WorksheetsCOGNITIONIS#2
Total questions: 20
Worksheet time: 10mins
Why do coaxial (coax) cables specify a minimum bend radius?
Too tight of a bend alters the internal physical dimension to where the impedance change profoundly affects the internal signal.
To prevent breakage.
The outer insulation might split if the bend is too tight.
Coaxial cables do not have a minimum bend radius.
At what rate does the power of an RF signal attenuate in free space?
2 dB for every doubling of distance.
4 dB for every doubling of distance.
6 dB for every doubling of distance.
8 dB for every doubling of distance
What does the "S" in S-Parameters stand for?
Splattering
Scintillation.
Stability.
Scattering.
How does an antenna achieve gain when it has no active signal amplification?
Excess electrons within the antenna structure increase the signal power.
Gain is achieved by directing (concentrating) a majority of the signal in a preferred direction rather than equally in all direction.
By varying the diameter of the radiating elements.
Antennas do not provide any sort of gain.
What is the phase shift at the shorted end of a coaxial cable?
0°
90°
180°
360°
Which of the following are the effects/ makes use of eddy current?
Skin effect
Electromagnetic brake
Induction cooker
All of the above
For good conductors E and H are:
In time phase with each other
Out of phase by 90°
Out of phase by 45°
Out of phase by 180°
If D, G, ƞ denote directivity, power gain and efficiency of an antenna respectively, then:
DGƞ=1
ƞ=DG
D=ƞG
D= G/ƞ
The inconsistency of Ampere’s was corrected by Maxwell and the term added was:
Charge density
Surface current density
Displacement current
Magnetic current
When a particular mode was excited in a waveguide, there appears an extra magnetic field component, in the direction of propagation. The resulting mode is:
Transverse magnetic
Transverse electric
Longitudinal
Transverse electromagnetic
A range of microwave frequencies more easily passed by the atmosphere than are the others is called a:
Window
Critical frequency
Gyro frequency range
Resonance in the atmosphere
Ionospheric preparation is not possible for microwaves because:
Microwaves will be fully absorbed by the ionospheric layers
There will be an abrupt scattering in all directions
Microwave will penetrate through the ionospheric layers
There will be dispersion of microwave energy
Which of the following can be used for amplification of microwave energy?
Travelling wave tube
Magnetron
Reflex Klystron
Gunn diode
What do you call an attenuation that occurs over many different wavelengths of the carrier?
Rayleigh fading
Rician fading
Wavelength fading
Slow fading
The selectivity of most receivers is determined largely by:
Sensitivity
Characteristics of IF section
Antenna direction
All of the above
A superheterodyne receiver with an IF of 450 kHz is tuned to a signal at 1200 kHz. The image frequency is:
750 kHz
990 kHz
1650 kHz
2100 kHz
In a broadcast superheterodyne receiver having no RF amplifier, the loaded Q of the antenna coupling circuit is 100. If the intermediate frequency is 455 kHz, the rejection ratio at 25 MHz will be
1.116
1.386
2.116
2.386
FM amplifier in a superheterodyne receiver:
Increases selectivity
Suppresses noise
Provides improved tracking
Improves the rejection of the image frequency
Padders are used in a receiver to:
Discard the carrier
Facilitate tracking
Filter the input signal
Suppress noise
As compared to tuned radio frequency receivers, which of the following is the advantage of using superheterodyne receivers?
High gain and better sensitivity
Better selectivity at high frequencies
Stability
Noise suppression
