{ "metadata": { "name": "" }, "nbformat": 3, "nbformat_minor": 0, "worksheets": [ { "cells": [ { "cell_type": "markdown", "metadata": {}, "source": [ "

Chapter 23: Ground Wave Propagation

" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "

Example 23-1.1, Page number: 783

" ] }, { "cell_type": "code", "collapsed": false, "input": [ "#Variable declaration\n", "f1 = 0.1 #Frequency (MHz)\n", "f2 = 1.0 #Frequency (MHz)\n", "f3 = 10.0 #Frequency (MHz)\n", "\n", "#Calculations\n", "d1 = 50/(f1**(1.0/3)) #Distance for f1 (miles)\n", "d2 = 50/(f2**(1.0/3)) #Distance for f2 (miles)\n", "d3 = 50/(f3**(1.0/3)) #Distance for f3 (miles)\n", "\n", "#Result\n", "print \"The distance for 100kHz is\", round(d1,2), \"miles\"\n", "print \"The distance for 1MHz is\", d2, \"miles\"\n", "print \"The distance for 10MHz is\", round(d3,2), \"miles\"" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "The distance for 100kHz is 107.72 miles\n", "The distance for 1MHz is 50.0 miles\n", "The distance for 10MHz is 23.21 miles\n" ] } ], "prompt_number": 1 }, { "cell_type": "markdown", "metadata": {}, "source": [ "

Example 23-2.1, Page number: 786

" ] }, { "cell_type": "code", "collapsed": false, "input": [ "from math import pi,sin\n", "\n", "#Variable declaration\n", "f = 3e6 #Frequency (Hz)\n", "sigma = 0.5 #Standard deviation of surface irregularities (unitless)\n", "theta = 30 #Angle of incidence as measured from normal angle (degrees)\n", "c = 3e8 #Speed of light (m/s)\n", "\n", "#Calculations\n", "wave_lt = c/f #Wavelength (m)\n", "R = 4*pi*sigma*sin(theta*pi/180)/wave_lt\n", " #Roughness factor (unitless)\n", "\n", "#Result\n", "print \"The roughness factor is\", round(R,9)" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "The roughness factor is 0.031415927\n" ] } ], "prompt_number": 2 }, { "cell_type": "markdown", "metadata": {}, "source": [ "

Example 23-2.2, Page number: 786

" ] }, { "cell_type": "code", "collapsed": false, "input": [ "from math import pi,sin\n", "\n", "#Variable declaration\n", "f = 10e6 #Frequency (Hz)\n", "sigma = 5 #Standard deviation of surface irregularities (unitless)\n", "theta1 = 30 #Angle of incidence as measured from normal angle (degrees)\n", "theta2 = 45 #Angle of incidence as measured from normal angle (degrees)\n", "theta3 = 60 #Angle of incidence as measured from normal angle (degrees)\n", "c = 3e8 #Speed of light (m/s)\n", "\n", "#Calculations\n", "wave_lt = c/f #Wavelength (m)\n", "R1 = 4*pi*sigma*sin(theta1*pi/180)/wave_lt \n", " #Roughness factor for theta1 (unitless)\n", "R2 = 4*pi*sigma*sin(theta2*pi/180)/wave_lt\n", " #Roughness factor for theta2 (unitless)\n", "R3 = 4*pi*sigma*sin(theta3*pi/180)/wave_lt\n", " #Roughness factor for theta3 (unitless)\n", "\n", "#Result\n", "print \"The roughness factor for 30 degrees is\", round(R1,4)\n", "print \"The roughness factor for 45 degrees is\", round(R2,3)\n", "print \"The roughness factor for 60 degrees is\", round(R3,4)" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "The roughness factor for 30 degrees is 1.0472\n", "The roughness factor for 45 degrees is 1.481\n", "The roughness factor for 60 degrees is 1.8138\n" ] } ], "prompt_number": 4 }, { "cell_type": "markdown", "metadata": {}, "source": [ "

