Answer by true or false
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Transcribed Image Text:Answer all the questions
Q1) Answer by true or false for ten of the following items, and correct the false one
1- In an array antenna, when the spacing between elements is A/2, the steening of henm
restricted to about +50
2- In an array antenna, the phase shifters are used to reduce sidelobes.
3- The larger the antenna aperture leads to greater gain and wider beamwidth.
4- The smooth walls hom antenna has smaller sidelobe level compared to corrugated horn
antenna.
5- The parabolic surface, which is obtaized by rotating a parabolic curve on its axis,
satisfies the equation (y=6 ).
6- Typical methods used for array synthesis are, the cosine tapering and cosine squared
tappering
7- The condition for bending the clectromagnetic waves down to earth is curvature of the
earth.
The main reason that causing travelling wave attenuation, is the presence of ionized
layers.
The réception of long sky wave is better through the night than the daytime because of
the radiation of the sun.
r10- The propagation of short sky wave depends on some factors, which are eddy currents,
clouds, and gamma rays.
11- The methods used for VHF propagation are tropospheric scatter, ionospheric scatier,
and meteor trails.
12- Trapping usually occurs at millimeters wavelengths.
13- lonization columns produced by meteors in the E-layer region are capable of reflecting
waves. The meteor trails are either of high density or of low density. The probability
of occurrence of the latter is high.
20 Marks
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