Objective question

1. SHORT ANSWER QUESTIONS (ANTENNAS AND WAVE PROPAGATION)
SECTION – A
GENERAL
1 The first antenna was built by:
(a) J. D. Kraus (b) Guglielmo Marconi (c) Heinrich Hertz (d) R. J. Marhefka
2 The regular transatlantic message service started in:
(a) 1899 (b) 1900 (c) 1901 (d) 1902
3 Broadcasting began and the word radio was introduced in about:
(a) 1901 (b) 1910 (c) 1920 (d) 1930
4 If L, M, t, I, T and i represent Length, mass, time, electric current, temperature and
luminous intensity respectively the fundamental dimensions include:
(a) L, M and t only (b) L, M, t and I only
(c) L, M, t, I and T only (d) All L, M, t, I, T and i
5 The unit of electric flux density is:
(a) Coulombs per cubic meter (b) Coulombs per square meter
(c) Coulombs per meter (d) Coulombs
6 The wavelength of 2-GHz wave is:
(a) 15 cm (b) 15 mm (c) 1.5 cm (d) 1.5 mm
7 The relevant human dimension in terms of frequency is:
(a) KHz (b) Hundreds of KHz (c) MHz (d) Hundreds of MHz
8 The vector magnetic potential can be defined where:
(a) charge density is zero (b) current density is zero
(c) flux density is zero (d) for all time variant fields
9 The relation E = -V is not adequate for time varying fields and need to be modified to the
form E = - V + N, where N equals;
(a) – v / t (b) – A / t (c) – 2
v/ t2
(d) – 2
A/ t2
10 The inadequacy of the relation E = -V is realized on the application of the curl operation
to each side, since curl of the gradient is identically zero. But, from Faraday's’ Law E is
not generally zero. To effect an improvement the equation is modified to E =
(a) -V - D/t (b) -V - /t (c) -V - B/t (d) -V - A/t
11 Let the axial ratio (AR) of a polarization ellipse is defined in terms of the ratio of electric
field intensity E. If E2 is the value of E along major axis and E1 along minor axes AR = E2/E1.
Circular polarization is an extreme case of elliptic polarization which corresponds to:
(a) E1 = E2 and AR = 1 (b) E1 = 0 and AR = 1
(c) E1 = E2 and AR =  (d) E1 = 0 and AR = 

2. 12 Let the axial ratio (AR) of a polarization ellipse is defined in terms of the ratio of electric
field intensity E. If E2 is the value of E along major axis and E1 along minor axes AR = E2/E1.
Linear polarization is an extreme case of elliptic polarization which corresponds to:
(a) E1 = E2 and AR = 1 (b) E1 = 0 and AR = 1
(c) E1 = E2 and AR =  (d) E1 = 0 and AR = 
13 The polarization loss factor F for perfect match is:
(a) 1 (b) 10 (c)  (d) 0
14 The polarization loss factor F for total mismatch is:
(a) 1 (b) 10 (c)  (d) 0
15 If in a network Si is the input signal Ni is the input noise, So is the output signal and No is
the output noise the noise figure is given by:
(a) Si/So (b) Si+Ni / So+No (c) So/Si (d) So+No / Si+Ni
16 In general cosmic noise decreases with the increase in frequency and is of considerable
importance in:
(a) LF and MF bands (b) MF and HF bands
(c) HF and lower VHF bands (d) VHF and lower UHF bands.
17 The brightness “B” is related to the brightness temperature TB by the Rayleigh-Jeans
formula given by:
(a) B = (2 k TB) / 2
(b) B = 2
/ (2 k TB)
(c) B =  / (2 k TB) (d) B = (2 k TB) / 
18 Which of the following represents one of the Maxwell’s equations in correct form?
(a)  E  dl = - [B/ t]  dv (b) § H  dl = I + § [D/ t]  ds
(c) § D  ds =  dv (d)  B  ds = J dv OR = 0
19 If ES is the field intensity vector identified as a phasor by its subscript s, and k0 is the
wave number, the equation 2
ES = - k0
2
ES is called:
(a) Poisson’s equation (b) Coulomb’s gauge condition
(c) Vector Helmholtz equation (d) Diffusion equation
20 Identify the correct equation:
(a) A = -  2
v/ t2
(b) A = -  v/ t
(c) V = -  +  2
v/ t2
(d) V = - E – A2
/ t2
21. The Lorentz gauge condition is given by A =:
(a) -2
V/t2
(b) -V/t (c) -V (d) 0
22. The Coulombs gauge condition is given by A =:
(a) -2
V/t2
(b) -V/t (c) -V (d) 0
23. The free space wave number k0 is equal to:
(a) 0(00) (b) 0/(00) (c) 0(0/0) (d) 0/(0/0)

