This set of Radar Multiple Choice Questions & Answers (MCQs) focuses on “Radar Transmitters”.
1. Which out of the following is not a linear-beam tube?
a) Klystron
b) Traveling wave tube
c) Twystron
d) Magnetron
View Answer
Explanation: Magnetron is not a linear-beam tube. In the linear-beam tube the electrons emitted from the cathode are formed into a long cylindrical beam that receives the full potential energy of the electric field before the beam enters the RF interaction region.
2. Linear beam tubes can produce higher power than other power sources.
a) True
b) False
View Answer
Explanation: It is true since klystrons are capable of more than a megawatt of average power. High power is a result, in part, of their larger size and high voltages. Thomson-CSF in France produced a UHF klystron that delivered more than one MW CW power. It was 5 m (16.4 ft) long and weighed 1400 kg (3000 pounds).
3. In klystron, what is the quantity of the electron emission density at the surface of the cathode?
a) Lesser
b) Higher
c) None
d) Very high
View Answer
Explanation: The electron emission density at the surface of the cathode is less than that required for the electron beam, so a large area cathode surface is used and the emitted electrons hence converge to high electron density through a narrow beam.
4. In klystron, the multiple RF cavities, which correspond to the LC resonant circuits of conventional lower-frequency amplifiers, amplifiers, are at ____________
a) cathode potential
b) anode potential
c) collector
d) heater
View Answer
Explanation: The multiple RF cavities, which correspond to the LC resonant circuits of conventional lower-frequency amplifiers, amplifiers, are at anode potential. Electrons are not intentionally collected by the anode, as in some other tubes; instead they are removed by the collector electrode after the beam has given up its RF energy to the output RF cavity.
5. In klystron, the process whereby some electrons are speeded up and others slowed down is called as _______
a) amplitude modulation
b) frequency modulation
c) velocity modulation
d) distance modulation
View Answer
Explanation: In velocity modulation some of the electrons are speeded up while the others are speeded down. During the working of a Klystron tube, the electrons from the drift space which are accelerated during the higher peak of the current cycle are able to reach the ones which slowed down during the previous cycle.
6. A long solenoid with iron shielding around its outside diameter surrounds the high power klystron to provide _____________
a) circular electric current
b) axial electric field
c) circular magnetic current
d) axial magnetic field
View Answer
Explanation: A long solenoid with iron shielding around its outside diameter surround the high power klystron to provide an axial magnetic field that confines the electrons to a relatively long, thin beam and prevents the beam from dispersing. Cooling might have to be provided for the electromagnets.
7. What does PPM stands for?
a) Periodic permanent magnet
b) Power protective magnet
c) Precise power magnet
d) Permanent protective magnet
View Answer
Explanation: PPM stands for power permanent magnet. It consists of a series of magnetic lenses. These lenses employ washer-shaped disk magnets separated by iron pole pieces. The PPM replaces the uniform field of a solenoid with a periodic, essentially sinusoidal, field having the same rms value as the uniform field.
8. How can we determine the frequency of klystron?
a) Electron gun
b) Resonant cavities
c) Collector
d) Modulating anode
View Answer
Explanation: The frequency of a klystron is determined by its resonant cavities. When all the cavities are tuned to the same frequency, the gain of the tube is high but the bandwidth is narrow, usually a fraction of one percent for a tube of modest power output. This is called synchronous tuning.
9. What is the method for broadbanding of a multi-cavity klystron?
a) Power tuning
b) Collector tuning
c) Stagger tuning
d) Peak tuning
View Answer
Explanation: Broadbanding of a multi-cavity klystron can be accomplished by stagger tuning the cavities, similar to the method for broadbanding a conventional multistage IF amplifier. Stagger tuning a klystron is not precisely analogous to stagger tuning an IF amplifier because of interactions among the cavities that can cause the tuning of one cavity to affect the tuning of the others.
10. Conventional narrowband klystrons may have their frequency changed mechanically over a relatively wide frequency range.
a) True
b) False
View Answer
Explanation: It is true since a 10 MW peak power klystron, for example, can have an 8 percent bandwidth, as compared to a 200 kW tube which might have a 2 percent bandwidth, and a 1 kW tube having only a 0.5 percent bandwidth. High power multi-cavity klystrons can be designed with bandwidths as large as 10 to 12 percent.
Sanfoundry Global Education & Learning Series – Radar.
To practice all areas of Radar, here is complete set of Multiple Choice Questions and Answers.
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