In a satellite system circular polarization is to be obtained. The antenna used is
Helical antenna produces a circularly polarized radiation if its two components are at right angles and are equal. It is very commonly used in radio telemetry.
A horizontal output stage is cutoff for retrace and 40% of trace. If time for each horizontal line is 64 μs and retrace time is 12 μs, the transistor is conducting for about
Total time for each horizontal line = .
Time for trace = 64 - 12 = 52 μs.
Time for which transistor is not conducting = 12 + 0.4 x 52 = 32.8 ms.
Time for which transistor is conducting = 64 - 32.8 = 31 μs.
A TV remote control works on the principle of
Infrared light is used in TV remote control.
As the magnitude of reverse bias is increased, the capacitance of varactor diode
When magnitude of reverse bias is increased, thickness of depletion layer increases.
Capacitance is inversely proportional to thickness.
To prevent overloading in the last IF amplifier one should use
Variable sensitivity prevents overloading.
Push pull amplifier is
It is a class B amplifier.
The tape recorders used in homes have
Common head and common amplifier is used.
In a communication system, noise is most likely to affect the signal
Noise is mostly generated in channel.
Each frequency in the modulating wave gives rise to four side bands.
Each frequency gives two side bands.
Assertion (A): CCIR-B system has 625 scanning lines per frame and 2 : 1 interlace.
Reason (R): The aspect ratio is 4 : 3
In VHS format each video head is tilted from azimuth by
Tilting of heads is done to reduce cross-talk.
The number of possible colours with a 4 line digital input monitor are
24 = 16.
Which of the following is a better recording medium?
Chromium di oxide has very good retentivity.
Convolution of x(t + 5) with impulse function δ(t - 7) is equal to
Convolution of | x(t + s) with d(t - 7)
x(t - 7 + 5) x(t - 2).
An angle modulated signal is given by s(t) = cos 2p (2 x 106t + 30 sin 150t + 40 cos 150t). The maximum frequency and phase deviations of s(t) are
s(t) = cos 2p(2 x 10+16t + 30 sin 150t + 40 cos 150t)
Phase deviation = 100 p
Frequency deviation = 7.5 kHz.
The PSD and the power of a signal g(t) are respectively Sg(ω) and Pg, the PSD and the power of signal a.g(t) are respectively
The simplest method of suppression of unwanted side band in AM is
Unwanted frequency is removed by filtering.
In a 100% amplitude modulated signal, the power in the upper sideband when carrier power is to be 100 W and modulation system SSBSC, is
Modulation index = 100% 1
Pc = 100 W
For attenuation of low frequencies we should use
Series capacitance has high reactance for low frequencies.
Assertion (A): A colour TV uses a SAW filter to give stable band pass response and high gain.
Reason (R): Devices using SAW principle are used in many systems.
SAW means Surface Acoustic Wave. SAW filter is very commonly used in TV sets.
At night the ionosphere can be considered to be consisting of
During night D layer is almost absent. Moreover F1 and F2 layers merge to form single F2 layer. Hence only D and F2 layers at night.
Which one of the following is true?
Z0 for twin wire cable is about 300 ohms while that for coaxial cable is about 75 ohms.
A balun transformer gives an impedance transformation of
Balun gives 4 : 1 impedance transformation and can be used to interconnect twin wire feeder cable to coaxial cable.
The EHT voltage in a picture tube of TV is
EHT voltage is 1 kV for each diagonal inch of CRT screen.
A 1000 kHz carrier wave modulated 40% at 40000 Hz is applied to a resonant circuit tuned to a carrier frequency and having Q = 140. What is the degree of modulator after transmission through the circuit?
m0 = m(1 + 4Q2δ2)1/2