3. 24 If E is a function of  & t and has only Er component B will have
(a) Only Br component (b) only B component
(c) only B component (d) B & B components
25 The induction and radiation fields of an oscillating electric dipole become approximately
equal at a distance r, where r =:
(a) /6 (b) /4 (c) /3 (d) /2
26 An antenna can be assumed to have sinusoidal current distribution provided its length is:
(a)  /10 (b)  /5 (c)  /2 (d)  
27 If the radiated power of a quarter wave mono-pole is given by (1/2 )  0.609  Im2
(eff) /
2 the radiation resistance (in Ohms) of a half wave dipole is obtained to be:
(a) 36.5 (b) 18.25 (c) 73 (d) 146
28 A dipole antenna is a straight radiator, usually fed in the center. It produces a maximum
of radiation:
(a) in the plane parallel to its axis (b) in the plane normal to its axis
(c) at the place of feed (d) at its extreme ends
29. The vertical radiation pattern of a center fed vertical dipole shown in fig. (A) is for the
dipole length:
(a) 2 (b) 3/2 (c)  (d) 3/4
30. The combined radiation pattern of two non-directional radiators with separation d, fed
with equal currents and with phase shift , (shown in FIG. A) belongs to:
(a) d = /2,  =00
(b) d = /2,  = -900
(c) d = /4,  = -900
(d) d = /4,  =00
FIG. A FIG. B
31. The combined radiation pattern of two non-directional radiators with separation d, fed
with equal currents and with phase shift , (shown in FIG. B) belongs to:
(a) d =,  =00
(b) d = /2,  = -900
(c) d = /4,  = -900
(d) d = /4,  =00
32. An ungrounded antenna near the ground:
(a) acts as a single antenna of twice the height (b) is unlikely to need an earth mat
(b) acts as an antenna array (d) must be horizontally polarized.
33. The standard reference antenna for the directivity is:
(a) Infinitesimal dipole (b) elementary doublet
(c) isotropic antenna (d) half wave dipole

4. 34 A pure sinusoidal continuous variation results in:
(a) Infinite bandwidth (b) Wide bandwidth
(c) Narrow bandwidth (d) Zero bandwidth
35 If Rr is the radiation resistance, T is the antenna temperature, RP indicates the radiation
pattern and f denotes the frequency of operation, identify the correct statement.
(a) All parameters Rr, T and RP are functions of f. (b) Only Rr and T are functions of f.
(c) Only Rr and RP are functions of f. (d) Only RP and T are functions of f.
36 An ungrounded antenna near the ground acts as:
(a) a point source (b) a single antenna of twice of its actual length
(c) an antenna array (d) a single antenna of half of its actual length
37 The directive gain may have a numerical value between:
(a) 0 to 1 (b) 0 to 10 (c) 0 to  (d) –1 to +1
38 The quality factor of an antenna is
(a) Directly proportional to bandwidth (b) Directly proportional to square of bandwidth
(c) Inversely proportional to bandwidth (d) Inversely proportional to square of bandwidth
39 Identify the correct statement:
(a) Time changing current radiates but accelerated charge does not radiate
(b) Time changing current does not radiate but accelerated charge radiates
(c) Both, time changing current and accelerated charge radiate
(d) Both time changing current and accelerated charge do not radiate
40 From the circuit point of view an antenna appears to the transmission line as:
(a) input resistance (b) radiation resistance
(c) mutual impedance (d) coupling impedance
41 If S(, ) is the Poynting vector and S(, )max represents its maximum value the
normalized power pattern is given by:
(a) S(, ) / S(, )max (b) S(, )max / S(, )
(c) S(, )max - S(, ) (d) S(, )max + S(, )
42 The Poynting vector is given by S(, ) = [E2
() + E2
()] / Z0 where Z0 is:
(a) input impedance of the Tx- line (b) input impedance of the antenna
(c) intrinsic impedance of the space (d) combined impedance of Tx-line and antenna
43 If the (total) beam area A (or beam solid angle) consists of the main beam area M plus
the minor-lobe area m (i.e. A = M + m) beam efficiency is given by:
(a) A / M (b) M / A (c) A / m (d) m / A
44 The directivity in terms of beam area A can be written as:
(a) A / 4 (b) 4 / A (c) A / 2 (d) 2 / A
45 If G is the gain k is the efficiency factor and D is the directivity of an antenna these are
related by:

