Old CM-4228 8-Bay Bowtie analyzed with 4nec2 with an RF Combiner Mod replacing the original Feedline between left & right bays. Ken Nist's CM4228a.ez.nec file was modified, replacing the Feedline with a simple SOURCE wire at the center feedpoint on each 4-Bay stack. This required the use of TWO "EX Cards" vice the usual one EX. For SWR & Impedance measurements, one of the EX Cards must be disabled.
There is very little Net Gain difference up thru Ch51, considering AT LEAST an additional 0.5 dB loss in a typical RF Combiner, although the RF Combiner Mod does provide 1 to 3 dB higher Raw Gain on the lowest channels and 1-3 dB more on the highest. Even better performance should be expected when applied to larger, Super-Sized 8-Bay antennas as the Max Gain moves to a lower frequency.
If one of the Baluns is REVERSED, a DUAL BEAM pattern results, with each beam about 2.4-2.8 dB lower than a single beam and a NULL in between.
NOTE: Charts do NOT include RF Combiner Loss, which is "typically" 0.5 to 1.5+ dB, see: www.antennahacks.com [Back-To-Back Combiner Loss - divide by two.]
Date(s): 27 Mar 2010. Album by holl_ands. 1 - 22 of 22 Total. 918 Visits.
enlarge 155KB, 779x1024 1 CM-4228 8-Bay Bowtie - 3D View RF Combiner Mod replaces Original Feedline.
enlarge 291KB, 1024x696 2 COMPARISONS - UHF Raw and Net Gain: CM4228 w Combiner Mod, CM4228a Nist File, mclapp M4 4-Bay (9.5x9.0) w 2" BowSwp & DblAnglRefl, Kosmic SuperQuad (9.75x9.5 w 2" BowSwp & SnglAnglRefl.