Question
What transformer turns ratio matches an antenna’s 600-ohm feed point impedance to a 50-ohm coaxial cable?
Answer Options
- A) 3.5 to 1
- B) 12 to 1
- C) 24 to 1
- D) 144 to 1
Correct Answer: A
Explanation
The impedance ratio of a transformer is equal to the square of the turns ratio: Z_1/Z_2 = (N_1/N_2)^2. We need to find the turns ratio N_1/N_2 = \sqrt{Z_1/Z_2}. The ratio required is 600 \text{ ohms} to 50 \text{ ohms}.
The required turns ratio (N) is: N = \sqrt{\frac{Z_1}{Z_2}} = \sqrt{\frac{600 \text{ }\Omega}{50 \text{ }\Omega}} = \sqrt{12} \approx 3.464 \text{ to } 1. Rounding to the nearest choice, the required turns ratio is 3.5 \text{ to } 1. (Note that 12:1 is the impedance ratio, not the turns ratio).
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