5. (a) G = k2
D (b) G = D / k2
(c) G = D / k (d) G = k D
46 The directivity D of antenna and the number N of the point sources in the sky that can be
resolved by the are related by the equation:
(a) D = N2
(b) D = N (c) D = 1/ N (d) D = 1 / N2
47 The directivity D is given in terms of the antenna aperture Ae by the following relation:
(a) D = 4Ae/2
(b) D = 42
/Ae (c) D = Ae/42
(d) D = Ae/4
48 The field around an antenna may be divided into two principal regions called the near
field or Fresnel zone and far field or Fraunhofer zone. The boundary between the two
regions may be arbitrarily taken at a radius R for an antenna of maximum dimension L,
where R and L are related by:
(a) R = 2L2
/2
(b) R = 2L/2
(c) R = 2L2
/ (d) R = 2L/
49 Antennas act as reflection-less transducers over wide range frequencies if the
discontinuities are:
(a) large and abrupt (b) small and abrupt (c) large and gradual (d) small and
gradual
50 The ratio of the distance between antenna and point of observation of field to the physical
size of an antenna is the deciding factor for considering an antenna to be a point source.
Thus an antenna may be regarded as a point source if this ratio is:
(a) > 1 (b) >> 1 (c) << 1 (d) = 1
51 The standard reference antenna for the directivity is:
(a) Infinitesimal dipole (b) elementary doublet
(c) isotropic antenna (d) half wave dipole

6. SECTION – B
52 The vertical radiation pattern of a center fed vertical dipole shown in fig. (A) is for the
dipole length:
(a) 2 (b) 3/2 (c)  (d) 3/4
53 A dipole antenna is a straight radiator, usually fed in the center. It produces a maximum
of radiation:
(a) in the plane parallel to its axis (b) in the plane normal to its axis
(c) at the place of feed (d) at its extreme ends
54 The bandwidth of a folded dipole in comparison to that of an unfolded dipole is:
(a) About 50% more (b) About 10% more (c) About 50% less (d) About
10% less
55 In relation to the directional characteristics of the dipole antennas the terms ‘theta’ and
‘phi’ polarizations are synonymous with and replace the respective older terms of:
(a) Horizontal and vertical polarizations (b) Vertical and horizontal polarizations
(c) Circular and elliptical polarizations (d) Elliptical and circular polarizations
56 If ‘z’ is the input impedance of a simple dipole, the impedance of n folded dipole is:
(a) n z (b) n2
z (c) z / n (d) z / n2
57 Wire antennas are commonly termed as dipoles provided the wire length is:
(a)  (b) 3/4 (c) /2 (d) /4
58 Identify the correct statement:
(a) The location of feed determines the direction of lobe and orientation of wire determines
the polarization.
(a) The location of feed determines the Polarization and orientation of wire determines the
direction of lobe.
(a) The location of feed determines the direction of lobe and the polarization.
(a) The orientation of wire determines the direction of lobe and the polarization.
59 The thickness of wire influences the characteristics of an antenna particularly its:
(a) Radiation pattern (b) Field pattern (c) Input impedance (d) Radiation
resistance
60 The following terms assigned to an antenna bears the same meaning:
(a) Terminated/standing wave/non-resonant (b) Terminated/traveling wave/resonant
(c) Un-terminated/traveling wave/non-resonant (d) Un-terminated/Standing
wave/resonant
61 Front to back ratio of an antenna can be increased by:
(a) Sacrificing its gain (b) Increasing its size
(c) Using material of high conductivity (d) None of the above
62 An ungrounded antenna near the ground:

