134. At different frequencies microwave impedance measurement is possible with the help of
A. a spectrum analyzer
B. a travelling detector and other auxiliary apparatus
C. either of the above
D. none of the above

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135. The primary purpose of the helix in a travelling wave tube is to
A. reduce the noise figure
B. ensure broadened operation
C. reduce the axial velocity of the RF field
D. prevent the electron beam from spreading in the long tube

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136. a magic tee is nothing but a modification of
A. H - plane tee
B. E ? plane
C. two E - plane tees
D. A combination of E-plane and H-plen tee

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137. A cavity can be considered as
A. band pass filter
B. band stop filter
C. high pass filter
D. low pass filter

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138. Waveguides are generally not made of
A. Copper
B. Bronze
C. Aluminium
D. Any of the above material

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139. Which of the following microwave tube is based on the principle of velocity modulation?
A. TWT
B. Pencil triode
C. Magnetron
D. Klystron

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140. Bolometers are used in measurement of
A. RF power
B. audio power
C. microwave power
D. none of the above

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