## Example 15.2.1,Pg.no.538¶

In [2]:
import math
ht=36000   #height of satellite in km
f=4000     #freq used in MHz
Gt=15.0    #transmitting antenna gain
Gr=45.0    #receiving antenna gain
#A) Determination of free−space transmission loss
L=32.5+20*math.log10(ht)+20*math.log10(f)
L=round(L,2)
print 'The free−space transmission loss is',L
#B) Determination of received power Pr
Pt=200.0    #transmitted power in watt
Pr_Pt=Gt+Gr-L    #power ration in dB
Pr_Pt_watt=10**(Pr_Pt/10)    #power ratio in watts
#Therefore
Pr=Pt*Pr_Pt_watt*10**12
Pr=round(Pr,2)*10**-12

The free−space transmission loss is 195.67


## Example 15.2.2,Pg.no.539¶

In [3]:
import math
from math import pi,sqrt
f=150.0   #freq used in MHz
d2=50.0   #distance of dipole in km
#Therefore open−ckt voltage induced is given as
Vs=sqrt(30*Pr*1.64)/(d2*10**3)*2/pi
Vs=Vs*10**6
Vs=round(Vs,2)
print 'The open−ckt voltage induced is',Vs,'uV'

The open−ckt voltage induced is 282.42 uV


## Example 15.3.1,Pg.no.545¶

In [4]:
import math
from math import pi
Pt=100    #transmitted power
f=150     #freq used in MHz
d1=20     #height of transmitting antenna in m
Gt=1.64   #transmitting antenna gain
ht=2      #height of receiving antenna in m
d2=40     #distance in km
c=3*10**8
wl=c/(f*10**6)
E0=sqrt(30*Pt*Gt)   #Field strength at a receiving antenna is
ER=(E0*4*pi*d1*ht)/(wl*(d2*10**3)**2)
ER=ER*10**6
ER=round(ER,2)
print 'Field strength at a receiving antenna is',ER,'uV/m'

Field strength at a receiving antenna is 11.02 uV/m


## Example 15.3.2,Pg.no.548¶

In [5]:
import math
from math import sqrt
ht1=100
ht2=60    #antenna heights in ft
dmax_miles=sqrt(2*ht1)+sqrt(2*ht2)
dmax_miles=round(dmax_miles,2)
print 'The maximum range is',dmax_miles,'miles'

The maximum range is 25.1 miles


## Example 15.4.1,Pg.no.560¶

In [6]:
import math
from math import pi
ht=200   #virtual height in km
a=6370   #in km
B_degree=20
B_rad=20*pi/180   #angle of elevation in degree
#The flat−earth approximation gives
d=2*ht/math.tan(B_degree)
d=round(d,1)
print 'd=',d,'km'
#By using radian measures for all angles
d=round(d,1)
print 'd=',d,'km'

d= 178.8 km
d= 10382.4 km


## Example 15.7.1,Pg.no.574¶

In [7]:
import math
from math import pi,sqrt
conductivity = 4    #measured in S/m
rel_permittivity =80
u=4*pi*10**-7
f1=100              #measured in Hz
f2=10**6            #measured in Hz
#A)first it is necessary to evaluate the ratio of conductivity /w*rel permittivity
w1=2*pi*f1
r=conductivity/w1*rel_permittivity
#Therefore we have to use following eq to calculate the attenuation coeff as
a=sqrt(w1*conductivity*u/2)
a=round(a,3)
print 'The attenuation coeff is',a,'N/m'
#By using the conversion factor N=8.686 dB
a_dB=a*8.686
a_dB=round(a_dB,3)
print 'The attenuation coeff in dB/m is',a_dB,'dB/m'
w2=2*pi*f2
r=conductivity/w2*rel_permittivity
a=sqrt(w2*conductivity*u/2)
a=round(a,1)
print 'The attenuation coeff is',a,'N/m'
#By using the conversion factor 1N=8.686 dB
a_dB=a*8.686
a_dB=round(a_dB,1)
print 'The attenuation coeff in dB/m is',a_dB,'dB/m'

The attenuation coeff is 0.04 N/m
The attenuation coeff in dB/m is 0.347 dB/m
The attenuation coeff is 4.0 N/m
The attenuation coeff in dB/m is 34.7 dB/m