[Elecraft] Elecraft CW Net Announcement

[kevin]

Good Evening,

    It was a cool week with some fog, then a thunderstorm with an inch 
of rain.  The forest enjoyed the moisture.  Some of the ferns are 
turning yellow from a few 30 degree nights.  Smoke has returned but not 
as thick as it was last week.

    The sun continues to be moderately active with no X class flares 
predicted.  Solar flux is still high, it is simply less unsteady.  
Nonetheless, there should be QSB and some hissing.  The sun is rapidly 
moving southward.  Sunset is at 8:02 PM, forty minutes earlier than at 
the beginning of August.

    I posted the code necessary to calculate the electric field around a 
1/2 wavelength dipole antenna.  It will be used to create 3D mesh models 
of antenna radiation patterns; then animate them as the user changes any 
one of seven variables.  I have similar code for 1/4 wave verticals and 
1/2 wave loop antennas.  Animating antenna radiation patterns should be 
fun, the UI building less so :)

Please join us on (or near):

14050 kHz at 2200z Sunday (3 PM PDT Sunday)
  7047 kHz at 0000z Monday (5 PM PDT Sunday)

    73,
       Kevin. KD5ONS






-




// dipole.c
// K. J. Rock
// August 25, 2023

// g++ -o dip dipole.c

#include <stdio.h>
#include <math.h>

#define ETA  376.991118308                // characteristic impedance of 
free space
#define RAD 0.017453293                    // radian to degree
#define PI  3.1415926535                     // cherry, of course
#define TWOPI  6.28318530718           // Katzenjammer feast
#define PIOVR2 1.57079632679           // slipped from sill

int main( void )
     {
     float f = 100;                                     // frequency in MHz
     float lambda = 300 / f;                      // wavelength in meters
     float l = lambda / 2;                          // length of antenna 
in meters
     float k = TWOPI / lambda;                 // save some space
     float h = 1.0;                                     // height of 
antenna in wavelengths
     float I0 = 2;                                       // maximum 
current in amperes
     float r = 1000;                                   // distance from 
antenna to observer in meters
     float dTheta = 20.0;                          // azimuth step size
     float dPhi = 5.0;                                // elevation step size
     float scale = 1.0;                               // fudge factor 
for display purposes

     for (float theta=0; theta<180; theta += dTheta)        // azimuth
       {
       for (float phi=0; phi<360; phi += dPhi) // elevation
           {
           float radius = scale * (ETA * k * I0 * l * sin(k * r)
              * sqrt(1 - sin(theta*RAD-PIOVR2) * sin(theta*RAD-PIOVR2) * 
sin(phi*RAD) * sin(phi*RAD))
              * sin(k * h * cos(theta * RAD-PIOVR2))) / (TWOPI * r);

           printf("%7.4f ", radius );               // E(θ,φ)   in 
Volt/meter  or Newton/Coulomb
           }
       printf("\n");
       }

     return 0;
     }