Description : Which ofthe followingcableswill have the highestlaunch power capability? a. 50/125/0.2 b. 85/125/0.275 c. 62.5/125/0.275 d. 100/140/0.3
Last Answer : d. 100/140/0.3
Description : Indicatewhich one ofthe followingreasonsforthe use of a groundscreenwith antennasisfalse: a. Impossibility of a good ground connection b. Provision of an earth for the antenna c.Protectionofpersonnelworkingunderneath d. Improvement of the radiation pattern of the antenna
Last Answer : c.Protectionofpersonnelworkingunderneath
Description : One ofthe followingis not a reason forthe use of anantenna coupler: a. To make the antenna look resistive b. To provide the output amplifier with the correct load impedance c. To discriminate against harmonics d. To prevent reradiation of the local oscillator
Last Answer : d. To prevent reradiation of the local oscillator
Description : Indicatewhich ofthe followingreasonsfor usinga counterpoisewith antenna isfalse: a. Impossibility of a good ground connection b.Protectionofpersonnelworkingunderground c. Provision of an earth for the antenna d. Rockiness of the ground
Last Answer : b.Protectionofpersonnelworkingunderground
Description : One ofthe followingis veryuseful as amultibandHFreceivingantenna.Thisisthe: a. conical horn b. folded dipole c. log periodic d. square loop
Last Answer : c. log periodic
Description : One ofthe followingconsistsof nonresonant antennas: a.The rhombic antenna b. The folded dipole c. The end-fire array d. The broadside array
Last Answer : a.The rhombic antenna
Description : Indicatewhich ofthe followingfrequencies cannotbe used forreliablebeyond-the-horizon terrestrial communicationswithoutrepeaters: a. 20 kHz b. 15 MHz c. 900 MHz d. 12GHz
Last Answer : d. 12GHz
Description : Indicatewhich one ofthe followingterms appliestotroposcatter propagation: a. SIDs b.Fading c. Atmospheric storms d. Faraday rotation
Last Answer : b.Fading
Description : Aship-to-ship communicationssystemisplagued byfading.The bestsolutionseemstobe useof a. a more directional antenna b. a broadband antenna c. frequency diversity d. space diversity
Last Answer : c. frequency diversity
Description : To couple a coaxialline toa parallel-wire line,itisbesttouse a a. slotted line b.balun c. directional coupler d. quarter-wave transformer
Last Answer : b.balun
Description : Fortransmission-line loadmatchingover a range offrequencies,itisbesttouse a a. balun b. broadband directional coupler c. double stub d. single stub of adjustable position
Last Answer : c. double stub
Description : The output from a full wave rectifier is (a) A pulsating uni-directional current (b) A DC voltage (c) Zero (d) An AC voltage
Last Answer : a) A pulsating uni-directional current
Description : Hot rolled sheets have ______ value of permeability (a) zero (b) low (c) high (d) none ofthe above
Last Answer : (b) low
Description : The outer conductor of a coaxial transmission line is always grounded at the A. Input only B. Input and output C. Output only D. Point of high SWR
Last Answer : B. Input and output
Description : Materials subjected to rapid reversal of magnetism should have (a) large area oiB-H loop (b) high permeability and low hysteresis loss (c) high co-ercivity and high retentivity (d) high co-ercivity and low density
Last Answer : (b) high permeability and low hysteresis loss
Description : Magnetising steel is normals difficult because (a) it corrodes easily (6) it has high permeability (c) it has high specific gravity (d) it has low permeability
Last Answer : (d) it has low permeability
Description : Silicon transistors are preferred because: (a) High operating temperature (b) Low leakage current (c) Suited to high frequency circuits (d) All
Last Answer : (d) All
Description : The operational amplifier is _______ (a) High gain amplifier (b) high power amplifier (c)high resistance amplifier (d)low resistance amplifier
Last Answer : a) High gain amplifier
Description : Non-inverting amplifier circuits have _______ (a) Very high input impedance (b) very low input impedance (c) low output impedance (d) none of above
Last Answer : (a) Very high input impedance
Description : Process of conversion low voltage to high voltage is called _______ (a) Rectification (b)forward bias (c) reverse bias (d) amplification
Last Answer : (d) amplification
Description : Thermistor with high negative temperature coefficient are very accurate for measuring low temperature especially near is a. 10 K b. 70K c. 200K d. 35K
Last Answer : c. 200K
Description : A transmission line of unknown impedance is terminated with two different resistances, and an SWR is measured each time. With a 75 Ω termination, the SWR measures 1.5. With a 300 Ω termination, it measures 2.67. What is the impedance of the line? A. 100 Ω B. 212 Ω C. 300 Ω D. 112 Ω
Last Answer : D. 112 Ω
Description : Which of the following best describes a dip-meter? A. An SWR meter B. A counter C. A variable LC oscillator with metered feedback current D. A field strength meter
Last Answer : C. A variable LC oscillator with metered feedback current
Description : Best described a dip-meter. A. A variable LC oscillator with metered feedback current B. An SWR meter C. A counter D. A field strength meter
Last Answer : A. A variable LC oscillator with metered feedback current
Description : Which tester is used to measure SWR? A. Spectrum analyzer B. Multimeter C. Reflectometer D. Oscilloscope
Last Answer : C. Reflectometer
Description : The minimum impedance of a 75 ohm transmission line with a SWR of 2.5 is a) 100 b) 50 c) 25 d) 30
Last Answer : d) 30
Description : The maximum impedance of a 50 ohm transmission line with SWR of 3 is a) 50/3 b) 3/50 c) 150 d) 450
Last Answer : c) 150
Description : Find the reflection coefficient of the wave with SWR of 3.5. a) 0.55 b) 0.23 c) 0.48 d) 0.68
Last Answer : a) 0.55
Description : Given that the reflection coefficient is 0.6. Find the SWR. a) 2 b) 4 c) 6 d) 8
Last Answer : b) 4
Description : A load of 200 ohm is used to match 300 ohm transmission line to achieve SWR=1. Find out the required characteristic impedance of a quarter of a quarter wave transformer connected directly to the load.
