← MES Jr. Grade
Past Questions
For AM receivers the standard IF frequency is
A)
106 KHz
B)
455 KHz
C)
1.07 MHz
D)
10.7 MHz
In standard AM broadcast receivers, the intermediate frequency (IF) is conventionally 455 kHz. This value is widely used because it provides a good compromise between selectivity, image-frequency rejection, and ease of filter design. Option (d) 10.7 MHz is the standard IF for FM receivers, not AM. Option (c) 1.07 MHz is too high for standard AM IF, and (a) 106 kHz is not the usual standard.
The number of interrupt lines in 8085 microprocessor is
A)
3
B)
4
C)
5
D)
7
The 8085 microprocessor has 5 interrupt lines: TRAP, RST 7.5, RST 6.5, RST 5.5, and INTR. Hence the correct answer is 5. Options 3, 4, and 7 are incorrect because they do not match the standard interrupt structure of the 8085.
Satellite communication uses
A)
3 to 6 GHz
B)
3 to 10 MHz
C)
10 to 50 GHz
D)
100 to 200 GHz
Satellite communication commonly uses microwave frequencies, especially the C-band around 3.7 to 4.2 GHz for downlink and 5.925 to 6.425 GHz for uplink. Hence the general range given as 3 to 6 GHz is correct. The other options are not suitable: 3 to 10 MHz is far too low for satellite links, while 10 to 50 GHz and 100 to 200 GHz are much higher bands and not the standard basic range asked in such exam questions.
Which of the following parameters is negligible in transmission lines?
A)
R
B)
L
C)
C
D)
G
In transmission line modeling, the shunt conductance G represents leakage current through the insulation between conductors. For overhead transmission lines, this leakage is extremely small, so G is usually neglected. Resistance R, inductance L, and capacitance C are all significant and are included in line analysis.
Which of the following is taken as reference antenna for directive gain?
A)
½ wave dipole
B)
elementary doublet
C)
isotropic antenna
D)
infinitesimal dipole
Directive gain is defined with respect to a reference antenna that radiates equally in all directions, i.e., an isotropic antenna. Hence, the directive gain compares the radiation intensity of the given antenna to that of an isotropic radiator. A half-wave dipole is commonly used as a reference for gain in some contexts, but for directive gain the standard reference is the isotropic antenna. Therefore, option (c) is correct.
A 400 W carrier is modulated to a depth of 75 percent. The total power in modulated wave will be
A)
38.5 W
B)
400 W
C)
512.5 W
D)
615.5 W
For standard AM, total transmitted power is
P_t = P_c \left(1 + \frac{m^2}{2}\right),
where P_c is carrier power and m is modulation index.
Given:
P_c = 400 W, m = 75% = 0.75
So,
P_t = 400 \left(1 + \frac{0.75^2}{2}\right)
= 400 \left(1 + \frac{0.5625}{2}\right)
= 400 (1 + 0.28125)
= 400 \times 1.28125
= 512.5 W.
Hence, the correct answer is 512.5 W. The other options do not match the AM power formula.
A sinusoidal voltage of 2 kV peak value is amplitude modulated to give 20% modulation. The peak value of each side band term is
A)
800V
B)
400V
C)
200V
D)
100V
For single-tone AM, the peak value of each sideband component is (mVc)/2, where m is the modulation index and Vc is the carrier peak value. Here, Vc = 2 kV = 2000 V and m = 20% = 0.2. So each sideband peak = (0.2 × 2000)/2 = 200 V. Hence, the correct option is (c).
Show that TEM waves cannot propagate through a hollow waveguide.
What are TE and TM modes? Why is TE called the dominant mode in rectangular waveguide?
The beam of a radar should be
A)
Very narrow
B)
Very wide
C)
Neither too narrow nor too wide
D)
Either (b) or (c)
A radar beam should be very narrow so that it can focus energy in a specific direction, improve angular resolution, and accurately detect the target’s direction. A wide beam would spread energy over a larger area, reducing directionality and precision. Hence, the correct choice is (a) Very narrow.
What is quantization of signals? How can the quantization error be reduced?
The highest priority of interrupt in 8085 microprocessor system is
A)
RST 7.5
B)
RST 6.5
C)
INTR
D)
TRAP
In the 8085 microprocessor, TRAP has the highest interrupt priority. It is a non-maskable, vectored interrupt, so it cannot be disabled by the interrupt enable/disable instructions. The priority order is: TRAP > RST 7.5 > RST 6.5 > RST 5.5 > INTR. Hence, among the given options, TRAP is correct. INTR has the lowest priority among these interrupts.
Which principle of operation of cavity wave meters is used in microwave networks?
