1 #ifdef HAVE_STDLIB_H
2 #include <stdlib.h>
3 #endif
4 #include <stdio.h>
5 #include <math.h>
6 #include <errno.h>
7 #include "yagi.h"
8
9 #include <errno.h>
10
11 /* The maximum gain of a Yagi is given in the ARRL handbook, 1991, pp33-17
12 as 12dB at one wavelength boom length, rising at 2.6 dB
13 each time boom lengtrh is doubled */
14
determine_maximum_gain(double f,double boom_length_in_m)15 double determine_maximum_gain(double f, double boom_length_in_m)
16 {
17 double lambda, wavelengths, max_gain;
18
19 lambda=3e8/f;
20
21 wavelengths=boom_length_in_m/lambda; /* boom length in wavelengths */
22 if(wavelengths < 1)
23 max_gain=8.0;
24 else
25 max_gain = 12.0 + 2.6*log2(wavelengths);
26 #ifdef DEBUG
27 if(errno)
28 {
29 fprintf(stderr,"Errno =%d in determine_maximum_gain() of max_gain.c\n", errno);
30 exit(1);
31 }
32 #endif
33 return(max_gain);
34
35 }
36 /* This is another algorithm. Its not as accurate as above, but it gives the
37 same result form given number of elements. This allows more accurate comparison
38 of fitnesss'es for the GA and -W algorithm, which would otherwise not be possible. */
determine_maximum_gain2(int elements)39 double determine_maximum_gain2(int elements)
40 {
41 double wavelengths, max_gain;
42
43
44 wavelengths=(elements-1)*0.25; /* boom length in wavelengths */
45 max_gain = 12.0 + 2.6*log2(wavelengths);
46 #ifdef DEBUG
47 if(errno)
48 {
49 fprintf(stderr,"Errno =%d in determine_maximum_gain2() of max_gain.c\n", errno);
50 exit(1);
51 }
52 #endif
53 return(max_gain);
54
55 }
log2(double x)56 double log2(double x)
57 {
58 return(log(x)/0.6931471);
59 }
60