Subelement J: Antennas— Topic 64: Voltage, Current and Power Relationships
Question 3-64J6
Element 3 (GROL)There is an improper impedance match between a 30 watt transmitter and the antenna, with 5 watts reflected. How much power is actually radiated?
Explanation
When there is an impedance mismatch between a transmitter and an antenna, some of the power sent towards the antenna is reflected back towards the transmitter. The power that is actually radiated into space by the antenna is the difference between the forward power supplied by the transmitter and the reflected power.
In this scenario:
* Forward power from the transmitter = 30 watts
* Reflected power = 5 watts
Therefore, the power actually radiated is calculated as:
Radiated Power = Forward Power - Reflected Power
Radiated Power = 30 watts - 5 watts = 25 watts.
* **A) 35 watts** is incorrect because it adds the reflected power, which is not radiated.
* **B) 30 watts** is incorrect because it ignores the reflected power; not all power is radiated when there's a mismatch.
* **D) 20 watts** is an incorrect calculation.
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