UHF Channel Master (Old) CM4228 (as built per holl_ands measurements) with Enclosed Bowtie Modification analyzed using 4nec2.
UHF Raw Gain on lowest channels improved about 2 dB at expense of a Gain Dip near 670 MHz. UHF F/B & F/R Ratio was slightly degraded, but SWR was significantly improved.
Hi-VHF Raw Gain significantly improved over the unmodified CM4228, consistently pointing FORWARD with an improved F/B & F/R Ratios, while SWR remained Excessive, which may or may not be an issue in any given situation.
Python Script Optimization should be used to determine "best" Whisker Length and Tine Separation and (why not) also vary the Y-Coord of the Enclosed Wire's mid-point to explore Indented to Pointed (Outdented?) Bowtie shapes. Hopefully the Gain Dip near 670 MHz can be eliminated and the Max Gain moved down to 698 MHz. Might even want to try "Stagger Tuning" with only half of the Bowties Enclosed.
Date(s): 27 Nov 2013. Album by holl_ands. 1 - 11 of 11 Total. 2473 Visits.
enlarge 375KB, 979x1024 1 CM4228 Enclosed Bowtie Mod 3D View
enlarge 371KB, 1008x1024 2 CM4228 Enclosed Bowtie Mod Front View [1 large square = 5 inches]
enlarge 75KB, 287x1024 3 CM4228 Enclosed Bowtie Mod Top View [1 large square = 5 inches]
enlarge 204KB, 1152x689 4 CM4228 Enclosed Bowtie Mod UHF Raw Gain = 13.3 - 15.9 - 14.7 - 17.0 dBi UHF F/B & F/R Minimum = 18.0 dB
enlarge 209KB, 1152x689 5 CM4228 Enclosed Bowtie Mod UHF SWR (300-ohms) Under 2.2
enlarge 251KB, 1152x689 6 CM4228 Enclosed Bowtie Mod UHF Impedance
enlarge 188KB, 1152x689 7 CM4228 Enclosed Bowtie Mod Hi-VHF Raw Gain = 14.2 to 7.1 dBi Hi-VHF F/B & F/R Ratio Minimum = 13.7 dB
enlarge 218KB, 1152x689 8 CM4228 Enclosed Bowtie Mod Hi-VHF SWR (300-ohms) Under 12.5 is EXCESSIVE
enlarge 248KB, 1152x689 9 CM4228 Enclosed Bowtie Mod Hi-VHF Impedance
enlarge 117KB, 791x1024 10 CM4228 Enclosed Bowtie Mod 4nec2 File
enlarge 73KB, 225x1024 11 CM4228 Enclosed Bowtie Mod Side View [1 large square = 5 inches]
