Question
Which of the following describes a Zepp antenna?
Answer Options
- A) A horizontal array capable of quickly changing the direction of maximum radiation by changing phasing lines
- B) An end-fed half-wavelength dipole
- C) An omni-directional antenna commonly used for satellite communications
- D) A vertical array capable of quickly changing the direction of maximum radiation by changing phasing lines
Correct Answer: B
Explanation
The Zepp antenna (short for Zeppelin) originated from its use on early airships, where it was fed from the control cabin at one end. This antenna is a variant of the half-wave dipole, distinguished by its unique feed point placement.
The Zepp antenna is described as an end-fed half-wavelength dipole. Unlike a center-fed dipole which has a low feed point impedance, the end of a half-wave wire is a high-voltage, low-current point, resulting in a very high feed point impedance (thousands of ohms). It is typically fed through a parallel-wire matching section to transform this high impedance down to a value manageable by coaxial cable or an antenna tuner.
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