Macro Integrated Training and Review Center PERIODIC EVALUATION EXAMINATION 2 TOPIC Tran!"i!!ion Tran!"i!!ion Line!# Antenna# Antenna# Microwave# Satco"
COMMUNICATIONS ENGINEERING
INSTRUCTION Select Select the correct correct answer for each of the followin following g questions questions.. Mark only one answer answer for each item by shading shading the box correspondi corresponding ng to the letter of your choice on the answer answer sheet provided. STRICTL$ NO ERASURES ALLO%ED. ALLO%ED. Use pencil no. 2 only.
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2.
t !"fa !"fact ctor or of 2#$% 2#$% micro microwav wave e ray.. ray.... .. a. travels straight c& 'end! awa( )ro" eart* !+r)ace
b. bends toward earth surface d. goes down
&hich &hich coax coaxial ial cable cable is sexles sexless' s' a. (ayonet )avy *onnector c. Sub"Miniature ssembly
'& A",*eno- Preci!ion Connector d.+hreaded )avy *onnector
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+he beam voltag voltage e at which which microwav microwave e oscillatio oscillations ns in a magnetro magnetron n ,at its pi modemode- start. start. a& .artree vo-tage b. ot cutoff voltage c. Startup voltage d. threshold voltage
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+he two two principal principal operati operation on modes modes in a 0unn 0unn diode that that results results in microwav microwave e oscillati oscillations ons a& TT and LSA b. S and uenched c. ++ and delayed d. uenched and delayed
3.
+unne +unnell diodes diodes can can functi function on as micro microwav wave.. e.... .. a. amplifiers c. rectifiers
b. oscillators d& a or '
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+he microwav microwave e signal to be amplified amplified by a multicavity multicavity klyst klystron ron is fed into the klystron klystron5s. 5s.... ... a& '+nc*er cavit( b. intermediate cavity c. cathode d. catcher cavity
6.
7ind the the equivalen equivalentt annual annual outage outage for 88.889 88.889 availabl available e microwave microwave link a. 323.4 minutes b. 3.24 min c& /2&/0 "in+te! d. 3234 minutes
:.
&hich propagat propagation ion problem problem is not paid attention attention to in fixed microwav microwave e communicati communications ons system' system' a. fading '& Do,,-er !*i)t c. attenuation d. ;ayleigh
8.
&hat microwave microwave band is popular popular for satellite satellite crosslink crosslinks' s' a. / 0< to : 0< b. 12 0< to 1: 0< c& /1 to 02 G. d. 1/= to 14= 0<
1=. ;adomes ;adomes can can be applied applied on .... .... a. te terrestria rial mi microwave an antennas c. shipboard aperture antennas
b. ap aperture >t >type airborne an antennas d& a-- o) t*e a'ove
11. 11. *arcinotro *arcinotrons ns are tube..... tube..... a& o!ci--ator! c. amplifiers
b. resonators d. mixers
12. Solve for the cutoff cutoff wavelength wavelength of a / cm by 4 cm rectangular waveguide waveguide operated at the dominant mode. a. 1= cm '& 32 c" c. : cm d. 1/ cm 1$. n ? band radar operate operates s in which which frequency frequency band' a. 1"2 0< b. /" : 0< c& 14 32 G. d.. 12 "1: 0< 1/. low noise% low power% power% narrow band microwave microwave amplifier utili
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Macro Integrated Training and Review Center 1:. &hat band is immune to terrestrial Damming but sensitive to atmospheric conditions such as transient noise' a& 8+4'and b. !a"band c. *"band d. !"band 18. 7or a rectangular waveguide with a wall separation of $ cm and a desired frequency of operation of 4 0<% determine the group velocity' a. 3./$ x1=: m#s b. 12.3 x 1=6 m#s c& 3&00 9 3:1";! d. 23.$ x 1=3 m#s 2=. &hat is the common up"converter and down converter B7' a. $4 M< '& 5: M. c. /= M< d. 3== M< 21. Medium Farth Grbit ,MFG- satellite operates in the HHHHHfrequency band ,pril% 2==3a. 2"1: 0< '& 3&243&00 G. c. 1"2.3 0< d. 4"12 0< 22. &hat is the reliability of a system with a fade margin of /: d(' a. 88.88 9 b. 88.8 9 c& 66&666< d. 88.88889 2$. 7ade margins of most analog systems are within the range ofHHHHH. a. $="3= d( '& 7/4/: d= c. 13 "$= d( d. 13 "23 d( 2/. *alculate the cut"off wavelength of a circular waveguide with an outside diameter of 1= cm and thickness of 1 cm. a& 37&0/ c" b. 16.$3 cm c. 23.1$ cm d. 12.4$ cm 23. 0unn Ciode is also calledHHHHHHH. a& TED c. CF+
b. d.
