Chapter29 Communication System

Example 29.1 page no 1550

In [4]:
c=3*10**8
f=30.0*10**6
f1=300*10**6
f2=3000*10**6

#Calculation
l=c/f
l1=l/2.0
l2=c/f1
l3=l2/2.0
l4=c/f2
l5=l4/2.0

#Result
print"(i) length of half wave dipole antenna at 30 MHz is",l1,"m"
print"(ii) length of half wave dipole antenna at 300 MHz is",l3,"m"
print"(iii) length of half wave dipole antenna at 3000 MHz is",15,"m"

(i) length of half wave dipole antenna at 30 MHz is 5.0 m
(ii) length of half wave dipole antenna at 300 MHz is 0.5 m
(iii) length of half wave dipole antenna at 3000 MHz is 15 m

Example 29.2 page no 1550

In [8]:
#Given
c=3*10**8                       #m/s
f=3*10**4
f1=6*10**6
f2=5*10**7

#Calculation
l=c/(4.0*f)
l1=c/(4.0*f1)
l2=c/(4.0*f2)

#Result 
print"(i) length of quarter wave dipole antenna at 3*10**4 is",l,"m"
print"(ii) length of quarter wave dipole antenna at 6*10**6 is",l1,"m"
print"(iii) length of quarter wave dipole antena at 5*10**7 is",l2,"m"

(i) length of quarter wave dipole antenna at 3*10**4 is 2500.0 m
(ii) length of quarter wave dipole antenna at 6*10**6 is 12.5 m
(iii) length of quarter wave dipole antena at 5*10**7 is 1.5 m

Example 29.3 page no 1551

In [25]:
#Given
AM=16                        #mV
AM1=4                        #mV

#Calculation
Vmax=AM/2.0
Vmin=AM1/2.0
Ma=(Vmax-Vmin)/(Vmax+Vmin)

#Result
print" The modulation factor is",Ma

 The modulation factor is 0.6

Example 29.4 page no 1551

In [28]:
#Given
Es=50               #V
Ec=100.0            #V

#Calculation
Ma=Es/Ec

#Result
print"The modulation factor",Ma

The modulation factor 0.5

Example 29.6 page no 1552

In [36]:
#Given
Pc=500               #watts

#Calculation
Ps=(1/2.0)*(Pc)
Pt=Pc+Ps

#Result
print"(i) sideband power is",Ps,"W"
print"(ii) power of AM wave is",Pt,"W"

(i) sideband power is 250.0 W
(ii) power of AM wave is 750.0 W

Example 29.7 page no 1552

In [42]:
#Given
Pc=50
Ma=0.8
Ma1=0.1

#Calculation
Ps=(1/2.0)*Ma**2*Pc
Ps1=(1/2.0)*Ma1**2*Pc

#Result
print"total sideband at 80% is",Ps,"KW"
print"total sideband at 10% is",Ps1,"KW"

total sideband at 80% is 16.0 KW
total sideband at 10% is 0.25 KW

Example 29.8 page no 1552

In [47]:
#Given
Fc=500                   #KHz
Fs=1                     #KHz

#Calculation
A1=Fc+Fs
A2=Fc-Fs
B=A1-A2

#Result
print"sideband frequancies are",A1,"KHz and",A2,"KHz"
print"bandwidth required is",B,"KHz"

sideband frequancies are 501 KHz and 499 KHz
bandwidth required is 2 KHz

Example 29.9 page no 1552

In [56]:
#Given
F=10**10                #Hz
D=8*10**3               #Hz

#Calculation
B=2/100.0*10**10
C=B/D

#Result
print"No. of telephones channels are",C*10**-4,"10**4"

No. of telephones channels are 2.5 10**4

Example 20.10 page no 1553

In [80]:
#Given
L=800.0*10**-7
C=3.0*10**8
f1=4.5*10**6                       #Hz

#Calculation
f=C/L
d=(1/100.0)*f
E=d/L
G=d/f1

#Result
print"(i) number of channels for audio signal is",round(E*10**-14,1),"*10**8"
print"(ii) number of channels for video tv signal is",round(G*10**-3,1),"*10**5"

(i) number of channels for audio signal is 4.7 *10**8
(ii) number of channels for video tv signal is 8.3 *10**5

Example 20.11 Page no 1565

In [85]:
#Given
R=6400*10**3                     #m
h=160

#Calculation
import math
d=math.sqrt(2*R*h)
h2=4*h

#Result
print"Height is", h2,"m"

Height is 640 m

Example 20.12 Page no 1565

In [93]:
#Given
R=6.4*10**6                         #m
h=110

#Calculation 
import math
d=(math.sqrt(2*R*h))*10**-3
P=math.pi*d**2

#Result
print"Population covered is", round(P*10**-3,1),"*10**6"

Population covered is 4.4 *10**6

Example 20.13 Page no 1565

In [99]:
#Given
R=6.4*10**6                  #m
hr=50                        #m
ht=32                       #m

#Calculation
import math
d=math.sqrt(2*R*ht)+math.sqrt(2*R*hr)

#Result
print"Maximum distance is", round(d*10**-3,1),"Km"

Maximum distance is 45.5 Km

Example 29.14 Page no 1566

In [107]:
#Given
h=300
R=6.4*10**6                       #m
N=10**12

#Calculation
import math
d=math.sqrt(2*R*h)
fc=9*N**0.5

#Result
print"fc=", fc*10**-6,"MHz"
print"5 MHz comes via ionospheric propogation.and 100 MHz signal comes via satellite transmission."

fc= 9.0 MHz
5 MHz comes via ionospheric propogation.and 100 MHz signal comes via satellite transmission.