Last Answer : Solution :
Description : a) For a transmission line, Find SWR and reflection coefficient R if, i. There is no reflected voltage. ii. Reflected voltage and incident voltage is equal. iii. If reflected voltage=20V and incident voltage=10V. iv. If reflected voltage=10V and incident voltage =20V.
Last Answer : reflection coefficient R=Vr/Vi i. There is no reflected voltage. i.e,Vr=0 R=0 SWR= 1+R/1-R=1 ii. Reflected voltage and incident voltage is equal. Vr=Vi; R=1 SWR= 1+R/1-R=1+1/1-1=infinity iii. If reflected ... and incident voltage =20V. Vr=10 and Vi=20 R=10/20=0.5 SWR= 1+R/1-R=1+.5/1-.5=3
Description : For a transmission line, the incident voltage. Ei = 6V and Er =2V ,Calculate: (i) Reflection Coefficient (ii) SWR
Last Answer : Reflection Coefficient(K) = Er / Ei = 2V / 6V K = 0.333 SWR = 1+K / 1- K = 1+0.333 / 1-0.333 = 1.333 / 0.667 SWR= 1.998
Description : How can a solar array power source be bypassed when the batteries run low?
Last Answer : Ah got it. If anyone else is interested, you need an “automatic transfer switch” – or get a manual one for that mad scientist charm.
Description : The materials having low retentivity are suitable for making (a) weak magnets (b) temporary magnets (c) permanent magnets (d) none of the above
Last Answer : (b) temporary magnets
Description : VLFwaves are used forsome type ofservices because a. of the low powers required b. the transmitting antennas are of convenient size c. they are very reliable d. the penetrate the ionosphere easily
Last Answer : c. they are very reliable
Description : If all your air bottles are at low pressure and there is a blackout how do you start the generators?
Last Answer : If main air bottles are empty, the emergency air bottle can be used to start the main generator. If even the emergency air bottle is empty, then it can be filled by running emergency air compressor ( ... ). Once the emergency air bottle is filled, this air can be used to start the main generator.
Description : hat two factors determine the directivity pattern of the parasitic array?
Last Answer : Length of the parasitic element (tuning) and spacing between the parasitic and driven elements.
Description : What is the ratio of the maximum radiation intensity to the average radiation intensity? A. Aperture gain B. Directivity gain C. Transmission gain D. Power gain
Last Answer : B. Directivity gain
Description : The directivity pattern of an isotropic radiator is A. a figure-8 B. a sphere C. a unidirectional cardioid D. a parabola
Last Answer : B. a sphere
Description : Stacking elements in a transmitting antenna system A. increases the field strength at the receiving antenna B. increases the directivity of the transmitter antenna C. decrease the size of the lobe in the radiation pattern D. both A and B
Last Answer : D. both A and B
Description : The parasitic element of an antenna system will A. decrease its directivity B. increase its directivity C. give the antenna unidirectional properties D. both B and C
Last Answer : D. both B and C
Description : Comparing the signal strength arriving at the driven element from the desired direction to the signal strength reaching the driver from the opposite direction. A. Directivity B. Sensitivity C. Beamwidth D. Front-to-back ratio
Last Answer : D. Front-to-back ratio
Description : Which of the following improves antenna directivity? A. Driven element B. Reflector element C. Director element D. Parasitic element
Last Answer : D. Parasitic element
Description : ______ is the measurement of a unilateral antenna properties of directivity A. Phase angle B. Antenna gain C. Beamwidth D. Bandwidth
Last Answer : C. Beamwidth
Description : What determines the ability of radar to determine the bearing to a target? A. Speed of light B. Speed of target C. Antenna directivity D. Frequency of signal
Last Answer : C. Antenna directivity
Description : How is directivity of a collinear array affected when the number of elements is increased?
Last Answer : Directivity increases.
Description : Define the following terms related to antennas; (i) Antenna resistance (ii) Directivity (iii) Antenna gain (iv) Power density
Last Answer : Antenna Resistance - The resistance of an antenna has two components: 1. Its radiation resistance due to conversion of power into electromagnetic waves 2. The resistance due to actual losses in the ... the transmitter power divided by the surface area of a sphere (4πR2) at that distance.
Description : Define the following terms: (i) Polarization (ii) Antenna gain (iii)Antenna resistance (iv)Directivity
Last Answer : i) Polarization:- It is defined as the direction of electric field vector in the EM wave radiated by the transmitting antenna. ii) Antenna Gain:- Antenna gain is defined as the ratio of ... in only one direction in which the radiation is maximum. That is directivity = Max. directive gain
Description : An antenna has a radiation resistance of 72 Ω a loss resistance of 8 Ω and a power gain of 16. Find efficiency and directivity.
Last Answer : An antenna has a radiation resistance of 72 Ω a loss resistance of 8 Ω and a power gain of 16. Find efficiency and directivity.
Last Answer : A higher directivity is specified by High gain low BW.