initial commit / add all books

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diff --git a/2300/CH21/EX21.13.1/Ex21_1.sce b/2300/CH21/EX21.13.1/Ex21_1.sce
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+//scilab 5.4.1

+//Windows 7 operating system

+//chapter 21 Communication Systems

+clc

+clear

+Npe=6*10^10//Npe=peak electron concentration for the E layer in m^-3

+Npf=10^12//Npf=peak electron concentration for the F layer in m^-3

+fCE=9*sqrt(Npe)//fCE=critical frequency for the E layer

+format("v",5)

+disp("MHz",fCE/10^6,"Critical frequency for the E layer is =")

+fCF=9*sqrt(Npf)//fCF=critical frequency for the F layer

+format("v",5)

+disp("MHz",fCF/10^6,"Critical frequency for the F layer is =")

+R=6400//R=radius of the earth in km

+He=110//He=height of the E layer above the earth surface in km

+ime=asind(R/(R+He))//ime=angle corresponding to maximum frequency fmE for E layer in degrees

+format("v",3)

+fmE=fCE*secd(ime)//fmE=maximum frequency reflected from the E layer

+disp("MHz",fmE/10^6,"The maximum frequency reflected from the E layer is =")

+Hf=250//Hf=height of the F layer above the earth surface in km

+imf=asind(R/(R+Hf))//imf=angle corresponding to maximum frequency fmF for F layer in degrees

+format("v",3)

+fmF=fCF*secd(imf)//fmF=maximum frequency reflected from the F layer

+disp("MHz",fmF/10^6,"The maximum frequency reflected from the F layer is =")

+

diff --git a/2300/CH21/EX21.13.2/Ex21_2.sce b/2300/CH21/EX21.13.2/Ex21_2.sce
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+//scilab 5.4.1

+//Windows 7 operating system

+//chapter 21 Communication Systems

+clc

+clear

+R=6400//R=radius of the earth in km

+He=110//He=height of the E layer above the earth surface in km

+ime=asin(R/(R+He))//ime=angle corresponding to maximum frequency fmE for E layer in radian

+format("v",10)

+o=(%pi/2)-ime//o=angle made by the incident ray at the centre of the earth in degrees

+format("v",5)

+L=2*o*R//L=maximum distance between the transmitting and the receiving points on the earth surface for single hop transmission of the radiowave reflected from the E layer

+format("v",5)

+disp("km",L,"The maximum distance for single hop transmission is =")

+//Answer given in textbook is 2459 km which is incorrect as it is actually around 2356 km.

diff --git a/2300/CH21/EX21.13.3/Ex21_3.sce b/2300/CH21/EX21.13.3/Ex21_3.sce
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index 000000000..86ad505d7
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+//scilab 5.4.1

+//Windows 7 operating system

+//chapter 21 Communication Systems

+clc

+clear

+//fc=9*sqrt(Np)

+fc=3*10^6//fc=critical frequency in Hz

+Np=(fc^2)/81//Np=electron concentration at the reflecting point

+//h=height of the reflecting point from the bottom of the layer

+//Np=(5*10^10)+(10^9*h)....(given)

+h=(Np-(5*10^10))/10^9

+H=100//H=height above the surface of the earth in km

+disp("km",h+H,"The required height above the ground is =")