Example 23-2.3, Page number: 787

" ] }, { "cell_type": "code", "collapsed": false, "input": [ "#Variable declaration\n", "f1 = 0.3 #Frequency (MHz)\n", "f2 = 1 #Frequency (MHz)\n", "f3 = 3 #Frequency (MHz)\n", "sigma = 4e-5 #Standard deviation of surface irregularities (unitless)\n", "\n", "#Calculations\n", "x1 = (18e3)*sigma/f1 #Parameter x for f1 (unitless)\n", "x2 = (18e3)*sigma/f2 #Parameter x for f2 (unitless)\n", "x3 = (18e3)*sigma/f3 #Parameter x for f3 (unitless)\n", "\n", "#Result\n", "print \"The parameter x for 0.3MHz is\", x1\n", "print \"The parameter x for 1MHz is\", x2\n", "print \"The parameter x for 3MHz is\", x3" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "The parameter x for 0.3MHz is 2.4\n", "The parameter x for 1MHz is 0.72\n", "The parameter x for 3MHz is 0.24\n" ] } ], "prompt_number": 13 }, { "cell_type": "markdown", "metadata": {}, "source": [ "

Example 23-5.1, Page number: 790

" ] }, { "cell_type": "code", "collapsed": false, "input": [ "from math import pi, sqrt\n", "\n", "#Variable declaration\n", "f1 = 5e3 #Frequency (Hz)\n", "f2 = 50e3 #Frequency (Hz)\n", "f3 = 500e3 #Frequency (Hz)\n", "sigma = 5e-5 #Standard deviation of surface irregularities (unitless)\n", "eps_r = 15.0 #Relative permittivity (unitless)\n", "mu = pi*4e-7 #Absolute Permeability (H/m)\n", "\n", "#Calculations\n", "w1 = 2*pi*f1 #Angular frequency (rad/s)\n", "w2 = 2*pi*f2 #Angular frequency (rad/s)\n", "w3 = 2*pi*f3 #Angular frequency (rad/s)\n", "\n", "\n", "Zs1 = sqrt((w1*mu)/sqrt(sigma**2 + (w1**2)*eps_r))\n", " #Surface impedence for f1 (ohm)\n", "Zs2 = sqrt((w2*mu)/sqrt(sigma**2 + (w2**2)*eps_r))\n", " #Surface impedence for f2 (ohm)\n", "Zs3 = sqrt((w3*mu)/sqrt(sigma**2 + (w3**2)*eps_r))\n", " #Surface impedence for f3 (ohm)\n", "\n", "#Result\n", "print \"The surface impedence for 5kHz is\", round(Zs1,5), \"ohms\"\n", "print \"The surface impedence for 50kHz is\", round(Zs2,5), \"ohms\"\n", "print \"The surface impedence for 500kHz is\", round(Zs3,5), \"ohms\"\n", "\n", "#There has been a numerical mistake in the calculation/substitution of square root of\n", "#(sigma**2 + (w1**2)*eps_r) and in the second case, the mistake in the calculation of\n", "#(w2*mu)/sqrt(sigma**2 + (w2**2)*eps_r)" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "The surface impedence for 5kHz is 0.00057 ohms\n", "The surface impedence for 50kHz is 0.00057 ohms\n", "The surface impedence for 500kHz is 0.00057 ohms\n" ] } ], "prompt_number": 24 }, { "cell_type": "markdown", "metadata": {}, "source": [ "

Example 23-7.1, Page number: 793

" ] }, { "cell_type": "code", "collapsed": false, "input": [ "from math import pi, atan, cos\n", "\n", "#Variable declaration\n", "f = 2.0 #Frequency (MHz)\n", "sigma = 5e-5 #Standard deviation of surface irregularities (unitless)\n", "eps_r = 15.0 #Relative permittivity (unitless)\n", "d = 20e3 #Distance (m)\n", "eff = 0.5 #Antenna efficiency (unitless)\n", "c = 3e8 #Speed of light (m/s)\n", "E1 = 0.5e-3 #Ground wave electric field strength (V/m)\n", "\n", "#Calculations\n", "wave_lt = c/(f*10**6) #Wavelength (m)\n", "x = (18e3)*sigma/f #Parameter x (unitless)\n", "\n", "b = atan((eps_r + 1)/x) #Phase constant (unitless)\n", "\n", "p = (pi/x)*(d/wave_lt)*cos(b) #Numerical distance (unitless)\n", "\n", "A = (2 + 0.3*p)/(2 + p + 0.6*(p**2)) #Reduction factor (unitless)\n", "\n", "E_t = E1 * d/A\n", "\n", "#Result\n", "print \"The Electric field strength at the transmitted end is\", round(E_t,2),\"V/m\"" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "The Electric field strength at the transmitted end is 445.72 V/m\n" ] } ], "prompt_number": 25 } ], "metadata": {} } ] }