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holl_ands | Home > Stacked Antennas > Horizontally Stacked UHF Antennas > Browse:Horiz-Stack 2xFF6 + VDAR + HHHHoriz-Stack 2xFF4 + DAR + HHHHoriz-Stack 2xFF4 + DoubleAng Refl - RFCHoriz-Stack FF4+DAR Angled Against WallHoriz-Stacked CM4221HD's - RF CombinerHoriz-Stck 2xCM4221HD Hacked - NULL BEAMHoriz-Stack UHF Hourglass-Loop - NO ReflHoriz-Stack UHF Hourglass-Loop + 15RR
Horiz-Stck 2xCM4221HD Hacked - NULL BEAM UHF Horizontally Stacked 2xCM4221HD (Hacked), connected Out-Of-Phase for a NULL on-axis, with 2 or more Beams on either side, described on HDTVPrimer as the "Two-Antenna Trick": http://www.hdtvprimer.com/antennas/ganging.html Since the original CM4221's are no longer available, the replacement CM4221HD was analyzed. As shown in the charts for five different Horizontal Stacking Distances, a fairly deep Null can be formed directly on-axis, with Narrow Beams formed on either side of the Null.  For some combinations of Frequency and Stacking Distance, an additional pair of usable Beams may or may not be formed at angles even further away. BTW: Horiz. Stacking Distance is between the Centers of each 4-Bay. Note that for this CM4221HD example (which has a fairly wide Beamwidth), the third pair of Beams has very little usable Gain.  Different Antennas will likely exhibit different performance. The Chart at the bottom plots the Angle between the forward Null and the Adjacent Beams, as well as the Secondary Beams (if usable Gain) versus the Horizontal Stacking Distance. Using CM4221HD's, (without modifications), the Reflector Rods limit how close the 4-Bays can be mounted.  With modifications, the Null-to-Beam Angle could be increased a bit more. To receive a weak station separated by a very small Angle from a strong local station, the two Antennas need to have a fairly large Stacking Distance...far more than would be feasible mounted on a typical Rotator, which is limited in it's ability to tolerate strong twisting in the wind.  If using fixed locations for the two Antennas, their location(s) would need to be carefully adjusted while monitoring how well the strong local station is nulled out.  In similar Antenna sidelobe nulling adjustments, I had to add a Variable RF Attenuator to reduce the tuner signals levels closer to threshold to "see" the null. Per the Azimuthal Pattern Charts, strong signals should be attenuated at least 10-15 dB relative to the weak desired signal.  Actual On-Air tests would need to be conducted to verify this prediction and see if even deeper Nulls are possible given "real world" inaccuracies in pointing the Array and matching the Antennas [doublecheck dimensions]. Date(s): 20 Dec 2013. Album by holl_ands. 1 - 76 of 76 Total. 2986 Visits.
enlarge 214KB, 1024x910 1 H-Stk CM4221HD NULL BEAM D = 24-in 3D View enlarge 264KB, 1024x737 2 H-Stk CM4221HD NULL BEAM D = 24-in Front View [1 large square = 12.5 inches] enlarge 125KB, 461x1024 3 H-Stk CM4221HD NULL BEAM D = 24-in Top View [1 large square = 12.5 inches] enlarge 179KB, 1152x714 4 H-Stk CM4221HD NULL BEAM D = 24-in UHF Raw Gain = 11.4 to 15.0 dBi for Azimuth = 71 & 109-deg enlarge 202KB, 1152x714 5 H-Stk CM4221HD NULL BEAM D = 24-in UHF SWR (300-ohms) Under 4.3 is a Bit High enlarge 257KB, 1152x714 