FC+ @istol
24. 0unn device has an operating frequency of 1/ 0<% what will be the thickness of the device' a. 4.12 um b. 1=.1/ um c. 12.$4 um d& 5&3> +" 26. &hat frequency does oxygen causes excessive attenuation' a. 8= 0< b. 6= 0< c. := 0< d& 0: G. 2:. HHHHHHHHis a waveguide termination a. stone c. resistor
'& d.
Car'on wedge Silver stub
28. &hat is the best topographic map scale used in path profiling' a. 1I3=== '& 3 /:::: c. 1I 23=== d. 1I 1===== $=. +he use of redundant system to reduce the effects of fading a. redundancy '& diver!it( c. 1J1 system d. duplication $1. &hat is the offset for A7 repeaters' a. 1= M< c. $ M<
'& d.
/ M. 12 M<
$2. n important operational point with the S@CF system is that the carriers are HHHH. a. Voice o,erated b. suppressed c. terminated d. modulated $$. Satellite"to"satellite link is also called a. *oupled link c& Cro!! -in?
b. d.
+raffic link & eakest link
$/. ccording to 7** ,18:$-% what is the minimum orbital spacing for satellites in the !u"band a. 1 degree '& 3&/ degree! c. 2 degrees d. 2.3 degrees $3. AS+ stands forHHHHHHHHHHHHH. a. A7 southband antenna tracking c& Ver( !"a-- a,ert+re ter"ina-
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A7 satellite Aery stylish antenna tin
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Macro Integrated Training and Review Center $4. +he earth is considered asHHHHHHHHHHHH. a. @erfectly spherical b. c& O'-ate !,*eroidad.
@rolate spheroidal @erfectly conical
$6. +he point on the earth5s surface vertically under the satellite is referred to asHHHHHHHHH. a. Spot beam b. Under"satellite point c& S+'4!ate--ite ,oint d. footprint $:. Comsat isHHHHHH. a. Comain satellite c& Do"e!tic Sate--ite
b. d.
Come"shape satellite Coming5s Satellite
$8. +he @hilippines5 gila2 satellite is located at HHHHHHHHH. a. 1/$K F '& 3>0@ E c. 1/8K F d. 132K F /=. Farth surface as seen by a microwave ray% is effectively flattened out at k"factor equals... a. = '& in)init( c. 1 d. /#$ /1. Bf the radius of the first fresnel
1I2 1Iα
/6. &hat is the reflection coefficient for a transmission line with incident voltage of /A and reflected voltage =.63A' a. 2= b. 2 c& :&2 d. 3 /:. Bf the 2 towers of a 2 M< antenna are separated by 12= electrical degrees. &hat is the tower separation in feet' a. 13= ft b. 23= ft c. /82 ft d& 35: )t /8. quarter"wave stub could be used to a. Bncrease the S&; c. ct as aninsulator or short circuit
'& d.
Decrea!ed t*e S%R ll of the above
3=. n antenna transmission line is cut to1#/ wavelength and shorted at one end. +he impedance at the other end is a. high '& -ow c. Fqual to Lo d. Fqual to of Lo 31. technique that can be used to locate impairment in a metallic cable isHHHHHH. a. @eak detection b. ;* c. ;* d& TDR 32. transformer used to match a balanced transmission line to an unbalanced line a. uto transformer b. Stub transformer c. uarter"wave transformer d& 'a-+n 3$. &aveguide and coaxial lines are often pressured with a. hydrogen b. c. helium d& 3/. )itrogen is placed in transmission lines toI a. Bmprove the skin"effect of microwaves b. c. ;educe the standing wave ratio of the d& line
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oxygen nitrogen ;educe arcing in the line Prevent "oi!t+re )ro" entering t*e -ine
Macro Integrated Training and Review Center 33. form of transmission line used at high U7 and microwave frequencies sandwiched between to ground planes and separated from each by a dielectric a& Stri, -ine b. microstrip c. *oaxial line d. +win lead transmission line 34. &hy is coaxial cable no longer used at microwave frequencies' a. (& b. ow impedance c& .ig* atten+ation d. igh coast 36. Cistance traveled by a wave in the time of one cycle a. hop b. c& wave-engt* d.
