# Last graph is plotted with no data points(figure 3) dont know why

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Gophela Seiphepi on 18 Dec 2022
Commented: Gophela Seiphepi on 18 Dec 2022
clc;
clear all;
close all;
% strength of signal is inversely proportional to the distance between Tx
% and Rx
d= 0:1:10
signal_strength = (1)./(d*exp(2)); % where d is the distance between Tx and Rx
figure(1)
plot(d,signal_strength) % simple plot of signal strength vs distance between Tx and Rx
title('Signal Strength against Distance of Transmission')
ylabel('Signal Strength(dBm)')
xlabel('Transmission Distance(kM)')
% signal strength equation
u = 4*pi*10*exp(-7); % constant
c = 3000000; % speed of light in kM per second
P = 500; % power transmission assumed to be 5000 watts
signal_strength_ = sqrt((u*c*P)./(2*pi*d*exp(2)));
figure(2)
plot(d,signal_strength_)
title('Signal Strength against Distance of Transmission')
ylabel('Signal Strength(dBm)')
xlabel('Transmission Distance(kM)')
% Signal Attenuation Plot
Signal_Attenuation = ((signal_strength_-30) / d)
figure(3)
plot(d,Signal_Attenuation)
title('Signal Attenuation vs Distance')
ylabel('Signal Attenuation(dB)')
xlabel('Tx to Rx Distance(kM)')
% signal attenuation plot graph is plotted without any data points and i

Voss on 18 Dec 2022
Signal_Attenuation = (signal_strength_-30) ./ d

Paul on 18 Dec 2022
Hi Gophela,
See below for probable error in calculation of Signal_Attenuation and correction.
clc;
clear all;
close all;
% strength of signal is inversely proportional to the distance between Tx
% and Rx
d= 0:1:10;
d = 1×11
0 1 2 3 4 5 6 7 8 9 10
signal_strength = (1)./(d*exp(2)); % where d is the distance between Tx and Rx
figure(1)
plot(d,signal_strength) % simple plot of signal strength vs distance between Tx and Rx
title('Signal Strength against Distance of Transmission')
ylabel('Signal Strength(dBm)')
xlabel('Transmission Distance(kM)')
% signal strength equation
u = 4*pi*10*exp(-7); % constant
c = 3000000; % speed of light in kM per second
P = 500; % power transmission assumed to be 5000 watts
signal_strength_ = sqrt((u*c*P)./(2*pi*d*exp(2)));
figure(2)
plot(d,signal_strength_)
title('Signal Strength against Distance of Transmission')
ylabel('Signal Strength(dBm)')
xlabel('Transmission Distance(kM)')
Inputs to the Signal_Attenuation compuationg are both 1 x 11
% Signal Attenuation Plot
signal_strength
signal_strength = 1×11
Inf 0.1353 0.0677 0.0451 0.0338 0.0271 0.0226 0.0193 0.0169 0.0150 0.0135
d
d = 1×11
0 1 2 3 4 5 6 7 8 9 10
Using the mrdivide, / operator results in a scalar NaN, I doubt this is the desired result.
Signal_Attenuation = ((signal_strength_-30) / d)
Signal_Attenuation = NaN
Insatead, use element-wise division with the ./ operator, see rdivide, ./
Signal_Attenuation = ((signal_strength_-30) ./ d)
Signal_Attenuation = 1×11
1.0e+03 * Inf 1.8941 0.6653 0.3603 0.2330 0.1661 0.1259 0.0996 0.0813 0.0679 0.0578
figure(3)
plot(d,Signal_Attenuation)
title('Signal Attenuation vs Distance')
ylabel('Signal Attenuation(dB)')
xlabel('Tx to Rx Distance(kM)')
Gophela Seiphepi on 18 Dec 2022
thank you it worked

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