# Antenna Measurements Questions and Answers – Measurement of Gain

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This set of Antennas Multiple Choice Questions & Answers (MCQs) focuses on “Measurement of Gain”.

1. In which of the following type of measurement prior gain knowledge of antennas used in measurements is not necessary?
a) Absolute gain
b) Gain transfer method
c) Gain compromise method
d) Both gain transfer and absolute gain method

Explanation: In absolute gain method, the prior knowledge of gain of antennas used in the measurements is not necessary. Gain transfer or Gain compromise method requires the standard gains of the antennas used for measurements to compare the AUT.

2. Friss transfer formula is given by _____
a) $$P_r = P_t G_r G_t (\frac{λ}{4πR})^2$$
b) $$P_r = P_t G_r G_t (\frac{λ}{4πR})$$
c) $$P_r = \frac{P_t G_r G_t}{\frac{λ}{4πR}}$$
d) $$P_r = P_t G_r G_t (\frac{λ}{4πR^2})$$

Explanation: Friss transmission is basis for the absolute gain measurement. The Friss transfer equation is given by $$P_r = P_t G_r G_t (\frac{λ}{4πR})^2 \,where\, G_r,G_t$$ are the gains of receiving and transmitting antenna respectively.

3. Friss equation provided the basis for the absolute gain measurement.
a) True
b) False

Explanation: Friss transmission is the method used for the absolute gain measurement. The Friss transfer formula is given by $$P_r= P_t G_r G_t (\frac{λ}{4πR})^2 \,where\, G_r,G_t$$ are the gains of receiving and transmitting antenna respectively.

4. Which of the following is used mostly for the calibration of standard gain of antenna?
a) Absolute gain
b) Gain transfer method
c) Gain compromise method
d) Both gain transfer and absolute gain method

Explanation: In absolute gain method, the prior knowledge of gain of antennas used in the measurements is not necessary and it is used for standard gain calibration. Gain transfer or Gain compromise method requires the standard gains of the antennas used for measurements to compare the AUT.

5. In which of the following method does not require standard gain of antennas for gain measurements to compare AUT?
a) Absolute gain
b) Gain transfer method
c) Gain compromise method
d) Both gain transfer and absolute gain method

Explanation: Gain transfer and gain compromise methods require the standard gain calibration of antennas for gain measurements to compare the antennas under test. In Absolute gain method, gain of the antennas which are to be compared are known priory and this is used for the standard gain calibration

6. Antenna efficiency of a lossless isotropic antenna is dB is ____
a) 0
b) 1
c) 3
d) -3

Explanation: For a lossless antenna the whole peak power is radiated towards the receiver without any losses. So the antenna efficiency will be 100% so it is 0dB.

7. Relation between Antenna gain G and directivity D is ______
a) G = ∈r D
b) G = ∈r/D
c) G = D/∈r
d) G = 1/∈rD

Explanation: Antenna gain refers to the amount of radiation intensity in the desired direction to that of would have radiated when the isotropic antenna radiates. The relation between Antenna gain and Directivity is G = ∈r D, ∈r is the antenna efficiency.

8. What is the antenna efficiency if the gain equals to the directivity of the antenna?
a) 1
b) 0
c) 3
d) 2

Explanation: The relation between Antenna gain and Directivity is G=∈r D, ∈r is the antenna efficiency.
⇨ ∈r= $$\frac{G}{D}=1$$

9. Which of the following method is employed for the gain transfer method for antenna outdoor range?
a) Anechoic chamber
b) Tampered chamber
c) Reflection range
d) Compact range

Explanation: Free space or elevation or Reflection range can be employed for the gain transfer method. Anechoic, tampered chambers and compact ranges come under indoor ranges. In gain transfer method the unknown gain antennas are compared with the standard gain antennas.

10. Which of the following equation holds good for gain transfer method?
a) Gtest antenna = Gstd antenna) + $$10log⁡(\frac{P_{Test}}{P_{Std}})$$
b) Gtest antenna = Gstd antenna) – $$10log⁡(\frac{P_{Test}}{P_{Std}})$$
c) Gtest antenna + Gstd antenna) = $$10log⁡(\frac{P_{Test}}{P_{Std}})$$
d) Gtest antenna / Gstd antenna) = $$10log⁡(\frac{P_{Test}}{P_{Std}})$$

Explanation: In gain transfer method the unknown gain antennas are compared with the standard gain antennas. The relation between gains of test and standard antenna to the powers received by them are given by the equation
Gtest antenna = Gstd antenna) + $$10log⁡(\frac{P_{Test}}{P_{Std}}).$$

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