6 H-Stk CM4221HD NULL BEAM D = 24-in UHF Impedance enlarge 304KB, 1024x1024 7 H-Stk CM4221HD NULL BEAM D = 24-in Azimuthal Pattern at 470 MHz enlarge 303KB, 1024x1024 8 H-Stk CM4221HD NULL BEAM D = 24-in Azimuthal Pattern at 530 MHz enlarge 303KB, 1024x1024 9 H-Stk CM4221HD NULL BEAM D = 24-in Azimuthal Pattern at 590 MHz enlarge 306KB, 1024x1024 10 H-Stk CM4221HD NULL BEAM D = 24-in Azimuthal Pattern at 650 MHz enlarge 306KB, 1024x1024 11 H-Stk CM4221HD NULL BEAM D = 24-in Azimuthal Pattern at 698 MHz enlarge 309KB, 1024x1024 12 H-Stk CM4221HD NULL BEAM D = 24-in Azimuthal Pattern at 758 MHz enlarge 309KB, 1024x1024 13 H-Stk CM4221HD NULL BEAM D = 24-in Azimuthal Pattern at 806 MHz enlarge 52KB, 791x1024 14 H-Stk CM4221HD NULL BEAM D = 24-in 4nec2 File enlarge 186KB, 630x1024 15 H-Stk CM4221HD NULL BEAM D = 24-in Side View [1 large square = 2.5 inches] enlarge 194KB, 949x1024 16 H-Stk CM4221HD NULL BEAM D = 40-in 3D View enlarge 251KB, 1152x599 17 H-Stk CM4221HD NULL BEAM D = 40-in Front View [1 large square = 12.5 inches] enlarge 112KB, 356x1024 18 H-Stk CM4221HD NULL BEAM D = 40-in Top View [1 large square = 12.5 inches] enlarge 92KB, 1152x387 19 H-Stk CM4221HD NULL BEAM D = 40-in UHF Raw Gain = 12.8 to 16.5 dBi for Azimuth = 77 & 103-deg enlarge 204KB, 1152x714 20 H-Stk CM4221HD NULL BEAM D = 40-in UHF SWR (300-ohms) Under 4.2 is a Bit High enlarge 261KB, 1152x714 21 H-Stk CM4221HD NULL BEAM D = 40-in UHF Impedance enlarge 307KB, 1024x1024 22 H-Stk CM4221HD NULL BEAM D = 40-in Azimuthal Pattern at 470 MHz enlarge 310KB, 1024x1024 23 H-Stk CM4221HD NULL BEAM D = 40-in Azimuthal Pattern at 530 MHz enlarge 318KB, 1024x1024 24 H-Stk CM4221HD NULL BEAM D = 40-in Azimuthal Pattern at 590 MHz enlarge 310KB, 1024x1024 25 H-Stk CM4221HD NULL BEAM D = 40-in Azimuthal Pattern at 650 MHz enlarge 311KB, 1024x1024 26 H-Stk CM4221HD NULL BEAM D = 40-in Azimuthal Pattern at 698 MHz enlarge 311KB, 1024x1024 27 H-Stk CM4221HD NULL BEAM D = 40-in Azimuthal Pattern at 758 MHz enlarge 314KB, 1024x1024 28 H-Stk CM4221HD NULL BEAM D = 40-in Azimuthal Pattern at 806 MHz enlarge 52KB, 791x1024 29 H-Stk CM4221HD NULL BEAM D = 40-in 4nec2 File enlarge 191KB, 642x1024 30 H-Stk CM4221HD NULL BEAM D = 40-in Side View [1 large square = 2.5 inches] enlarge 130KB, 751x1024 31 H-Stk CM4221HD NULL BEAM D = 60-in 3D View enlarge 170KB, 1152x532 32 H-Stk CM4221HD NULL BEAM D = 60-in Front View [1 large square = 12.5 inches] enlarge 88KB, 341x1024 33 H-Stk CM4221HD NULL BEAM D = 60-in Top View [1 large square = 12.5 inches] enlarge 100KB, 1152x387 34 H-Stk CM4221HD NULL BEAM D = 60-in UHF Raw Gain = 13.3 to 17.1 dBi for Azimuth = 81 & 99-deg enlarge 211KB, 1152x714 35 H-Stk CM4221HD NULL BEAM D = 60-in UHF SWR (300-ohms) Under 4.2 enlarge 263KB, 1152x714 36 H-Stk CM4221HD NULL BEAM D = 60-in UHF Impedance enlarge 312KB, 1024x1024 37 H-Stk CM4221HD NULL BEAM D = 60-in Azimuthal Pattern at 470 MHz enlarge 313KB, 1024x1024 38 H-Stk CM4221HD NULL BEAM D = 60-in Azimuthal Pattern at 530 MHz enlarge 314KB, 1024x1024 39 H-Stk CM4221HD NULL BEAM D = 60-in Azimuthal Pattern at 590 MHz enlarge 315KB, 1024x1024 40 H-Stk CM4221HD NULL BEAM D = 60-in Azimuthal Pattern at 650 MHz enlarge 316KB, 1024x1024 41 H-Stk CM4221HD NULL BEAM D = 60-in Azimuthal Pattern at 698 MHz