7. (a) acts as a single antenna of twice the height (b) is unlikely to need an earth mat
(c) acts as an antenna array (d) must be horizontally polarized.
63 At a sufficient distance R at point O on the observation circle in the far field region of an
antenna:
(a) The radiated fields are radial and the power flow is transverse.
(b) The radiated fields are transverse and power flow is radial.
(c) Both the radiated fields and power floware transverse.
(d) Both the radiated fields and power floware radial
64 A diffracted ray is one that follows a path that:
(a) cannot be interpreted as either reflection or refraction
(b) can be interpreted as either reflection or refraction
(c) can be interpreted as reflection but not as refraction
(d) can be interpreted as refraction but not as reflection
65 The Huygens principle:
(a) Neglects the vector nature of electromagnetic field.
(b) Neglects the effects of current flow at the edges of slot.
(c) Neglects the effects of current flow at the edges of horn.
(d) Neglects all aspects listed in (a, b & c) above.
SECTION – C
ANTENNA ARRAYAS
66 Side lobes in a broad side array will be entirely eliminated provided the spacing between
elements does not exceed:
(a) /4 (b) /2 (c) 3/4 (d) 
67 An array consisting of a number of equidistant dipoles of equal size, fed with the currents
having same amplitude and same phase is:
(a) an end fire array (b) a back fire array (c) a broadside array (d) a
binomial array
68 Select the correct statement.
(a) The end fire directivity is proportional to the square of the array length while the
directivity of the broadside square array is proportional to the side length.
(b) The end fire directivity is proportional to the array length while the directivity of the
broadside square array is proportional to the square of the side length.
(c) The directivity of both end fire and broadside array is proportional to the array
length.
(d) The directivity of both end fire and broadside array is proportional to the square of side
length.

8. 69 Width of principal lobe for uniform BSA with array length nd is reciprocal to:
(a) nd (b) n2
d (c) n2
d2
(d) nd2
70 When the current ratios and phases are properly chosen sharp directivity with an array of
fixed length but sufficiently large number of elements can be obtained. With this phasing and
close spacing between elements the radiation resistance:
(a) Reduces to extremely low value (b) Increases to extremely high value
(c) Remains unaffected (d) Changes slightly
71 The Chebyshev polynomial Tm(x) is commonly used in design and synthesis problems.
For m = 0 and m = 1 its respective values are:
(a) 1 and 0 (b) 0 and 1 (c) 1 and  (d)  and 1
72 An array consisting a no. of equidistant dipoles of equal size, fed with the same currents
and phase is called:
(a) end fire array (b) back fire array (c) broad side array (d) binomial array
73. The width of the major lobe is almost exactly inversely proportional to the array length l, if
(a) l   (b)  < l  3 /2 (c) 3 /2 < l  2 (d) l > 2
74 Side lobes in a broad side array will be entirely eliminated provided the spacing between
adjacent antennas does not exceed
(a)  / 4 (b)  / 2 (c) 3 / 4 (d) 
75 The directional pattern of an end fire array using isotropic radiators is substantially
independent of the spacing of the antenna radiators provided this spacing does not exceed
(a)  / 8 (b)  / 4 (c) 3 / 8 (d)  / 2
76 Choose the correct statement:
(a) Both Binomial and uniform amplitude distributions are special cases of Dolph-
Tchebyscheff distribution.
(b) Both edge and uniform amplitude distributions are special cases of Dolph-
Tchebyscheff distribution.
(c) Both Binomial and edge distributions are special cases of the Dolph-Tchebyscheff
(D-T) distribution.
(d) All the three distributions listed in (a, b & c) above are special cases of Dolph-
Tchebyscheff distribution.

9. SECTION – C
DIFFERENT TYPES OF ANTENNAS
77 The parabola reflects the wave originating from a source at the focus and transforms:
(a) A plane wave front from the feed at focus into spherical wave front
(b) A plane wave front from the feed at focus into cylindrical wave front
(c) Any curved wave front from the feed at focus into a plane wave front
(d) A cylindrical wave front from the feed at focus into a spherical wave front
78 For large parabola of many  aperture a practical choice for feed can be corner reflector
with a corner angle of (depending on F/D ratio of parabola):
(a) 0 - 450
(b) 450
-900
(c) 600
-1200
(d) 900
- 1800
79 Beam widths for corner reflector are approximately equal in both principal planes
provided corner angle  =:
(a) 1200
(b) 900
(c) 600
(d) 450
80 When the field across the mouth of the parabola is everywhere of the same phase the
beam generated
(a) is omni-directional (b) is sharply unidirectional
(c) has main beam with two minor side lobes (d) is bifurcated into two major beams.
81 Antennas commonly used for microwave links are:
(a) Loop antennas (b) Log periodic antennas
(c) Rhombic antennas (d) Paraboloidal dishes
82 Identify the correct statement:
(a) The feed pattern is called primary pattern and the pattern of reflector as secondary
pattern.
(b) The pattern of reflector is the primary pattern and that of feed is termed as secondary
pattern.
(c) Only rear feed pattern is called primary pattern.
(d) Only front feed pattern is called primary pattern.
83 Zoning is used with a dielectric antenna mainly to:
(a) Increase the bandwidth of the antenna (b) Reduce the bulk of the lens
(c) Permit pin pointed focusing (d) Correct the curvature of the wave front from a
short horn
84 The delay lenses wherein the electrical path length is increased or wave is retarded by
the lens medium include:
(a) E-plane metal lenses (b) H-plane metal lenses
(c) Dielectric and H-plane metal lenses (d) E-plane and H-plane metal
lenses.
85 The fast lenses wherein the electrical path length is decreased by the lens medium
include:
(a) Dielectric and E-plane metal lenses (b) E-plane metal lenses
(c) H-plane metal lenses (d) E-plane and H-plane metal

