Winegard HD-8800 (aka PR-8800) 8-Bay FAT Dipoles analyzed using 4nec2.
EZNEC File was downloaded from Ken Nist's HDTVPrimer, Comparing Antennas Webpage: http://www.hdtvprimer.com/antennas/comparing.html [see SIMS link at top] After importing into 4nec2, Ken Nist's INCORRECTLY configured Combining Feedline was Deleted and Replaced by Dual SOURCE "EX" Statements and AutoSegmented.
Ken Niss made a mistake in the Input Feedline Structure, Incorrectly trying to Emulate what an RF Combiner would do, resulting in wildly inaccurate SWR and hence Net Gain results. An RF Combiner matches all Interfaces, whereas Ken's Combiner Network was a simple SHORT. I have now fixed this problem, so Net Gain is only slightly lower than Raw Gain curve.
Note that RF Combiner has a "typical" Insertion Loss of about 0.5 dB in Hi-VHF Band and 1.0 to 1.5+ dB in UHF Band, increasing with Frequency....which REDUCES the fol. Results:
UHF Raw Gain = 13.8 to 16.5 dBi and F/B & F/R Minimum = 12.5 dB with SWR (300-ohms) Under 2.3. Raw Gain on Upper Channels is about 1 dB more than shown in HDTVPrimer and Net Gain is MUCH better, since SWR<2.3 results in Net Gain Loss on Ch14 of only 0.7 dB and
much less for remainder,
no doubt due to eliminating the Feedline Short.
Note that Elevation Pattern Charts showing NULL at about 40-45 degrees.
Date(s): 20 Jan 2017. Album by holl_ands. 1 - 25 of 25 Total. 1715 Visits.
enlarge 123KB, 694x1024 1 Winegard HD-8800 8-Bay FAT Dipoles 3D View Dual SOURCES marked with RED Circles, one at Feedpoint of each 4-Bay.
enlarge 255KB, 1024x861 2 Winegard HD-8800 8-Bay FAT Dipoles Front View [1 large square = 5 inches]
enlarge 77KB, 290x1024 3 Winegard HD-8800 8-Bay FAT Dipoles Top View [1 large square = 5 inches]
enlarge 207KB, 1152x701 4 Winegard HD-8800 8-Bay FAT Dipoles UHF Raw Gain = 13.8 to 16.5 dBi UHF F/B & F/R Minimum = 12.5 dB
enlarge 16KB, 1024x846 25 Winegard HD-8800 8-Bay FAT Dipoles Ken Nist's Erroneous Input Feedline that TRIED to Emulate an RF Combiner. It was replaced by Dual Sources on 4-Bays.
