UHF 8-Element LPDA (Log Periodic Dipole Array) by VA3RR (and GHZ24) analyzed using 4nec2 for three different models, based on three different physical implementations:
a) 4nec2 File from VA3RR's webpage, which uses SIMULATED Zig-Zag Transmission Line (TL). I re-segmented and formatted to my usual 4nec2 format: http://www.qsl.net/va3rr/hdtv/HDTV.htm This version has also been used by GHZ24 as a Parabolic Reflector antenna Feed.
Beamwidth is very wide 60-70 degrees. Note small glitch near 698 MHz for Raw Gain, F/B and F/R Ratios. Although probably not large enough to cause problems, this can be cured by adding a shorting stub:
UHF Raw Gain = 7.2 - 7.7 dBi, F/B & F/R Ratio Min = 14 dB (most above 20 dB) and SWR Under 1.3.
====================================== b) An LPDA was fabricated by user "oldsparks" using 7/32-in Twin-Boom and AWG10 Elements rather than Zig-Zag Transmission Line (which would be more difficult to construct). It loses about 0.5 dB in the process:
UHF Raw Gain = 6.8 - 7.3 dBi, F/B & F/R Ratio Min = 14 dB and SWR Under 1.2.
====================================== c) Since 7/32-in Twin-Boom is a bit of an overkill, a similar LPDA was analyzed using AWG10 for the Twin-Boom as well as the Elements, plus a Shorting Stub. Dimensions were determined using nikiml's Python Optimization Scripts, providing flatter Gain, higher F/B & F/B Ratios and low SWR:
UHF Raw Gain = 7.3 - 7.8 dBi, F/B & F/R Min = 22.4 dB and SWR Under 1.4.
Date(s): 25 May 2013. Album by holl_ands. 1 - 45 of 45 Total. 3258 Visits.
enlarge 61KB, 1152x203 2 UHF 8-El LPDA - VA3RR Zig-Zag TL Front View [1 large box = 1.25 inches]
enlarge 258KB, 913x1024 3 UHF 8-El LPDA - VA3RR Zig-Zag TL Top View [1 large box = 1.25 inches]
enlarge 196KB, 1152x678 4 UHF 8-El LPDA - VA3RR Zig-Zag TL UHF Raw Gain = 7.2 - 7.7 dBi, but is a bit uneven, with Glitch near 698 MHz F/B & F/R Ratio Min = 14 dB