10. lenses.
86 Refraction in the lenses may involve one or two surfaces. The use of lenses having
refraction through two surface is not very common but it offers better performance, prevents
refocusing of energy into the feed and provides wide angle scanning when r is of the order
of:
(a) 3.5 (b) 2.5 (c) 1.5 (d) 0.5
87 Lenses with n > 1 are non-dispersive, their thickness decreases as n increases,
mismatch between lens and free space increases and energy loss due to refraction
increases. The bandwidth of such a lenses in terms of the frequency of operation is about: of
the frequency of operation.
(a) 50% (b) 30% (c) 20% (d) 10%
88 The zoning makes the lens frequency sensitive, increases the energy loss, side lobe level
and the shadowing effect. These effects can be minimized by using a design with:
(a) Large f/D ratio keeping it = 1 (b) Large f/D ratio keeping it  1
(c) Less f/D ratio keeping it = 0.5 (d) Less f/D ratio keeping it < 0.5
89 Identify the correct statement:
(a) In comparison to reflector gain of lens antenna is 1 or 2 dB less, but tolerance on
surfaces is more.
(b) In comparison to reflectors gain and tolerance on surfaces of lens antenna is little more.
(c) In comparison to reflectors gain and tolerance on surfaces of lens antenna is little less.
(d) In comparison to reflectors their gain is 1 or 2 dB more and also have less lenient
tolerance on surfaces.
90 The small loop and short dipole (with loop axis parallel to the dipole) have identical field
patterns for:
(a) E (b) H (c) both E and H (d) E and H interchanged
91 The circular loop of diameter d is generally regarded as small loops if:
(a) d < /2 (b) d < /4 (c) d < /8 (d) d < /10
92 A small rectangular loop with area A satisfies the condition:
(a) A < /10 (b) A < /100 (c) A < 2
/100 (d) A < 2
/10
93 A longitudinal slot in a cylinder has a radiation pattern is practically circular in plane
perpendicular to the axis provided the cylinder diameter in terms of  is of the order of
(a)  / 10 (b)  / 8 (c)  / 4 (d)  / 2
94 The slot and dipole have the same field patterns for:
(a) E alone (b) H alone (c) E as well as H (d) interchanged E and H
95 Identify the correct statement:
(a) The Horizontal slots may result in horizontal polarization and vertical slots in vertical
polarization.
(b) The vertical slots may result in horizontal polarization and horizontal slots in vertical
polarization.
(c) Both vertical and horizontal slots may result in horizontal polarization.

11. (d) Both vertical and horizontal slots may result in vertical polarization.
96 A properly designed slot antenna may have bandwidth of about:
(a)  10 % of center frequency (b)  5 % of center frequency
(c)  2 % of center frequency (d)  1 % of center frequency
97 The sharpest beam and highest gain for a given mouth size of a horn are obtained by
(a) very small flare angles (b) small flare angles
(c) large flare angles (d) very large flare angles
98 A longitudinal slot in a cylinder has a radiation pattern is practically circular in plane
perpendicular to the axis provided the cylinder diameter in terms of  is of the order of
(a)  / 10 (b)  / 8 (c)  / 4 (d)  / 2
99 In an optimum horn the difference in path length along the edge and the center in E plane is:
(a)  /4 (b)  /2 (c)  3/4 (d)  
100 Helical Antennas combine the geometry of a straight line, a circle and a cylinder. These
antennas are:
(a) Circularly polarized with high gain (b) Circularly polarized with low gain
(c) Linearly polarized with high gain (d) Linearly polarized with low gain
101 The axial (end fire) mode of helical antenna is most practical because it can achieve
over a wide band:
(a) Linear Polarization (b) Circular Polarization
(c) Elliptical Polarization (d) All the above
102 In mono-filar helices the term transmission mode is used to describe the manner in
which the electromagnetic wave is propagated along:
(a) A very short helix (b) A medium length helix
(c) A long helix (d) An infinite helix
YAGI-UDA ANTENNA
103 A Yagi antenna may have:
(a) A single director and multiple reflector (b) A single reflector and multiple
directors
(c) Multiple directors and multiple reflectors (d) All the above combinations
WAVE PROPAGATION
104 With vertical polarization the magnitude of reflection coefficient for space wave is
commonly:
(a) quite large at moderately small angles of incidence
(b) quite small at moderately small angles of incidence
(c) quite small at moderately large angles of incidence
(d) quite large at moderately large angles of incidence
105 The conductivity and dielectric constant of earth vary greatly with conditions. At
broadcast band and lower frequencies, the earth can be regarded (approximately) as:

