Question
What is the approximate feed point impedance at the center of a two-wire half-wave folded dipole antenna?
Answer Options
- A) 300 ohms
- B) 72 ohms
- C) 50 ohms
- D) 450 ohms
Correct Answer: A
Explanation
A folded dipole is a standard half-wave dipole element that has a second conductor connected in parallel at the ends, forming a thin loop. This secondary conductor affects the current distribution on the antenna, which has a direct and predictable effect on the feed point impedance.
The approximate feed point impedance at the center of a two-wire half-wave folded dipole is 300 \text{ ohms}. This impedance is approximately four times the impedance of a simple half-wave dipole (which is about 72 \Omega in free space). This 300 \Omega impedance is ideal for direct connection to 300 \Omega TV twinlead or for use with a 4:1 balun to match a 75 \Omega or 50 \Omega coaxial feed line.
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