A)
phase shift
B)
resonance
C)
polarisation shift
D)
gyration
Cavity wave meters work on the principle of resonance. A cavity resonator is coupled to the microwave network, and when its resonant frequency matches the signal frequency, a strong response is observed. This makes it useful for measuring microwave frequency. The other options are not the operating principle of cavity wave meters: phase shift is related to transmission effects, polarisation shift is unrelated, and gyration refers to ferrite devices like gyrators/circulators.
The rate at which information can be carried through a communication channel depends on
A)
carrier frequency
B)
bandwidth
C)
transmission loss
D)
transmitted power
The information-carrying capacity of a communication channel is primarily determined by its bandwidth. According to Shannon’s channel capacity concept, a wider bandwidth allows more information to be transmitted per unit time. Carrier frequency does not directly decide capacity, while transmission loss and transmitted power affect signal quality and range, not the basic channel capacity in the same direct way as bandwidth.
If a line is terminated in characteristic impedance Z0; the input impedance measured at the input will be
A)
Z0
B)
Z0 /2
C)
zero
D)
infinite
For a transmission line terminated in its characteristic impedance Z0, there is no reflection at the load. Hence the input impedance seen at the sending end equals the characteristic impedance itself, i.e., Z_in = Z0. Therefore, the correct option is (a). The other options are incorrect because Z0/2, zero, and infinite input impedance occur only under special mismatched or open/short-circuited conditions, not when the line is properly matched.
The characteristic impedance of a cable is about
A)
2 Ω
B)
5 Ω
C)
50 Ω
D)
300 Ω
The characteristic impedance of a cable is typically around 50 Ω for standard transmission/coaxial cables. This is a widely used nominal value in electrical and communication engineering. 2 Ω and 5 Ω are far too low, while 300 Ω is more typical of certain twin-lead transmission lines, not the usual cable characteristic impedance asked here.
The velocity of sound waves in air
A)
is constant at all temperatures
B)
varies directly as temperature
C)
varies inversely as absolute temperature
D)
varies directly as square root of absolute temperature
The speed of sound in air is given by v = \u221a(\u03b3RT/M), so it is proportional to the square root of the absolute temperature (in Kelvin). Hence, as temperature increases, sound velocity increases as \u221aT. Option (a) is wrong because velocity changes with temperature, (b) is wrong because it is not directly proportional to T, and (c) is wrong because it does not vary inversely with temperature.
In the 8085 microprocessor the RST6 instruction transfers the program execution to the following locations
A)
30H
B)
24H
C)
48H
D)
60H
In the 8085 microprocessor, the RST instructions are restart instructions that transfer control to fixed memory locations. The vector address is calculated as 8 times the RST number. For RST 6, the address is 6 × 8 = 48H. Hence, execution jumps to 48H. The other options correspond to different RST vectors: RST 3 = 18H, RST 4 = 20H, RST 5 = 28H, and RST 7 = 38H.
The number of pins in microprocessor 8086 is
A)
30
B)
40
C)
50
D)
60
The Intel 8086 microprocessor is a 16-bit microprocessor packaged in a 40-pin DIP (Dual In-line Package). Therefore, the number of pins is 40. The other options are incorrect because 30, 50, and 60 are not the standard pin count of the 8086.
An audio signal of FM radio station is sampled at a rate of 15% above the Nyquist rate. Signal is sampled in 512 levels and bandwidth of the signal is 4 KHz. What will be the minimum bandwidth required to transmit this signal?
Describe the flag registers in 8085 microprocessor.
In a klystron amplifier the force on all electrons
A)
Causes acceleration of all electrons
B)
Causes retardation of all electrons
C)
Causes acceleration of some electrons and retardation of others
D)
None of the above
In a klystron amplifier, the RF field in the buncher cavity interacts with the electron beam and produces velocity modulation. Depending on the phase of the RF field at the instant an electron passes through, some electrons are accelerated while others are retarded. This creates electron bunching, which is essential for amplification. Hence, the force does not act the same way on all electrons.
Light may be propagated along a fiber-optic cable in which of the following modes?
A)
multimode step index
B)
single-mode step index
C)
multimode graded index
D)
all of these
Light can propagate through fiber-optic cables in multiple modes depending on the fiber design: multimode step-index, single-mode step-index, and multimode graded-index. Since all three are valid propagation modes, the correct answer is 'all of these'.
In a PCM system, if we increase the quantization levels from 2 to 8, how do the relative bandwidth requirements vary?
A)
Get doubled
B)
Get tripled
C)
Remain same
D)
Become eight times
In PCM, the number of bits per sample is n = log2(L), where L is the number of quantization levels. Increasing levels from 2 to 8 changes n from 1 bit to 3 bits. Since PCM bit rate and hence required bandwidth are proportional to the number of bits per sample, the bandwidth becomes 3 times. Therefore, the relative bandwidth requirement gets tripled. Options (a), (c), and (d) are incorrect because the increase is not by a factor of 2, unchanged, or 8 in this case.
What is a Magic Tee? Obtain its Scattering matrix.