Old CM4228 (holl_ands) with Screen Reflector analyzed using 4nec2.
Measurements derived from an Actual CM4228 I bought in 2008, importing Horizontal Harness from Ken Nist's cm4228a.eznec file. Note small differences in some dimensions compared to Ken Nist's:
BowLength = 8.0-in, Bowtie Spacing = 8.0-in, Tine Separation = 5.25-in. Approx. AWG10 wire size (0.102" O.D.). Feedline Separation = 1.3-in, with 0.7-in Hop at Crossover. AWG12 wire size (0.088" O.D.). Center of Crossovers 2.1-in from Center of Outer Bowties. Left to Right Bay Separation = 20-in. Screen Reflector (36"H x 40"W), AWG12, 1"H x 2"W Grid. Separation from Bowties = 4.6-in (varies 4.5-4.75-in).
UPDATE (3Dec2011): Added 4nec2 analysis if MOVE Horizontal Harness from between Screen Grid and Bowties to new location IN FRONT of Bowties. Although SWR just above 470 MHz was slightly improved, Gain on 470 MHz dropped by 1 dB with reduced F/B and F/R Ratios. So modification did NOT improve overall performance.
UPDATE (9Dec2011): Added 4nec2 analysis for Hi-VHF. Note that there are separate 4nec2 files for UHF and Hi-VHF frequency bands. A deep Gain Hole was found on Ch11 and SWR was EXCESSIVE across entire Hi-VHF Band.
EDIT (29Mar2013): Added ANOMALOUS plots versus Bowtie Tine Separation and Bowtie Forward Sweep, which can frustrate finding an "Optimum" set of dimensions. I believe that this is a 4nec2 Modeling anomaly, rather than inherent in old CM4228 design. It's unlikely Whisker movements of under 0.25-in result in significant Gain changes.
EDIT (10Jun2014): Added Grid Size Effectiveness Charts for 0.5"Hx1"W, 1"Hx2"W, 2"Hx2"W, 3"Hx2"W and 4"Hx4"W. Raw Gain was about the SAME, except (as expected) some loss with and about 1-2 dB LOSS for 4"Hx4"W. Front/Back Ratio was much better with 1"Hx2"W than 0.5"Hx1"W and progressively lower for 2"Hx2"W, 3"Hx2"W and 4"Hx4"W. Front/Rear Ratio was about the SAME with 1"Hx2"W and 0.5"Hx1"W and progressively lower for 2"Hx2"W, 3"Hx2"W and 4"Hx4"W. [Errata: Fixed earlier error in F/B for 0.5"Hx1"W.]
EDIT (10Jun2014): Also added 3"Hx2"W Grid Size....which nicely fits in-between plots for 2"Hx2"W and 4"Hx4"W. Plots for 1"Hx1"W and 2"Hx4"W are not included, since they were within a few tenths of a dB of 1"Hx2"W and 2"Hx2"W respectively. The spacing of the HORIZONTAL wires primarily determine performance, since Vertical Wires have only minimal effect on Horizontally Polarized signals.
Date(s): 3 Dec 2011. Album by holl_ands. 1 - 61 of 61 Total. 5229 Visits.
enlarge 154KB, 668x1024 1 Old CM4228 8-Bay Bowtie w Screen Reflector 3D View
enlarge 337KB, 1024x847 2 Old CM4228 8-Bay Bowtie w Screen Reflector Front View [1 big box = 5-inches]
enlarge 64KB, 255x1024 3 Old CM4228 8-Bay Bowtie w Screen Reflector Top View [1 big box = 5-inches]
enlarge 153KB, 1152x584 4 Old CM4228 8-Bay Bowtie w Screen Reflector UHF Raw Gain
enlarge 172KB, 1152x584 5 Old CM4228 8-Bay Bowtie w Screen Reflector UHF SWR (300-ohms) Under 2.4
enlarge 148KB, 1152x584 6 Old CM4228 8-Bay Bowtie w Screen Reflector UHF Impedance
enlarge 187KB, 1152x678 7 Old CM4228 8-Bay Bowtie w Screen Reflector Raw Gain vs Bowtie Tine Separation ANOMALOUS RESULTS at 470 MHz
enlarge 222KB, 1152x678 8 Old CM4228 8-Bay Bowtie w Screen Reflector SWR (300-ohms) vs Bowtie Tine Separation POSSIBLY ANOMALOUS RESULTS at 470 MHz
enlarge 252KB, 1152x678 9 Old CM4228 8-Bay Bowtie w Screen Reflector Impedance vs Bowtie Tine Separation POSSIBLY ANOMALOUS RESULTS at 470 MHz
enlarge 183KB, 1152x678 10 Old CM4228 8-Bay Bowtie w Screen Reflector Raw Gain vs Bowtie Forward Sweep ANOMALOUS BLIP at 470 MHz
