ASVAB (Armed Services Vocational Aptitude Battery)Electronics Information (EI)Medium
A technician is installing a new antenna system for a radio transmitter. To ensure maximum power transfer from the transmitter to the antenna, what characteristic of the transmission line should ideally match the impedance of both the transmitter output and the antenna input?
- ACharacteristic Impedance
- BResistance
- CInductance
- DCapacitance
Show answer & explanationAnswer & explanation
Correct answer: A. Characteristic Impedance
For maximum power transfer in RF systems, the characteristic impedance of the transmission line must be matched to both the source (transmitter) and the load (antenna). Mismatched impedances lead to reflections and power loss.
Why the other options are wrong
- B. Resistance is the opposition to current flow, and while it's a component of impedance, 'characteristic impedance' is the specific term for transmission lines.
- C. Inductance is a property of energy storage in a magnetic field, not the primary factor for power transfer matching.
- D. Capacitance is a property of energy storage in an electric field, not the primary factor for power transfer matching.
Characteristic Impedance
The impedance that a transmission line would have if it were infinitely long, crucial for efficient power transfer in RF systems.
- Measured in Ohms (Ω).
- Determined by the physical dimensions and materials of the line.
- Matching prevents reflections and minimizes power loss.
Memory trick: To Maximize Power, Match the Line's Z.