Transmission Media and Antenna Systems w/4K1 Flashcards
Characteristic Impedance of a coax line
(138/√Er)⦁log(D/d)
D=Outer Conductor diameter
d=inner conductor diameter
Er=Dielectric constant
Dielectric Constant of Polyethylene
2.27
Line Impedance of a parallel-strip line spaced 1cm apart with length 50cm
Zo=377(w/l)
=377(1cm/50cm)
=7.54 Ω
Average power rating of RG 58/Cu
50W
Coax used for high temperature
RG-211A
Converting between dBm, dBrnC, TLP(transmission level point) and dBrnCO
dBrnC=dBm+90
TLP(dB)=dBrnC-dBrnCO
You are measuring noise in a voice channel at a -4 dB test point level, the meter reads -73dBm, convert the reading into dBrnCO
dBrnC=dBm+90
dBrnC=-73dBm+90
dBrnC=17 dBrnC
TLP=dBrnC-dBrnCO
-4dB=17 dBrnC - dBrnCO
dBrnCO=21 dBrnCO
Impedance inversion can be obtained by
a quarter wave line
The dielectric constants of materials commonly used in transmission lines range from about
1.2 to 2.8
Typically, the velocity factor (Vf) of the materials used in transmission lines range from
0.6-0.9
For an air dielectric two wire line, the minimum characteristic impedance value is____
Zo=(276/√ϵr)⦁log(2D/d) for minimum char. impedance, D=d therefore, Zo=(276/√1)⦁log(2) Zo=83Ω
Reflection coefficient formula
t=(Zl-Zo)/(Zl+Zo)
Zl=Load impedance
Zo=Characteristic impedance
Typical characteristic impedance of RG-8A/u
50Ω
Characteristic impedance of a quarter-wave transformer
Zo=(276/√ϵr)⦁log(2D/d)
Standard tariff for flat rate telephone service beyond normal flatrate in that area
WATS (WIDE AREA TELEPHONE SERVICE )
Frequency that’s out -of-band signaling between toll central office (Bell system standard)
3700 Hz
If SWR is infinite, what is the type of load?
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
Maximum digit of an international telephone number (CCITT REC.E161)
12 digits
One Erlang is equal to___?
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
Standard Telephone Bandwidth
300-3400 Hz
Component in telephone set which primary function is for compensation of local loop length
Varistor
Receiver used for conventional telephone handset
Electromagnetic
Minimum quality circuit available using PTN (packet-based transport networks ()
Basic Voice grade
Direct Distance Dialing (DDD) network is called
Dial-up network
What special service circuit is connecting two private branch exchange (PBX)
Tie Trunk
Power loss in a telephone hybrid
-3dB
The first Strowger step-by-step switch was first used in _____
1897
What is the CCITT recommendation for a preparation of loss plan, a variable loss plans and a fixed loss plan?
G.122
Resistivity constant of copper?
1.7x10^-Ω-m
What kind of cell is appropriate for load management, fast moving mobiles and low-usage areas
Umbrella cells
Standard base stations are being replaced by what?
adaptive array
What is the basis of the first generation wireless loop?
Analog Cellular telephony
When a calling party hears a “busy” tone on his telephone, then the call is____
completed
Short circuited stubs are preferred to open-circuited stubs because the latter are____
liable to radiate
What is the ratio of the reflected voltage to the incident voltage?
coefficient of reflection
It is used to determine antenna impedance
Quarter-wave matching
Typical coax cable impedance?
50-75Ω
Waveguide becomes compulsory to use above what frequencies?
Above 3GHz
Nominal voice channel bandwidth
4kHz
Echo suppressors are used on all system when the round trip propagation time exceeds ____
50ms
Impedance of a quarter wave matching line
Zo’=√(Zo⦁Zl)
The apparent speed of propagation along a waveguide based on the distance between wavefronts along the walls of the guide is called
phase velocity