12. (a) pure capacitive (b) pure resistive (c) pure inductive (d) a combination of
R & C
106 At Brewster’s angle the reflection coefficient “Rv” for vertically polarized wave is:
(a) >>1 (b) 1 (c) <<1 (d) 0
107 At Brewster’s angle for vertically polarized wave the phase of reflected wave, from the
earth surface with finite conductivity will differ from the phase of reflected wave from a
surface with infinite conductivity by:
(a) 1800
(b) 900
(c) 450
(d) 00
108 The earth is normally considered to be flat if the distance (d, in miles) between Tx and
Rx does not exceed:
(a) 50/(fMHz)1/4
(b) 50/(fMHz)1/2
(c) 50/(fMHz)1/3
(d) 50/(fMHz)
109 The roughness of earth is generally estimated in terms of conductivity , angle of
incidence  and wavelength  by the Raleigh criterion given by:
(a) R = 4 sin  /  (b) R = 4   sin  /  (c) R = 4   sin  (d) R = 4   sin  /

110 The ionosphere and the earth both act as good reflectors especially in the lower range
of:
(a) VHF (b) HF (c) MF (d) VLF
111 The troposphere extends from earth surface to a height of:
(a) 5 Km (b) 15 Km (c) 50 Km (d) 90 Km
112 Radiated energy in the UHF range propagate by means of:
(a) ground waves (b) sky waves (c) surface waves (d) space
waves
113 Tropospheric scatter is used with frequency in the range of:
(a) VLF (b) HF (c) VHF (d) UHF
114 The temperature of troposphere decreases with height at an average rate of:
(a) 2 degree/km (b) 4 degree/km (c) 6 degree/km (d) 8
degree/km
115 The phenomenon of super refraction occurs only when dM/dh is:
(a) Negative (b) Zero (c) Positive (d) infinite
116 In FIG.C four different paths are adopted by rays for different refractive index variations.
The ray for the condition dM / dh = 0 is:
(a) a (b) b (c) c (d) d
FIG.C

13. 117 The modified refractive index is defined by the relation M =
(a) (n + 1 – h / a)  106
(b) (n + 1 + h / a)  106
(c) (n - 1 – h / a)  106
(d) (n - 1 + h / a)  106
118 When microwave signal follows the curvature of the earth, the phenomenon is called:
(a) Faraday’s effect (b) ducting (c) Tropospheric scatter (d) ionospheric reflection
119 VLF waves are used for some specific applications because:
(a) they easily penetrate ionosphere (b) they require low power
(c) they are very reliable (d) the transmitting antennas are of convenient size
120 The day time broadcasting in 535-1600 kHz range:
(a) completely depends on tropospheric waves (b) ionospheric waves
(c) ground waves (d) does not depend on mode of propagation (listed in a, b, c
above) at all
121 The skip distance for radio wave increases with:
(a) Increase in frequency (b) Decrease in frequency
(c) Atmospheric disturbances (d) Temperature of atmosphere
122 High frequency waves are:
(a) absorbed by F2 layer (b) capable of use for long distance communication on
moon
(c) affected by solar cycle (d) reflected by D layer
123. If wave of critical frequency 30 MHz is departing at an angle of 600
, then the MUF is:
(a) 10 MHz (b) 15 MHz (c) 40 MHz (d) 60 MHz
124 If 0 is the angle of incidence, d is the distance between transmitter and receiver and R
is the radius of earth, the take-off angle  is given by the relation:
(a)  = 90 - 0 - 57.3 d / 2R (b)  = 90 - 0 + 57.3 d / 2R
(c)  = 90 + 0 - 57.3 d / 2R (d)  = 90 + 0 + 57.3 d / 2R