/reception requirements and the ability to meet them. Since much of HF communication…
Antenna Coupling: Antenna Coupling : Low and medium frequency antennas are the ones least likely to be of resonant effective height and are therefore the least likely to have purely resistive input impedances. This precludes…
Effects of Antenna Height: At low and medium frequencies, where wavelengths are long, it often becomes impracticable to use an antenna of resonant length. The vertical antennas used at those frequencies are too short electrically.…
Effects of Ground on Antenna Performance: The Effects of Ground on Antenna Performance on a detailed discussion of the interaction (see Figure 9-11). Ungrounded Antennas: As was know, when a radiation source is placed near a…
Radiation Pattern of Antenna: The important terms and definitions used in connection with antennas and their Radiation Pattern of Antenna are Antenna Gain and Effective Radiated Power: Certain types of antennas focus their Radiation Pattern…
Antenna Characteristics: The following Antenna Characteristics isolated from surfaces which will alter or change their radiation patterns and efficiency. Current and Voltage Distribution: When an RF signal voltage is applied at some point on an…
Antenna Definition: The Antenna Definition is a quick review of impedance matching (basic transformer theory) and resonant circuits. It was pointed out that maximum power transfer could be achieved only when the source matched the…
Extraterrestrial Communications: Extraterrestrial Communications : The most recent, and by far the fastest-growing, field of communications involves the use of various satellite relays, of which the first was launched in 1957,-12 years after the practicability…
Tropospheric Scatter Propagation: Tropospheric Scatter Propagation is a means of beyond-the-horizon propagation for UHF signals. Tropospheric Scatter Propagation uses certain properties of the troposphere, the nearest portion of the atmosphere (within about 15 km of…
Space Waves: Space waves generally behave with merciful simplicity. They travel in (more or less) straight lines! However, since they depend on line-of-sight conditions, space waves are limited in their propagation by the curvature of…
