http://www.fortunecity.com/skyscraper/jolt/345/LogCalc.htmlHere's an easy to use log periodic design program. Just plug in the frequency range and the spacing and taper factors and it spits out the element length, and spacing. Chuck/ K1KW uses .933 and .083 for his factors. I find they are a excellent compromise for perfromance vs: boom size.
Below [in meters] are the dimensions for an 18-30 mhz log on a 37' boom. 13 elements. This is considered a long boom log considering it is for 18-30 mhz. Good performance. It is really a clone of Chuck's, but 5 els less and 27' less boom length.
I am now building up two 20M Yagis. So, am considering the 18-30mhz log design below to cover the many bands between 18-30 mhz. Might build up three to stack at 33', 66' and 99'. Good system. Using two booms that act as the feedline and drilling boom holes for direct element connections, it will be quite simple and lighter.
Try the calculator above and plug in your own paramemters for some intersting results. See how easy it is to get a log for 14-30 mhz that can be on a 15' or 200' boom.. :-0 Or a log for 14-14.3 mhz.
73,
Tom, K1JJ
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Here's an effective 18-30 mhz log on a 36.5' boom. 13 elements: [in meters]
Using .933 and .0833
L=el length
R= position on boom
d=spacing between previous el
Number of elements (n): 13
Axial Length: 12.264762149388227
L R d
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1 : 8.76288308 21.71103206 1.454638537
2 : 8.17577016 20.25639352 1.357177796
3 : 7.62799379 18.89921573 1.266246922
4 : 7.11691842 17.63296880 1.181408414
5 : 6.64008509 16.45156039 1.102254083
6 : 6.19519957 15.34930631 1.028403091
7 : 5.78012138 14.32090322 0.959500112
8 : 5.39285341 13.36140310 0.895213632
9 : 5.03153238 12.46618947 0.835234344
10 : 4.69441985 11.63095513 0.779273666
11 : 4.37989385 10.85168146 0.727062352
12 : 4.08644109 10.12461911 0.678349195
13 : 3.81264965 9.446269915 0.632899818
