CM4228HD with RF Combiner Modification (RCM) analyzed using 4nec2 . The Horizontal Interconnect Harness between the two 4-Bays is replaced by a Balun at the center drive point of each 4-Bay, which are summed using an RF Combiner Module.
UHF Raw Gain climbs to about 17 dBi on highest Ch69 and lowest four channels (Ch14-17) are above 13 dBi. UHF SWR is Very Good, although rises to 3.5 on lowest Ch14. Hi-VHF Raw Gain is quite HIGH and SWR is Very Good except below Ch10.
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.]
EDIT (29Mar2013): Added (Slides 7-12) 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 CM4228HD design. There's NO WAY Whisker movements of a couple thousandths of an inch result in BIG Gain & SWR changes.
Added (Slide 30) NORMAL Small Perturbation Test Results showing Raw Gain is within +/- 0.5 dB when Bowtie Tine Separation and Bowtie Forward Sweep are Randomly Perturbed by up to +/- 0.25-in, using EXCEL's 0.0001*RANDBETWEEN(-2500,2500) function to generate variables. Indicates Raw Gain at 470 MHz is probably closer to 14.0 dBi than 13.2 dBi shown in "unperturbed" 4nec2 Model.
Date(s): 28 Aug 2010. Album by holl_ands. 1 - 31 of 31 Total. 6776 Visits.
enlarge 196KB, 828x1024 1 New CM4228HD - With RF Combiner Mod 3D View
enlarge 253KB, 1024x720 2 New CM4228HD - With RF Combiner Mod Front View [1 small box = 1-inch]
enlarge 71KB, 305x1024 3 New CM4228HD - With RF Combiner Mod Top View [1 small box = 1-inch]
enlarge 151KB, 1024x648 4 New CM4228HD - With RF Combiner Mod UHF Raw Gain Climbs to about 17 dBi on highest Ch69. Lowest four channels (Ch14-17) are above 13 dBi.
enlarge 161KB, 1024x648 5 New CM4228HD - With RF Combiner Mod UHF SWR (300-ohm) Very Good, except rises to 3.6 on lowest Ch14.
enlarge 134KB, 1024x648 6 New CM4228HD - With RF Combiner Mod UHF Impedance
enlarge 182KB, 1152x678 7 New CM4228HD - With RF Combiner Mod Raw Gain vs Bowtie Tine Separation ANOMALOUS RESULTS at 470 MHz
enlarge 214KB, 1152x678 8 New CM4228HD - With RF Combiner Mod SWR (300-ohms) vs Bowtie Tine Separation ANOMALOUS RESULTS at 470 MHz
enlarge 252KB, 1152x678 9 New CM4228HD - With RF Combiner Mod Impedance vs Bowtie Tine Separation ANOMALOUS RESULTS at 470 MHz
enlarge 194KB, 1152x678 10 New CM4228HD - With RF Combiner Mod Raw Gain vs Bowtie Forward Sweep ANOMALOUS RESULTS at 470 MHz
enlarge 215KB, 1152x678 11 New CM4228HD - With RF Combiner Mod SWR (300-ohms) vs Bowtie Forward Sweep ANOMALOUS RESULTS at 470 MHz
enlarge 238KB, 1152x678 12 New CM4228HD - With RF Combiner Mod Impedance vs Bowtie Forward Sweep ANOMALOUS RESULTS at 470 MHz
enlarge 304KB, 1024x1024 13 New CM4228HD - With RF Combiner Mod UHF Azimuthal Pattern at 470 MHz
enlarge 309KB, 1024x1024 14 New CM4228HD - With RF Combiner Mod UHF Azimuthal Pattern at 590 MHz
enlarge 309KB, 1024x1024 15 New CM4228HD - With RF Combiner Mod UHF Azimuthal Pattern at 698 MHz
enlarge 308KB, 1024x1024 16 New CM4228HD - With RF Combiner Mod UHF Azimuthal Pattern at 758 MHz
enlarge 310KB, 1024x1024 17 New CM4228HD - With RF Combiner Mod UHF Azimuthal Pattern at 806 MHz
enlarge 84KB, 366x1024 18 New CM4228HD - With RF Combiner Mod Side View [1 small box = 1-inch]
enlarge 133KB, 1024x648 19 New CM4228HD - With RF Combiner Mod Hi-VHF Raw Gain High Gain - Exceeds 8.5 dBi on most Hi-VHF channels.
enlarge 172KB, 1024x648 20 New CM4228HD - With RF Combiner Mod Hi-VHF SWR (300-ohm) Good on Ch10 and above, Excessive on lower channels.
enlarge 148KB, 1024x648 21 New CM4228HD - With RF Combiner Mod Hi-VHF Impedance
enlarge 308KB, 1024x1024 22 New CM4228HD - With RF Combiner Mod Hi-VHF Azimuthal Pattern at 174 MHz
enlarge 310KB, 1024x1024 23 New CM4228HD - With RF Combiner Mod Hi-VHF Azimuthal Pattern at 177 MHz Minimum Gain point still provides 7.14 dBi.
enlarge 309KB, 1024x1024 24 New CM4228HD - With RF Combiner Mod Hi-VHF Azimuthal Pattern at 186 MHz
enlarge 308KB, 1024x1024 25 New CM4228HD - With RF Combiner Mod Hi-VHF Azimuthal Pattern at 198 MHz
enlarge 308KB, 1024x1024 26 New CM4228HD - With RF Combiner Mod Hi-VHF Azimuthal Pattern at 204 MHz
enlarge 309KB, 1024x1024 27 New CM4228HD - With RF Combiner Mod Hi-VHF Azimuthal Pattern at 216 MHz
enlarge 46KB, 791x1024 28 New CM4228HD - With RF Combiner Mod 4nec2 File - Segmented for UHF Runs
enlarge 46KB, 791x1024 29 New CM4228HD - With RF Combiner Mod 4nec2 File - Segmented for Hi-VHF Runs
enlarge 248KB, 1024x696 30 New CM4228HD - With RF Combiner Mod Perturbation Test Results Raw Gain is within +/- 0.5 dB when Bowtie Tine Separation & Bowtie Forward Sweep are Randomly Perturbed up to +/- 0.25-in.
enlarge 47KB, 791x1024 31 New CM4228HD - With RF Combiner Mod 4nec2 File - Example for Perturbation Test
