1. The gain of antenna (G) is the ratio of power radiated in a particular direction to the power radiated from an isotropic antenna.
a) True
b) False
Explanation: Gain of antenna,
2. EM waves are attenuated as they travel.
a) True
b) False
Explanation: Electromagnetic radiation can travel through many forms of medium. They travel at the speed of light in air or free space, which are ideal media. However conductive media like metals form a barrier through which they do not travel. There are also some media through which when they travel, get attenuated. EM waves are attenuated as they travel because both field and power decrease as distance increases.
3. Envelope Detector is a/an ________
a) Coherent detector
b) Asynchronous Detector
c) Synchronous Detector
d) Product Demodulator
Explanation: An envelope detector is used to demodulate a previously modulated signal by removing all high frequency components of the signal. The capacitor and resistor form a low-pass filter to filter out the carrier frequency. Envelope detectors are asynchronous in nature. The advantage of asynchronous over synchronous is that it is simple, cheap and setup is faster.
4. Effective radiated power (ERP) is equal to ________
a) Pt×Gt×Pd
b) Pt×Pd
c) Gt×Pd
d) Pt×Gt
Explanation: Effective Radiated Power (ERP) measures the combination of the power emitted by the transmitter and the ability of the antenna to direct that power in a given direction. Thus, Effective Radiated Power is equal to the product of antenna gain (Gt) and power transmitted (Pt).
5. Power density from an isotropic antenna is equal to ________
a) \(\frac{P_t}{4 \pi R^2}\)
b) \(\frac{P_c}{4 \pi R^2}\)
c) \(\frac{P_t}{2 \pi R^2}\)
d) \(\frac{P_t}{4 \pi R}\)
Explanation: Power of a transmitter that is radiated from an isotropic antenna will have a uniform power density in all direction. An isotropic antenna is an ideal antenna that radiates its power uniformly in all directions. There is no actual physical isotropic antenna. However, an isotropic antenna is often used as a reference antenna for the antenna gain. The power density at any distance ‘R’ for an isotropic antenna is equal to \(\frac{P_t}{4 \pi R^2}\).
6. Compact discs mainly use ________
a) optical recording
b) magnetic recording
c) magnetic retrieval
d) both optical and magnetic recording
Explanation: Compact disk (CD) is mainly used for storage of data. It was developed only for store and play only audio but was later adapted for storage of data also. It mainly used optical recording and retrieval
7. If the distance between antenna and source doubles, the received signal power decreases by 1⁄4.
a) True
b) False
Explanation:It is due to the R2 term in formula,
. Thus, the received signal power is inversely proportional to the distance between antenna and source.
8. Power density follows inverse square law.
a) True
b) False
Explanation: From the given formula,
With increase in distance, power density decreases. So, we can also say that power density is inversely related to distance. Thus, Power density follows inverse square law.
9. There is no requirement of IF amplifier stages for a video monitor.
a) True
b) False
Explanation: IF amplifiers are used to change the frequency levels in circuits that are too selective, difficult to tune, and unstable. However, Video amplifier is used to amplify video signals before passing them to a Cathode ray tube. And there is no need of IF amplifier stages for a video monitor.
10. Helical antenna is circularly polarized.
a) True
b) False
Explanation: A helical antenna is an antenna consisting of one or more conducting wires (monofilar, bifilar, or quadrifilar with 1, 2, or 4 wires respectively) wound in the form of a helix. In helical antenna, polarization is equally divided between vertical and horizontal components and thus it is circularly polarized.