UHF (New) CM4221HD 4-Bay with 16 Reflector Rods (23.6-in Wide, Sep=4.25-in) modeled using 4nec2.
UHF Raw Gain=11.2-14.8 dBi. UHF SWR(300) under 2.1. UHF F/B Ratio=19-33 dB and UHF F/R Ratio=15-18 dB.
NOTE: CM4221HD's PCB Balun ATTENUATES VHF, however if REPLACE Balun then: Hi-VHF Raw Gain=3-6.6 dBi (FORWARD), but HIGHER Hi-VHF Raw Gain=7.7-5.0 dBi (TOWARDS REAR!). Hi-VHF SWR(300)=EXCESSIVE, esp. on lower Hi-VHF channels.
CM4221HD measurements per fol. smpowell55 posts: http://www.digitalhome.ca/forum/showthread.php?p=863127 http://www.digitalhome.ca/forum/showthread.php?p=863559
BowLength = 7.9-in, Inner-Inner Bowtie Spacing = 9.84-in, Outer-Inner Bowtie Spacing = 8.46-in, Tine Separation = 3.94-in. Feedline Separation = 1.18-in, with 0.8-in at Crossover (2" from Outer Bowtie). 16 Rod Reflectors: 23.6" Long with 1.93" Spacings for Total Height = 30-in. Separation from Bowties = 4.25-in.
It is presumed that anyone interested enough to view this webpage will implement the "Hacked Balun" modifications per photo in fol. rabbit73 post (flip over the Feedlines going into the Balun plus an additional offset): http://www.digitalhome.ca/forum/showthread.php?p=1167870
Although NEW, the CM4221HD is still optimized for the OLD UHF Band (up thru Ch69), wasting the Max Gain peak on channels that are no longer available for DTV. UHF Raw Gain is about the same as older CM4221 with improved UHF SWR on the lower channels....and Hi-VHF Raw Gain & SWR, such as it is, has been degraded....
Super-Sized-4-Bays have better Gain on New UHF Band (up thru Ch51) and don't have a Hi-VHF Gain Reversal problem.
EDIT (30Mar2013): Added (Slides 7-12) MOSTLY NORMAL plots versus Bowtie Tine Separation and Bowtie Forward Sweep, although at more than 1-1/2 inch increase in Tine Separation, a significant Gain & SWR Glitch was found, which could frustrate finding an "Optimum" set of dimensions. This may or may not be a 4nec2 Modeling anomaly, and might not be inherent in CM4221HD design.
Note that in 8-Bay Bowtie Antennas significant Gain & SWR glitches were found with very small (under 0.5-in) changes in Tine Separation and Bowtie Forward Sweep from "As Built" dimensions.
EDIT (26Oct2013): Investigated comment below. Segmentation in Feedline etc is as it should be. However, when investigating other Autoseg numbers other than 11, I found that Autoseg(15) and Autoseg(21) found "sharp angle warnings" and an AGT error resulting in 1 db lower Gain. Since the Autoseg(11) did not find any "sharp angle warnings" and looks good, I'm sticking with it.
EDIT (26Oct2013): Added Rmax Parameter Sweep Charts (Reflector Rod Length = 2*Rmax) at 3 freqs. Rmax can only be increased from 11.8 to 12.8-in before there is Gain LOSS on 698 MHz. This mod would only result in a very minor (0.05 to 0.3 dB) improvement in overall Gain.
EDIT (3Apr2017): Added Elevation Angle Pattern Charts, showing NULLS at about 30-deg.
Date(s): 5 Oct 2011. Album by holl_ands. 1 - 36 of 36 Total. 9317 Visits.
