UHF 7-Element Layered LPDA (Log Periodic Dipole Array with Top and Bottom Arrays parallel to each other) was found after trying to Optimize the Wedge version (with Inclusive Angle = 2* HalfAngle) and finding that it was essentially a Layered version...which was then partially Re-Optimized to find the "best" Separation between the Top and Bottom set of LPDA Elements. Python Optimization Scripts from nikiml were used to find the "best" set of dimensions.
Some Parametric Charts for increasing Values of Sigma are found at the bottom. Max Raw Gain reaches 9.0 dBi. SWR (75-ohms) was acceptable for all Wire Sizes, except for larger Sigma's using AWG10 (Relem = 0.051-in). Optimum Boom-Length is a linear function of Sigma (ONLY) with NO difference for various Wire Sizes. Boom-to-Boom Separation increased for low values of Sigma, trying to maintain acceptable SWR, until it becomes excessive for Sigma = 0.02.
Detailed Dimensions for ALL OPTIMIZED LPDA's are included in the below LPDA SPREAD SHEET. These models did NOT include an (Optional) Shorting Stub, and Optimizer ensured that NONE were NEEDED.
More info re Sigma-Tau LPDA Models can be found here: http://www.salsburg.com/Log-Periodic.pdf Additional Design Information is found on fol. webpage for LPCAD...but Sigmas larger than 0.12 were NOT calculated: http://wb0dgf.com/LPCAD.htm
================================================= Two versions are analyzed here: a) 7-El Wedge LPDA and b) 7-El Layered LPDA, with ALL SAME Dimensions, except for Separation between Top & Bottom sets of LPDA Elements.
a) 7-El Wedge LPDA: Dimensions: BoomLength=18.6-in (along the Hypotenuse), Width=12.56-in, Height=0.5-in at Feedpoint rising to 0.71-in at the Rear (very small "Wedge" Angle).
UHF Raw Gain = 7.9 to 9.0 to 8.1 dBi, F/B & F/R Ratio Min = 22.5 dB and SWR (75-ohms) Under 1.8.
=============================================================== b) 7-El Twin-Boom (Layered) LPDA: Dimensions: BoomLength=18.6-in, Width=12.56-in, Height=0.69-in (same all along the Boom).
UHF Raw Gain = 7.9 to 9.0 to 7.9 dBi, F/B & F/R Ratio Min = 21.0 dB and SWR (75-ohms) Under 1.9. [NOTE: More accurate EVAL found only 0.1 dBi less Gain at 698 MHz, see EVAL RESULTS Files.] .
Date(s): 27 Apr 2015. Album by holl_ands. 1 - 39 of 39 Total. 2319 Visits.
enlarge 140KB, 791x1024 1 LPDA SPREAD SHEET Includes Dimensions for All Twin-Boom (Layered) Designs
enlarge 212KB, 1024x742 2 Twin-Boom (Layered) LPDA's Max Raw Gain vs Number of Element Pairs [OPTIMIZED SOLUTIONS] Minimal increase after 15 Element Pairs
enlarge 125KB, 1024x742 3 Twin-Boom (Layered) LPDA's Min F/B & F/R vs Number of Element Pairs [OPTIMIZED SOLUTIONS]
enlarge 154KB, 1024x742 4 Twin Boom LPDA Optimum Boom Length vs Number of Elements Note Linear Relationship
enlarge 159KB, 1024x742 6 7-Element Twin-Boom (Layered) LPDA Max Raw Gain vs Sigma Design Parameter Optimum Sigma = 0.165 [OPTIMIZED SOLUTIONS]
enlarge 153KB, 1024x742 7 7-Element Twin-Boom (Layered) LPDA Tau vs Sigma Design Parameters Note Anomaly at Sigma = 0.08 [OPTIMIZED SOLUTIONS]
enlarge 159KB, 1024x742 8 7-Element Twin-Boom (Layered) LPDA Max SWR vs Sigma Design Parameter SWR for AWG10 (0.051-in) was a bit high. [OPTIMIZED SOLUTIONS]
