UHF 7-Element FLAT LPDA (Log Periodic Dipole Array) vs FFFDLA (Free Form Flat Dipole Logarithmic Array) analyzed using 4nec2 after Optimization using nikiml's Python Scripts.
In an LPDA, the Rear Element Length is about a half-wavelength long at the lowest Frequency (e.g. 470 MHz). Separation between the REAR Element and the NEXT FORWARD is determined by SIGMA = Dij/2*Lj, which (with TAU) directly determines the overall LPDA Length. The "Best" SIGMA is searched for using nikiml's Optimizer.
In the first (Classic LPDA) Analysis below, each subsequent Element Length is shorter than the preceding by the factor TAU and each subsequent Element Spacing is shorter than the preceding, also by the factor TAU = Li/Li+1 = Dij/Djk. Flat Boom Width = Element Width is determined using nikiml's Optimizer.
In the second FFFDLA Analysis, the Spacings between Elements is still reduced by the factor TAU, but the Elements Lengths as well as Element & Boom Widths are FREE FORM, INDEPENDENT Variables, which resulted in some "interesting" (and repeatable) dimensions with just marginally better performance.
====================================== a) Element Width = Boom Width = 1.5 in:
UHF Raw Gain = 7.5 to 8.7 to 8.4 dBi, F/B & F/R Ratio Min = 17.8 dB and SWR (75-ohms) Under 1.6.
====================================== b) Free-Form Dipole Logarithmic Array (FFDLA), Independently Variable Element Widths, Lengths & Boom Width with Log Sigma Separations:
UHF Raw Gain = 7.7 to 8.6 dBi, F/B & F/R Ratio Min = 24.5 dB and SWR (75-ohms) Under 1.5.
Date(s): 14 Jun 2015. Album by holl_ands. 1 - 30 of 30 Total. 1529 Visits.
enlarge 135KB, 1024x741 1 UHF 7-El FLAT LPDA - OPT Element Width = Boom Width = 1.5 in 3D View
enlarge 110KB, 1152x341 2 UHF 7-El FLAT LPDA - OPT Element Width = Boom Width = 1.5 in Front View [1 large square = 1.25 inches]
enlarge 306KB, 1024x860 3 UHF 7-El FLAT LPDA - OPT Element Width = Boom Width = 1.5 in Top View [1 large square = 1.25 inches]
enlarge 177KB, 1024x741 4 UHF 7-El FLAT LPDA - OPT Element Width = Boom Width = 1.5 in UHF Raw Gain = 7.5 to 8.7 to 8.4 dBi UHF F/B & F/R Ratio Minimum = 17.8 dB
enlarge 189KB, 1024x741 5 UHF 7-El FLAT LPDA - OPT Element Width = Boom Width = 1.5 in UHF SWR (75-ohms) Under 1.6
enlarge 221KB, 1024x741 6 UHF 7-El FLAT LPDA - OPT Element Width = Boom Width = 1.5 in UHF Impedance
enlarge 310KB, 1024x1024 7 UHF 7-El FLAT LPDA - OPT Element Width = Boom Width = 1.5 in Azimuthal Pattern at 470 MHz
enlarge 306KB, 1024x1024 8 UHF 7-El FLAT LPDA - OPT Element Width = Boom Width = 1.5 in Azimuthal Pattern at 530 MHz
enlarge 308KB, 1024x1024 9 UHF 7-El FLAT LPDA - OPT Element Width = Boom Width = 1.5 in Azimuthal Pattern at 590 MHz
enlarge 309KB, 1024x1024 10 UHF 7-El FLAT LPDA - OPT Element Width = Boom Width = 1.5 in Azimuthal Pattern at 650 MHz
enlarge 311KB, 1024x1024 11 UHF 7-El FLAT LPDA - OPT Element Width = Boom Width = 1.5 in Azimuthal Pattern at 698 MHz
enlarge 312KB, 1024x1024 12 UHF 7-El FLAT LPDA - OPT Element Width = Boom Width = 1.5 in Azimuthal Pattern at 758 MHz
enlarge 313KB, 1024x1024 13 UHF 7-El FLAT LPDA - OPT Element Width = Boom Width = 1.5 in Azimuthal Pattern at 806 MHz
enlarge 44KB, 791x1024 14 UHF 7-El FLAT LPDA - OPT Element Width = Boom Width = 1.5 in 4nec2 File includes Summary of Dimensions
enlarge 25KB, 791x1024 15 UHF 7-El FLAT LPDA - OPT Element Width = Boom Width = 1.5 in EVAL Summary of Performance