enlarge 218KB, 1152x678 11 Old CM4228 8-Bay Bowtie w Screen Reflector SWR (300-ohms) vs Bowtie Forward Sweep NORMAL RESULTS at 470 MHz
enlarge 243KB, 1152x678 12 Old CM4228 8-Bay Bowtie w Screen Reflector Impedance vs Bowtie Forward Sweep ANOMALOUS BLIP at 470 MHz
enlarge 302KB, 1024x1024 13 Old CM4228 8-Bay Bowtie w Screen Reflector Azimuthal Pattern for 470 MHz
enlarge 299KB, 1024x1024 14 Old CM4228 8-Bay Bowtie w Screen Reflector Azimuthal Pattern for 530 MHz
enlarge 301KB, 1024x1024 15 Old CM4228 8-Bay Bowtie w Screen Reflector Azimuthal Pattern for 590 MHz
enlarge 303KB, 1024x1024 16 Old CM4228 8-Bay Bowtie w Screen Reflector Azimuthal Pattern for 650 MHz
enlarge 307KB, 1024x1024 17 Old CM4228 8-Bay Bowtie w Screen Reflector Azimuthal Pattern for 698 MHz
enlarge 303KB, 1024x1024 18 Old CM4228 8-Bay Bowtie w Screen Reflector Azimuthal Pattern for 758 MHz
enlarge 304KB, 1024x1024 19 Old CM4228 8-Bay Bowtie w Screen Reflector Azimuthal Pattern for 806 MHz
enlarge 71KB, 314x1024 20 Old CM4228 8-Bay Bowtie w Screen Reflector Side View [1 big box = 5-inches]
enlarge 116KB, 791x1024 21 Old CM4228 8-Bay Bowtie w Screen Reflector 4nec2 File (For UHF Runs ONLY).
enlarge 143KB, 1152x584 22 Old CM4228 8-Bay Bowtie w Screen Reflector Hi-VHF Raw Gain (Gain Hole on Ch11)
enlarge 187KB, 1152x584 23 Old CM4228 8-Bay Bowtie w Screen Reflector Hi-VHF SWR (300-ohms) IS EXCESSIVE
enlarge 158KB, 1152x584 24 Old CM4228 8-Bay Bowtie w Screen Reflector Hi-VHF Impedance
enlarge 307KB, 1024x1024 25 Old CM4228 8-Bay Bowtie w Screen Reflector Azimuthal Pattern for 174 MHz
enlarge 305KB, 1024x1024 26 Old CM4228 8-Bay Bowtie w Screen Reflector Azimuthal Pattern for 198 MHz
enlarge 305KB, 1024x1024 27 Old CM4228 8-Bay Bowtie w Screen Reflector Azimuthal Pattern for 201 MHz Gain Hole on Ch11
enlarge 304KB, 1024x1024 28 Old CM4228 8-Bay Bowtie w Screen Reflector Azimuthal Pattern for 204 MHz
enlarge 309KB, 1024x1024 29 Old CM4228 8-Bay Bowtie w Screen Reflector Azimuthal Pattern for 216 MHz
enlarge 118KB, 791x1024 30 Old CM4228 8-Bay Bowtie w Screen Reflector 4nec2 File (For Hi-VHF Runs ONLY).
enlarge 186KB, 763x1024 31 Old CM4228 8-Bay Bowtie w Screen Reflector Horizontal Harness Moved to FRONT 3D View
enlarge 345KB, 1024x847 32 Old CM4228 8-Bay Bowtie w Screen Reflector Horizontal Harness Moved to FRONT Front View [1 big box = 5-inches]
enlarge 75KB, 300x1024 33 Old CM4228 8-Bay Bowtie w Screen Reflector Horizontal Harness Moved to FRONT Top View [1 big box = 2.5-inches]
enlarge 162KB, 1152x584 34 Old CM4228 8-Bay Bowtie w Screen Reflector Horizontal Harness Moved to FRONT UHF Raw Gain Lost 1 dB on 470 MHz
enlarge 170KB, 1152x584 35 Old CM4228 8-Bay Bowtie w Screen Reflector Horizontal Harness Moved to FRONT UHF SWR (300-ohms) Under 2.4, with lower SWR just above 470 MHz
enlarge 147KB, 1152x584 36 Old CM4228 8-Bay Bowtie w Screen Reflector Horizontal Harness Moved to FRONT UHF Impedance
enlarge 301KB, 1024x1024 37 Old CM4228 8-Bay Bowtie w Screen Reflector Horizontal Harness Moved to FRONT Azimuthal Pattern at 470 MHz
enlarge 300KB, 1024x1024 38 Old CM4228 8-Bay Bowtie w Screen Reflector Horizontal Harness Moved to FRONT Azimuthal Pattern at 590 MHz
enlarge 306KB, 1024x1024 39 Old CM4228 8-Bay Bowtie w Screen Reflector Horizontal Harness Moved to FRONT Azimuthal Pattern at 698 MHz
enlarge 303KB, 1024x1024 40 Old CM4228 8-Bay Bowtie w Screen Reflector Horizontal Harness Moved to FRONT Azimuthal Pattern at 758 MHz
enlarge 303KB, 1024x1024 41 Old CM4228 8-Bay Bowtie w Screen Reflector Horizontal Harness Moved to FRONT Azimuthal Pattern at 806 MHz
enlarge 120KB, 791x1024 42 Old CM4228 8-Bay Bowtie w Screen Reflector Horizontal Harness Moved to FRONT 4nec2 File (For UHF Runs ONLY).
