New CM4228HD 8-Bay Bowtie Antenna (If NO Relector for Bi-Directional pattern) analyzed using 4nec2. Measurements taken directly from a newly delivered antenna.
Investigates UHF and Hi-VHF performance if a user decides to remove the Reflector. A supporting structure would then need to be provided, such as using PVC pipes.
UHF SWR is Good, but Raw Gain is only 6 dBi on Ch14, climbing to about 11 dBi just below Ch51. Hi-VHF SWR is Excessive, except above Ch10. Hi-VHF Gain is Good, except on Ch10.
NOTE: The Autosegment feature of 4nec2 was used to determine how many wire segments to use when modeling each wire element. The choice of Autosegment=11 was very critical in getting the CM-4228HD Gain and SWR calculations to work AT ALL. And small changes to Autosegment resulted in large changes in Hi-VHF Gain & SWR....so Hi-VHF might not be all that accurate.
Date(s): 28 Aug 2010. Album by holl_ands. 1 - 24 of 24 Total. 4528 Visits.
enlarge 106KB, 784x1024 1 New CM4228HD - As Shipped, if REMOVE Reflectors. 3D View
enlarge 273KB, 1024x734 2 New CM4228HD - As Shipped, if REMOVE Reflectors. Front View [1 small square = 0.5-inch]
enlarge 79KB, 256x1024 3 New CM4228HD - As Shipped, if REMOVE Reflectors. Top View [1 small square = 0.5-inch]
enlarge 133KB, 1024x648 4 New CM4228HD - As Shipped, if REMOVE Reflectors. UHF Raw Gain reaches Max of about 12 dBi on Ch51. Significant Gain Loss below Ch26. Only 6 dBi on Ch14.
enlarge 152KB, 1024x648 5 New CM4228HD - As Shipped, if REMOVE Reflectors. UHF SWR (300-ohm) is Very Good, except for rise on Ch14.
enlarge 145KB, 1024x648 6 New CM4228HD - As Shipped, if REMOVE Reflectors. UHF Impedance
enlarge 310KB, 1024x1024 7 New CM4228HD - As Shipped, if REMOVE Reflectors. UHF Azimuthal Pattern at 470 MHz.
enlarge 306KB, 1024x1024 8 New CM4228HD - As Shipped, if REMOVE Reflectors. UHF Azimuthal Pattern at 518MHz.
enlarge 306KB, 1024x1024 9 New CM4228HD - As Shipped, if REMOVE Reflectors. UHF Azimuthal Pattern at 590 MHz.
enlarge 308KB, 1024x1024 10 New CM4228HD - As Shipped, if REMOVE Reflectors. UHF Azimuthal Pattern at 698 MHz.
enlarge 307KB, 1024x1024 11 New CM4228HD - As Shipped, if REMOVE Reflectors. UHF Azimuthal Pattern at 758 MHz.
enlarge 308KB, 1024x1024 12 New CM4228HD - As Shipped, if REMOVE Reflectors. UHF Azimuthal Pattern at 806 MHz.
enlarge 133KB, 1024x648 13 New CM4228HD - As Shipped, if REMOVE Reflectors. Hi-VHF Raw Gain Good 3-4 dBi, except drops to 0 dBi on Ch10.
enlarge 172KB, 1024x648 14 New CM4228HD - As Shipped, if REMOVE Reflectors. UHF SWR (300-ohm) Excessive except Good above Ch10.
enlarge 150KB, 1024x648 15 New CM4228HD - As Shipped, if REMOVE Reflectors. UHF Impedance.
enlarge 310KB, 1024x1024 16 New CM4228HD - As Shipped, if REMOVE Reflectors. Hi-VHF Azimuthal Pattern at 174 MHz.
enlarge 312KB, 1024x1024 17 New CM4228HD - As Shipped, if REMOVE Reflectors. Hi-VHF Azimuthal Pattern at 186 MHz.
enlarge 312KB, 1024x1024 18 New CM4228HD - As Shipped, if REMOVE Reflectors. Hi-VHF Azimuthal Pattern at 198 MHz.
enlarge 305KB, 1024x1024 19 New CM4228HD - As Shipped, if REMOVE Reflectors. Hi-VHF Azimuthal Pattern at 203 MHz. Ch10 MINIMUM Gain point (only 0 dBi)
enlarge 307KB, 1024x1024 20 New CM4228HD - As Shipped, if REMOVE Reflectors. Hi-VHF Azimuthal Pattern at 207 MHz.
enlarge 308KB, 1024x1024 21 New CM4228HD - As Shipped, if REMOVE Reflectors. Hi-VHF Azimuthal Pattern at 216 MHz.
enlarge 83KB, 303x1024 22 New CM4228HD - As Shipped, if REMOVE Reflectors. Side View [1 small square = 0.5-inch]
enlarge 40KB, 791x1024 23 New CM4228HD - As Shipped, if REMOVE Reflectors. 4nec2 File - For UHF Band ONLY
enlarge 39KB, 791x1024 24 New CM4228HD - As Shipped, if REMOVE Reflectors. 4nec2 File - For Hi-VHF Band ONLY
Thanks for the analysis. I have been contemplating the removal of my CM-4228HD reflector so I can receive UHF and VHF from both the Los Angeles and San Diego Transmitters (180 degrees opposite direction from my home.) Currently I point my CM-4228HD toward Mt. Wilson 91.8 miles away (6,000 ft elevation). I receive approx 50 channels from LA and 5-10 from San Diego. I'm thinking I can remove the reflector and receive the San Diego stations better (currently marginal reception through back of reflector for San Diego channels). All channels (both directions) are 2-edge and scattered. If removing the reflector doesn't do the trick, then I'll try another CM-4228HD back-to-back on the same mast. No transmission frequency conflicts exist between LA and San Diego on any channel I care to watch. I will preamplify LA channels with approx +20dB gain (UHF) and a separate preamp for San Diego at approx. 14dB gain in order to equalize the signal level in my Channel Master DVR+ tuner. Any other suggestions? Gary Nelson Carlsbad, Ca. 92009 760-613-1695 cell - Gary Nelson, Wed, 23 Apr 2014 3:12PM