enlarge 318KB, 1024x1024 42 H-Stk CM4221HD NULL BEAM D = 60-in Azimuthal Pattern at 758 MHz enlarge 320KB, 1024x1024 43 H-Stk CM4221HD NULL BEAM D = 60-in Azimuthal Pattern at 806 MHz enlarge 52KB, 791x1024 44 H-Stk CM4221HD NULL BEAM D = 60-in 4nec2 File enlarge 189KB, 642x1024 45 H-Stk CM4221HD NULL BEAM D = 60-in Side View [1 large square = 2.5 inches] enlarge 147KB, 1024x916 46 H-Stk CM4221HD NULL BEAM D = 60-in 3D View enlarge 144KB, 1152x430 47 H-Stk CM4221HD NULL BEAM D = 80-in Front View [1 large square = 12.5 inches] enlarge 75KB, 274x1024 48 H-Stk CM4221HD NULL BEAM D = 80-in Top View [1 large square = 12.5 inches] enlarge 179KB, 1152x714 49 H-Stk CM4221HD NULL BEAM D = 80-in UHF Raw Gain = 13.6 to 17.1 dBi for Azimuth = 83 & 97-deg enlarge 214KB, 1152x714 50 H-Stk CM4221HD NULL BEAM D = 80-in UHF SWR (300-ohms) Under 4.2 enlarge 267KB, 1152x714 51 H-Stk CM4221HD NULL BEAM D = 80-in UHF Impedance enlarge 312KB, 1024x1024 52 H-Stk CM4221HD NULL BEAM D = 80-in Azimuthal Pattern at 470 MHz enlarge 316KB, 1024x1024 53 H-Stk CM4221HD NULL BEAM D = 80-in Azimuthal Pattern at 530 MHz enlarge 324KB, 1024x1024 54 H-Stk CM4221HD NULL BEAM D = 80-in Azimuthal Pattern at 590 MHz enlarge 324KB, 1024x1024 55 H-Stk CM4221HD NULL BEAM D = 80-in Azimuthal Pattern at 650 MHz enlarge 321KB, 1024x1024 56 H-Stk CM4221HD NULL BEAM D = 80-in Azimuthal Pattern at 698 MHz enlarge 322KB, 1024x1024 57 H-Stk CM4221HD NULL BEAM D = 80-in Azimuthal Pattern at 758 MHz enlarge 322KB, 1024x1024 58 H-Stk CM4221HD NULL BEAM D = 80-in Azimuthal Pattern at 806 MHz enlarge 52KB, 791x1024 59 H-Stk CM4221HD NULL BEAM D = 80-in 4nec2 File enlarge 189KB, 645x1024 60 H-Stk CM4221HD NULL BEAM D = 80-in Side View [1 large square = 2.5 inches] enlarge 117KB, 1024x996 61 H-Stk CM4221HD NULL BEAM D = 120-in 3D View enlarge 124KB, 1152x331 62 H-Stk CM4221HD NULL BEAM D = 120-in Front View [1 large square = 12.5 inches] enlarge 72KB, 223x1024 63 H-Stk CM4221HD NULL BEAM D = 120-in Top View [1 large square = 12.5 inches] enlarge 186KB, 1152x714 64 H-Stk CM4221HD NULL BEAM D = 120-in UHF Raw Gain = 14.1 to 15.4 to 14.7 dBi for Azimuth = 84 & 96-deg enlarge 212KB, 1152x714 65 H-Stk CM4221HD NULL BEAM D = 120-in UHF SWR (300-ohms) Under 4.1 enlarge 273KB, 1152x714 66 H-Stk CM4221HD NULL BEAM D = 120-in UHF Impedance enlarge 321KB, 1024x1024 67 H-Stk CM4221HD NULL BEAM D = 120-in Azimuthal Pattern at 470 MHz enlarge 323KB, 1024x1024 68 H-Stk CM4221HD NULL BEAM D = 120-in Azimuthal Pattern at 530 MHz enlarge 330KB, 1024x1024 69 H-Stk CM4221HD NULL BEAM D = 120-in Azimuthal Pattern at 590 MHz enlarge 326KB, 1024x1024 70 H-Stk CM4221HD NULL BEAM D = 120-in Azimuthal Pattern at 650 MHz enlarge 328KB, 1024x1024 71 H-Stk CM4221HD NULL BEAM D = 120-in Azimuthal Pattern at 698 MHz enlarge 333KB, 1024x1024 72 H-Stk CM4221HD NULL BEAM D = 120-in Azimuthal Pattern at 758 MHz enlarge 330KB, 1024x1024 73 H-Stk CM4221HD NULL BEAM D = 120-in Azimuthal Pattern at 806 MHz enlarge 52KB, 791x1024 74 H-Stk CM4221HD NULL BEAM D = 120-in 4nec2 File enlarge 191KB, 646x1024 75 H-Stk CM4221HD NULL BEAM D = 120-in Side View [1 large square = 2.5 inches] enlarge 150KB, 1024x743 76 Horiz-Stack CM4221HD NULL BEAM Angle Between Null and Beams (degrees)
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