frequency crest
3:. shorted transmission line less than quarter wavelength will exhibitHHHH reactance a& ind+ctive b. capacitive c. Maximum d. minimum 38. Cielectric designation @+7F,@olytetrafluoroethylene- is another name for a& te)-on b. rubber c. silica d. foam 4=. +he wave that lies down and dies is calledHHHHHHwave. a& gro+nd b. sky c. space d. 1== 41. Ciffraction of electromagnetic waves a. Bs caused by reflection from the ground b. rises only with spherical wavefronts c. &ill occur when the waves pass through a large slot. d& Ma( occ+r aro+nd t*e edge o) a !*ar, o'!tac-e& 42. ine of sight communication is not a factor in which frequency range' a. U7 '& . c. S7 d. Microwaves 4$. +he intrinsic impedance of free space is a. 1Ω c& 32:
b. d.
/πΩ $ x 1=
:
Ω
4/. Bn the 7 range the received signals are mainly byHHHHH a& Gro+nd wave b. Sky wave c. Space wave d. Super refraction 43. law of refraction in wave propagation a. uygen5s principle c. 7araday5s law 44. law of diffraction in wave propagation a& .+(genB! ,rinci,-e c. Snell5s law
'& d.
b. d.
Sne--B! -aw Maxwell5s equation
Maxwell5s equation 7resnel5s law
46. *ircular polari
b. d.
&ave propagation Censity of ioni
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b. d.
Skip distance superrefraction
48. +he field strength of a free space signal is measured as 2 µA#m at a distance of :3%=== km. &hat is the transmitter power' a. 34$ & b. 4== & c. 84$ & d. 1=== & 6=. &hat is the change in the power density when the distance from the source increases by a factor of /' a. 1#2 b. 1#/ c. 1#: d. 1#14 3 61. resonant half"wave dipole in free space has a feed line current of 1. ow much power appears at the input to the feed point' a. 6$ & b. 1/4 & c. 218 & d. 282 & 62. Bf a field intensity of 23mA#m develops 2.6A in a certain antenna% what is its effective height' a. 3 ft b. 1=: m c. 1=:ft d. 3 m
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Macro Integrated Training and Review Center 6$. +he layer of the ionosphere also known as !ennely"eaviside layer. a. C b. F c. 71 d. 72 6/. +he efficiency of an antenna is :29. Bts radiation resistance is $= Ω. &hat is the value of its loss resistance' a. 63 Ω b. 13 Ω c. 12 Ω d. 4.3: Ω 63. ntennas commonly used for microwave links are a. oop antennas c. og"@eriodic ntennas
b. d.
@arabolic Cishes ;hombic ntennas
64. loop antenna is commonly used for a. ;C; c. Satellite communication
b. d.
Cirection 7inding SG);
66. n antenna that is circularly polari
b. d.
og periodic elical
6:. &hich is non"resonant antenna' a. (roadside ntenna c. 7olded dipole
b. d.
;hombic ntenna Fnd 7ire rray 4 68. directional antenna with two or more elements is known as a,na. 7olded dipole b. oop c. 0round plane d. rray :=. &hat is the power gain in db for an antenna with directive gain of /=d( and an efficiency of 439' a. $:.1$d( b. $1.:$d( c. 24d( d. /=d( :1. paraboloid is to have a power gain of /1.33d(. Bf the frequency of operation is to be : 0<% &hat is the diameter of the parabolic reflector' a. 1=ft b. 4ft c. 2.$ft d. 1:ft :2. pulse is transmitted in a cable that has a velocity of propagation of =.$c. +he reflected signal is received $ usec later. ow far down the cable is the impairment' a. 1$3 m b. 26= m c. 24= m d. 113 m :$. Usually when a corona occurs% it meansO. a. the wire has dissipated full power '& t*e tran!"i!!ion -ine i! de!tro(ed c. a new king is crowned d. coronation night :/. +he microwave signal to be amplified by a multicavity klystron is fed into the klystron5sHHHHHHHHH. a. =+nc*er cavit( b. *atcher cavity c. +ooth cavity d. Bntermediate cavity :3. *alculate the approximate distance of a geostationary satellite from an earth station whose transmit antenna is inclined 1: degrees. a. $/4== km b. $34== km c& 770:: ?" d. $14== km
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Macro Integrated Training and Review Center
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