I've been asked to make my BASIC program work with 300 ohm ladder-line
as well as 450. Here it is. One can see how far off the G5RV matching
section is for the various bands and what adjustment can be made to
improve the G5RV response on certain bands. Once again, these results
are approximations based on EZNEC and must be fine-tuned for perfection.
10 REM This program calculates optimum ladder-line
20 REM lengths given dipole length and frequency
30 CLS
40 INPUT "Enter Frequency in MHz ", freq
50 INPUT "Enter Dipole Length in Feet ", diplenft
60 INPUT "Enter either 450 or 300 for Z0 ", Z0
70 IF Z0 = 450 THEN LLWL = 886
80 IF Z0 = 300 THEN LLWL = 787
90 dipwl = diplenft / (936 / freq)
100 IF dipwl < .5 THEN dipwl = dipwl + 1
110 IF dipwl < 1.5 THEN GOTO 140
120 IF dipwl > 1.5 THEN dipwl = dipwl - 1
130 GOTO 110
140 fedlinwl = .25 - (TAN(2.5 * (dipwl - 1))) / 12.02
150 fedlinft(0) = (LLWL / freq) * fedlinwl
160 FOR i = 1 TO 7
170 fedlinft(i) = fedlinft(0) + i * ((LLWL / 2) / freq)
180 NEXT i
190 PRINT "Imax points (Current Loops) at"
200 FOR i = 0 TO 7: PRINT fedlinft(i), : NEXT i
210 PRINT : PRINT : GOTO 40
220 END
A supporting graphic is on my web page.
73, Cecil, W6RCA, OOTC http://www.geocities.com/CapeCanaveral/8476
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