1. Mostly used radio receivers are?
a) pulsed receivers
b) CW receivers
c) TRF receivers
d) super heterodyne receivers
Explanation: Superheterodyne Receivers are radio receivers that use frequency mixing to convert a received high frequency signal to a fixed lower intermediate frequency which can be processed more conveniently. It is also the most used receivers. It is used in a variety of applications from broadcast receivers to two-way radio communication links as well as many mobile radio communications systems.
2. Find the step size of a signal with peak to peak amplitude of 4V and is quantized into 64 levels?
a) 32.3 x 10-3
b) 30.23 x 10-3
c) 62.5 x 10-3
d) 53.3 x 10-3
Explanation: Step size is the voltage difference between one digital level (i.e. 0001) and the next one (i.e. 0010 or 0000). Quantization step size is the smallest possible difference in amplitude.
Therefore, Step size,
3. If the step size of a system is 0.0625, find its quantization power?
a) 3.25 x 10-3
b) 3.25 x 10-4
c) 3.25 x 10-2
d) 3.25 x 10-1
Explanation: Quantization noise is a model of quantization error introduced by quantization in the analog-to-digital conversion (ADC) in telecommunication systems and signal processing. It is a rounding error between the analog input voltage to the ADC and the output digitized value.
4. Consider a wave, v = 15 sin (3πt + 5sin1300t), what is the carrier and signal frequency?
a) 2.5Hz and 200Hz
b) 1.5Hz and 100Hz
c) 1.5Hz and 207Hz
d) 5.5Hz and 500Hz
Explanation: Comparing with the general FM equation,
FM(t) = Ac sin(2πfct + βsin(2πfmt)),
Therefore,
Signal and Carrier frequency are respectively
5. SWR is 1 for ________
a) Open or Short Circuit
b) Open circuit only
c) Short circuit only
d) Series or Parallel Circuit
Explanation: Standing Wave Ratio (SWR) is defined as the ratio of the maximum radio-frequency (RF) voltage to the minimum RF voltage along the line. If the line is open or short circuited, SWR is always 1.
6. The resonance frequency of an amplifier is 7MHz and it is having a bandwidth of 10KHz. What is its Q factor?
a) 7000
b) 70
c) 700
d) 7
Explanation: Q factor = Frequency/Bandwidth
= 7MHz/10KHz = 700.
7. Which chart is used for calculations of transmission lines?
a) Andre chart
b) Smith chart
c) Wilson chart
d) Federer chart
Explanation:Smith chart is highly used in radio frequency engineering. Because it is highly useful in solving problems related with transmission lines and matching circuits. It is highly useful for displaying multiple parameters like impedance, admittance etc simultaneously.
8. What is the effective power if the transmitted power of 5W is increased to 50dB?
a) 100KW
b) 300KW
c) 500KW
d) 700KW
Explanation: According to given problem, 10log10 (P/Pt) = 50,
10log10 (P/5) = 50.
So, P = 500KW.
Where, P = Effective Power, Pt = Transmitted Power.
9. Field intensity follows ________
a) Bragg’s law
b) Inverse square law
c) Coulomb’s law
d) Gauss’s law
Explanation: Strength of an electric field due to a charge Q is inversely proportional to the square of the distance from the source. In electrostatics, inverse square law is also known as Coulomb’s Law.
10. If the power density at a given distance ‘R’ is one microwatt per square meter and the effective area of antenna is one square meter then the power captured by antenna is one microwatt.
a) True
b) False
Explanation: The above statement is true because power density is equal to
where,
Power Density = 1 mW
Pt = Power captured by antenna,
Area of antenna = 4πR2 = 1m2.