UHF 15-Element FLAT LPDA (Log Periodic Dipole Array) analyzed using 4nec2 after Optimization using nikiml's Python Scripts.
In an LPDA, the Rear Element Length is about a half-wavelenght 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. "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 Analysis, the Boom Width ALSO was shorter by the same factor TAU, with the REAR Boom Width determined by the Optimizer, resulting in marginally better performance on some Frequencies.
===================================== a) Element Width = Boom Width = 0.75 in:
UHF Raw Gain =10.7 to 11.0 to 10.4 to 11.0 to 10.6 dBi, F/B & F/R Ratio Minimum = 26.9 dB and SWR (75-ohms) Under 1.7.
===================================== b) Tapered Element & Boom Widths:
UHF Raw Gain = 11.1 to 10.7 to 11.4 to 10.4 to 11.0 dBi, F/B & F/R Ratio Min = 27.2 dB and SWR (75-ohms) Under 1.5.
Date(s): 14 Jun 2015. Album by holl_ands. 1 - 30 of 30 Total. 2102 Visits.
enlarge 115KB, 1003x1024 1 UHF 15-El FLAT LPDA - OPT Element Width = Boom Width = 0.75 in 3D View
enlarge 107KB, 1152x335 2 UHF 15-El FLAT LPDA - OPT Element Width = Boom Width = 0.75 in Front View [1 large square = 1.25 inches]
enlarge 166KB, 1152x491 3 UHF 15-El FLAT LPDA - OPT Element Width = Boom Width = 0.75 in Top View [1 large square = 5 inches]
enlarge 173KB, 1024x741 4 UHF 15-El FLAT LPDA - OPT Element Width = Boom Width = 0.75 in UHF Raw Gain =10.7 to 11.0 to 10.4 to 11.0 to 10.6 dBi UHF F/B & F/R Ratio Minimum = 26.9 dB [EVAL Total Gain includes AGT Corr on ALL Freqs]
enlarge 186KB, 1024x741 5 UHF 15-El FLAT LPDA - OPT Element Width = Boom Width = 0.75 in UHF SWR (75-ohms) Under 1.7
enlarge 224KB, 1024x741 6 UHF 15-El FLAT LPDA - OPT Element Width = Boom Width = 0.75 in UHF Impedance
enlarge 291KB, 1024x1024 7 UHF 15-El FLAT LPDA - OPT Element Width = Boom Width = 0.75 in Azimuthal Pattern at 470 MHz
enlarge 291KB, 1024x1024 8 UHF 15-El FLAT LPDA - OPT Element Width = Boom Width = 0.75 in Azimuthal Pattern at 530 MHz
enlarge 292KB, 1024x1024 9 UHF 15-El FLAT LPDA - OPT Element Width = Boom Width = 0.75 in Azimuthal Pattern at 590 MHz
enlarge 290KB, 1024x1024 10 UHF 15-El FLAT LPDA - OPT Element Width = Boom Width = 0.75 in Azimuthal Pattern at 650 MHz
enlarge 293KB, 1024x1024 11 UHF 15-El FLAT LPDA - OPT Element Width = Boom Width = 0.75 in Azimuthal Pattern at 698 MHz
enlarge 294KB, 1024x1024 12 UHF 15-El FLAT LPDA - OPT Element Width = Boom Width = 0.75 in Azimuthal Pattern at 758 MHz
enlarge 296KB, 1024x1024 13 UHF 15-El FLAT LPDA - OPT Element Width = Boom Width = 0.75 in Azimuthal Pattern at 806 MHz
enlarge 68KB, 791x1024 14 UHF 15-El FLAT LPDA - OPT Element Width = Boom Width = 0.75 in 4nec2 File Includes Summary of Dimensions
enlarge 25KB, 791x1024 15 UHF 15-El FLAT LPDA - OPT Element Width = Boom Width = 0.75 in EVAL Summary of Performance
enlarge 130KB, 1003x1024 16 UHF 15-El FLAT LPDA - OPT Tapered Element & Boom Widths 3D View
enlarge 108KB, 1152x333 17 UHF 15-El FLAT LPDA - OPT Tapered Element & Boom Widths Front View [1 large square = 1.25 inches]
enlarge 199KB, 1152x623 18 UHF 15-El FLAT LPDA - OPT Tapered Element & Boom Widths Top View [1 large square = 5 inches]
enlarge 175KB, 1024x741 19 UHF 15-El FLAT LPDA - OPT Tapered Element & Boom Widths UHF Raw Gain = 11.1 to 10.7 to 11.4 to 10.4 to 11.0 dBi UHF F/B & F/R Ratio Minimum = 27.2 dB
enlarge 181KB, 1024x741 20 UHF 15-El FLAT LPDA - OPT Tapered Element & Boom Widths UHF SWR (75-ohms) Under 1.5