enlarge 151KB, 609x1024 1 New CM4221HD 4-Bay w 16 Reflector Rods 3D View
enlarge 303KB, 896x1024 2 New CM4221HD 4-Bay w 16 Reflector Rods Front View [1 big box = 2.5-inches]
enlarge 107KB, 321x1024 3 New CM4221HD 4-Bay w 16 Reflector Rods Side View [1 big box = 2.5-inches]
enlarge 171KB, 1152x584 4 New CM4221HD 4-Bay w 16 Reflector Rods UHF Raw Gain, F/B & F/R Ratios
enlarge 190KB, 1152x584 5 New CM4221HD 4-Bay w 16 Reflector Rods UHFSWR (300-ohms) under 2.1
enlarge 154KB, 1152x584 6 New CM4221HD 4-Bay w 16 Reflector Rods UHF Impedance
enlarge 199KB, 1152x678 7 New CM4221HD w 16 Reflector Rods Raw Gain vs Bowtie Tine Separation, 470 MHz NORMAL, but ANOMALIES 1.5-in away
enlarge 204KB, 1152x678 8 New CM4221HD w 16 Reflector Rods SWR (300-ohms) vs Bowtie Tine Separation NORMAL, but ANOMALIES 1-1/2 inches away
enlarge 245KB, 1152x678 9 New CM4221HD w 16 Reflector Rods Impedance vs Bowtie Tine Separation NORMAL, but ANOMALIES 1-1/2 inches away
enlarge 189KB, 1152x678 10 New CM4221HD w 16 Reflector Rods Raw Gain vs Bowtie Forward Sweep NORMAL RESULTS at 470 MHz
enlarge 201KB, 1152x678 11 New CM4221HD w 16 Reflector Rods SWR (300-ohms) vs Bowtie Forward Sweep NORMAL RESULTS at 470 MHz
enlarge 241KB, 1152x678 12 New CM4221HD w 16 Reflector Rods Impedance vs Bowtie Forward Sweep NORMAL RESULTS at 470 MHz
enlarge 316KB, 1024x1024 13 New CM4221HD 4-Bay w 16 Reflector Rods Azimuthal Pattern at 470 MHz
enlarge 319KB, 1024x1024 14 New CM4221HD 4-Bay w 16 Reflector Rods Azimuthal Pattern at 590 MHz
enlarge 318KB, 1024x1024 15 New CM4221HD 4-Bay w 16 Reflector Rods Azimuthal Pattern at 698 MHz
enlarge 318KB, 1024x1024 16 New CM4221HD 4-Bay w 16 Reflector Rods Azimuthal Pattern at 758 MHz
enlarge 315KB, 1024x1024 17 New CM4221HD 4-Bay w 16 Reflector Rods Azimuthal Pattern at 806 MHz
enlarge 106KB, 394x1024 18 New CM4221HD 4-Bay w 16 Reflector Rods Top View [1 big box = 2.5-inches]
enlarge 156KB, 1152x584 19 New CM4221HD 4-Bay w 16 Reflector Rods Hi-VHF Raw Gain FORWARD
enlarge 147KB, 1152x584 20 New CM4221HD 4-Bay w 16 Reflector Rods Hi-VHF Raw Gain, F/B & F/R Ratios HIGHER to REAR
enlarge 180KB, 1152x584 21 New CM4221HD 4-Bay w 16 Reflector Rods Hi-VHF SWR (300-ohms) is EXCESSIVE
enlarge 318KB, 1024x1024 22 New CM4221HD 4-Bay w 16 Reflector Rods Azimuthal Pattern at 174 MHz
enlarge 319KB, 1024x1024 23 New CM4221HD 4-Bay w 16 Reflector Rods Azimuthal Pattern at 186 MHz
enlarge 320KB, 1024x1024 24 New CM4221HD 4-Bay w 16 Reflector Rods Azimuthal Pattern at 198 MHz
enlarge 320KB, 1024x1024 25 New CM4221HD 4-Bay w 16 Reflector Rods Azimuthal Pattern at 207 MHz
enlarge 317KB, 1024x1024 26 New CM4221HD 4-Bay w 16 Reflector Rods Azimuthal Pattern at 216 MHz
enlarge 42KB, 791x1024 27 New CM4221HD 4-Bay w 16 Reflector Rods 4nec2 File
enlarge 313KB, 1024x1024 28 New CM4221HD 4-Bay w 16 Reflector Rods Elevation Pattern at 470 MHz
enlarge 314KB, 1024x1024 29 New CM4221HD 4-Bay w 16 Reflector Rods Elevation Pattern at 530 MHz
enlarge 313KB, 1024x1024 30 New CM4221HD 4-Bay w 16 Reflector Rods Elevation Pattern at 590 MHz
enlarge 312KB, 1024x1024 31 New CM4221HD 4-Bay w 16 Reflector Rods Elevation Pattern at 650 MHz
enlarge 313KB, 1024x1024 32 New CM4221HD 4-Bay w 16 Reflector Rods Elevation Pattern at 698 MHz
enlarge 317KB, 1024x1024 33 New CM4221HD 4-Bay w 16 Reflector Rods Elevation Pattern at 806 MHz
enlarge 228KB, 1152x558 34 New CM4221HD 4-Bay w 16 Reflector Rods Rmax Parameter Sweep at 470 MHz [Reflector Rod Length = 2*Rmax]
Gain increases 0.4 dB if Rmax 11.8 to 15.8-in.
enlarge 226KB, 1152x551 35 New CM4221HD 4-Bay w 16 Reflector Rods Rmax Parameter Sweep at 584 MHz [Reflector Rod Length = 2*Rmax]
Gain increases 0.5 dB if Rmax from 11.8 to 14.8-in.
enlarge 223KB, 1152x546 36 New CM4221HD 4-Bay w 16 Reflector Rods Rmax Parameter Sweep at 698 MHz [Reflector Rod Length = 2*Rmax]
Gain increases 0.05 dB if Rmax from 11.8 to 12.8-in, however for larger Rmax, Gain is REDUCED.
Segmentation is CORRECT. I used 4nec2's Autosegmentation feature. As shown in the posted 4nec2 File, the longest sections in the Feedline are 7 segments, medium length sections 3 segments and the short segments in the Crossover "Hop" are just 1 segment. - holl_ands, Fri, 2 Aug 2019 12:15PM
The file provided has single segments for the feedline, which results in excessively good performance; when changed to normal, the nice performance is gone...
However, I corrected that and changed a few things, now I have something better than the data here shows. - ohai, Sun, 11 Aug 2013 11:53AM