enlarge 151KB, 1152x584 43 Old CM4228 8-Bay Bowtie w Screen Reflector Horizontal Harness Moved to FRONT Hi-VHF Raw Gain - Ch11 Gain Hole
enlarge 203KB, 1152x584 44 Old CM4228 8-Bay Bowtie w Screen Reflector Horizontal Harness Moved to FRONT Hi-VHF SWR (300-ohms) IS EXCESSIVE
enlarge 138KB, 1152x584 45 Old CM4228 8-Bay Bowtie w Screen Reflector Horizontal Harness Moved to FRONT Hi-VHF Impedance - Very Low Resistance
enlarge 308KB, 1024x1024 46 Old CM4228 8-Bay Bowtie w Screen Reflector Horizontal Harness Moved to FRONT Azimuthal Pattern at 174 MHz
enlarge 307KB, 1024x1024 47 Old CM4228 8-Bay Bowtie w Screen Reflector Horizontal Harness Moved to FRONT Azimuthal Pattern at 198 MHz
enlarge 308KB, 1024x1024 48 Old CM4228 8-Bay Bowtie w Screen Reflector Horizontal Harness Moved to FRONT Azimuthal Pattern at 199.5 MHz
enlarge 309KB, 1024x1024 49 Old CM4228 8-Bay Bowtie w Screen Reflector Horizontal Harness Moved to FRONT Azimuthal Pattern at 204 MHz
enlarge 308KB, 1024x1024 50 Old CM4228 8-Bay Bowtie w Screen Reflector Horizontal Harness Moved to FRONT Azimuthal Pattern at 216 MHz
enlarge 95KB, 1024x966 51 Old CM4228 8-Bay Bowtie w Screen Reflector Horizontal Harness Moved to FRONT 3D Detail View of Harness
enlarge 248KB, 1024x696 52 Old CM4228 8-Bay Bowtie w Screen Reflector where Reflector = 36-in H x 40-in W UHF Raw Gain: Compare Various Grid Sizes
enlarge 272KB, 1024x696 53 Old CM4228 8-Bay Bowtie w Screen Reflector where Reflector = 36-in H x 40-in W UHF F/R & F/B: Compare Various Grid Sizes
enlarge 80KB, 258x1024 54 Old CM4228 8-Bay Bowtie w Screen Reflector Horizontal Harness Moved to FRONT Side View [1 big box = 5-inches]
enlarge 120KB, 791x1024 55 Old CM4228 8-Bay Bowtie w Screen Reflector Horizontal Harness Moved to FRONT 4nec2 File (For Hi-VHF Runs ONLY).
enlarge 348KB, 791x1024 56 Old CM4228 8-Bay Bowtie w Screen Reflector Horizontal Harness Moved to FRONT 4nec2 File (For UHF Runs ONLY). If use Grid = 0.5-in H x 1-in W
enlarge 76KB, 791x1024 57 Old CM4228 8-Bay Bowtie w Screen Reflector Horizontal Harness Moved to FRONT 4nec2 File (For UHF Runs ONLY). If use Grid = 2-in H x 2-in W
enlarge 70KB, 791x1024 58 Old CM4228 8-Bay Bowtie w Screen Reflector Horizontal Harness Moved to FRONT 4nec2 File (For UHF Runs ONLY). If use Grid = 2-in H x 3.077-in W
enlarge 58KB, 791x1024 59 Old CM4228 8-Bay Bowtie w Screen Reflector Horizontal Harness Moved to FRONT 4nec2 File (For UHF Runs ONLY). If use Grid = 2-in H x 4-in W
enlarge 64KB, 791x1024 60 Old CM4228 8-Bay Bowtie w Screen Reflector Horizontal Harness Moved to FRONT 4nec2 File (For UHF Runs ONLY). If use Grid = 3-in H x 2-in W
enlarge 48KB, 791x1024 61 Old CM4228 8-Bay Bowtie w Screen Reflector Horizontal Harness Moved to FRONT 4nec2 File (For UHF Runs ONLY). If use Grid = 4-in H x 4-in W
