Transmission Media and Antenna Systems w/4K1

Question 1

Characteristic Impedance of a coax line

Answer 1

(138/√Er)⦁log(D/d)
D=Outer Conductor diameter
d=inner conductor diameter
Er=Dielectric constant

Question 2

Dielectric Constant of Polyethylene

Answer 2

2.27

Question 3

Line Impedance of a parallel-strip line spaced 1cm apart with length 50cm

Answer 3

Zo=377(w/l)
=377(1cm/50cm)
=7.54 Ω

Question 4

Average power rating of RG 58/Cu

Answer 4

50W

Question 5

Coax used for high temperature

Answer 5

RG-211A

Question 6

Converting between dBm, dBrnC, TLP(transmission level point) and dBrnCO

Answer 6

dBrnC=dBm+90

TLP(dB)=dBrnC-dBrnCO

Question 7

You are measuring noise in a voice channel at a -4 dB test point level, the meter reads -73dBm, convert the reading into dBrnCO

Answer 7

dBrnC=dBm+90
dBrnC=-73dBm+90
dBrnC=17 dBrnC

TLP=dBrnC-dBrnCO
-4dB=17 dBrnC - dBrnCO
dBrnCO=21 dBrnCO

Question 8

Impedance inversion can be obtained by

Answer 8

a quarter wave line

Question 9

The dielectric constants of materials commonly used in transmission lines range from about

Answer 9

1.2 to 2.8

Question 10

Typically, the velocity factor (Vf) of the materials used in transmission lines range from

Answer 10

0.6-0.9

Question 11

For an air dielectric two wire line, the minimum characteristic impedance value is____

Answer 11

Zo=(276/√ϵr)⦁log(2D/d)
for minimum char. impedance, D=d 
therefore, 
Zo=(276/√1)⦁log(2)
Zo=83Ω

Question 12

Reflection coefficient formula

Answer 12

t=(Zl-Zo)/(Zl+Zo)
Zl=Load impedance
Zo=Characteristic impedance

Question 13

Typical characteristic impedance of RG-8A/u

Answer 13

50Ω

Question 14

Characteristic impedance of a quarter-wave transformer

Answer 14

Zo=(276/√ϵr)⦁log(2D/d)

Question 15

Standard tariff for flat rate telephone service beyond normal flatrate in that area

Answer 15

WATS (WIDE AREA TELEPHONE SERVICE )

Question 16

Frequency that’s out -of-band signaling between toll central office (Bell system standard)

Answer 16

3700 Hz

Question 17

If SWR is infinite, what is the type of load?

Answer 17

SWR=Vmax/Vmin
SWR=Zo/Zl
SWR can only be infinite if Zl approx. 0. If Zl is approx. 0, then the load is purely reactive

Question 18

Maximum digit of an international telephone number (CCITT REC.E161)

Answer 18

12 digits

Question 19

One Erlang is equal to___?

Answer 19

36 CCS (Centum Call Second)
1CCS=100 call-seconds
if 1 Erlang is 1 call hour or 1 call-3600 seconds,
simply divide it by 100 to get the equivalent in Centum Cal-Second

Question 20

Standard Telephone Bandwidth

Answer 20

300-3400 Hz

Question 21

Component in telephone set which primary function is for compensation of local loop length

Answer 21

Varistor

Question 22

Receiver used for conventional telephone handset

Answer 22

Electromagnetic

Question 23

Minimum quality circuit available using PTN (packet-based transport networks ()

Answer 23

Basic Voice grade

Question 24

Direct Distance Dialing (DDD) network is called

Answer 24

Dial-up network

Question 25

What special service circuit is connecting two private branch exchange (PBX)

Answer 25

Tie Trunk

Question 26

Power loss in a telephone hybrid

Answer 26

-3dB

Question 27

The first Strowger step-by-step switch was first used in _____

Answer 27

1897

Question 28

What is the CCITT recommendation for a preparation of loss plan, a variable loss plans and a fixed loss plan?

Answer 28

G.122

Question 29

Resistivity constant of copper?

Answer 29

1.7x10^-Ω-m

Question 30

What kind of cell is appropriate for load management, fast moving mobiles and low-usage areas

Answer 30

Umbrella cells

Question 31

Standard base stations are being replaced by what?

Answer 31

adaptive array

Question 32

What is the basis of the first generation wireless loop?

Answer 32

Analog Cellular telephony

Question 33

When a calling party hears a "busy" tone on his telephone, then the call is____

Answer 33

completed

Question 34

Short circuited stubs are preferred to open-circuited stubs because the latter are____

Answer 34

liable to radiate

Question 35

What is the ratio of the reflected voltage to the incident voltage?

Answer 35

coefficient of reflection

Question 36

It is used to determine antenna impedance

Answer 36

Quarter-wave matching

Question 37

Typical coax cable impedance?

Answer 37

50-75Ω

Question 38

Waveguide becomes compulsory to use above what frequencies?

Answer 38

Above 3GHz

Question 39

Nominal voice channel bandwidth

Answer 39

4kHz

Question 40

Echo suppressors are used on all system when the round trip propagation time exceeds ____

Answer 40

50ms

Question 41

Impedance of a quarter wave matching line

Answer 41

Zo'=√(Zo⦁Zl)

Question 42

The apparent speed of propagation along a waveguide based on the distance between wavefronts along the walls of the guide is called

Answer 42

phase velocity