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holl_ands | Home > Omni & Quasi-Omni Directional Antennas > Browse:FM Flat-Swept SBGH H-POL OMNI-PLUSFM TRIAD 4xRectangular-Loops H-OMNI-PLUSFM Goalkeeper Quad-Trap+Spurs Quasi-OMNIFM TRIAD Array of Dipoles H-OMNIFM Double-Hoop H-POL OMNIFM Double-Hoop + Vertical-Dipole OutsideFM Double-Hoop + Vertical-FD-OutsideFM Double-Hoop + Vert. Dipole In CenterFM Double-Hoop + Vertical-FD-In-CenterFM Double-Hoop + Vertical Whip OutsideFM Vertical Folded Dipole VPOL TRUE-OMNIFM Vertical Stick Dipole V-POL TRUE-OMNIFM + VHF Discone V-POL TRUE-OMNIFM Monopole Whip over Groundplane OMNIFM Turnstile QuasiOMNI Antennacraft FMSSFM Turnstile Quasi-Omni - AlternateFM Turnstile - A-C FMSS RotatedFM ESS Curves - Fracarro & DipolFM ZigZag - Triax FM ZigmaFM Right Circular Folded Dipole PairFM Cycloid Dipole - Circular Polarized490 MHz Flat-Swept SBGH H-POL OMNI-PLUS490 MHz Flat-Swept SBGH OMNI + TOP-HAT490 MHz 3-Dipole TRIAD Array H-POL OMNI490 MHz Crossed-Dipoles + One TL - OMNI490 MHz Crossed-Dipoles, 2 Unequal TLs490 MHz 7-El Yagi TRIAD H-POL OMNI-PLUS490 MHz 4El Yagi Triad H-POL True-OMNI490 MHz Collinear Helical HPOL OMNI-PLUS490 MHz Double Diamond H-POL Quasi-OMNIUHF Vertical Folded Dipole V-POL OMNIUHF SBGH H-POL OMNI-PLUS by nikimlUHF Hoverman Type 1 H-POL Quasi-OmniUHF M4 (10x9.5) Twisted 4-Bay Quasi-OMNIUHF 2xM4 Twisted 8-Bay - Quasi-OMNIHi-VHF Goalkeeper Quad-Trapezoid+SpursHi-VHF Monopole Whip V-POL TRUE-OMNIHi-VHF Vertical Folded Dipole OMNICh2-69 Crossed Loops 90-deg Phase ShiftCh2-69 + FM Crossed Loops - UVOX-22m "Classic" 3QWL+QWL J-Pole
490 MHz Crossed-Dipoles + One TL - OMNI 490 MHz Crossed Dipoles (Interconnected with One Feedline), analyzed using 4nec2 after Dimensions determined using nikiml's Python Optimization Scripts. Azimuthal Pattern for Horizontal Polarization is a TRUE OMNI with about -1 dBi Gain (+/- 1 dB) and very low SWR (Under 1.03).  Horizontal Gain was only slightly reduced for moderate to large negative Elevation Angles, hence Look Down Angle coverage is Very Good. Azimuthal Pattern for Right Hand Circular Polarization (RHCP) was not quite a True Omni with about -3 dbc Gain (+/- 1.5 dB) and very low SWR (Under 1.03).  Note that as shown, RHCP covers LOWER Hemisphere.  To change so RHCP covers UPPER Hemisphere, reverse Feedlines to Upper Dipole. For about 3 dB more Gain, two Vertically Stacked Crossed Dipoles could be used. And for about ANOTHER 3 dB more Gain a Turnstile with FOUR Crossed Dipoles could be used. SUMMARY OF DIMENSIONS: [From 4nec2 File] Relem=5               ' Element Radius (millimeters) VF1=1.00              ' Feedline Velocity Factor [OPEN LADDER] F=0.996                 ' RESCALE FACTOR [487 TO 490 MHZ] HL=F*125=124.5   ' Half-Length of Dipoles (millimeters) (Max Y-axis Coordinates) Zdd=20                 ' Z-Axis Dipole-to-Dipoles Separation L1=F*28.5=28.4    ' Feedine PHYSICAL Length (IN MM) Between Dipoles FL1=VF1*L1/1000=0.0284  ' Feedline Electrical Length (IN METERS) between Dipoles Zc1=342                ' Characteristic Impedance (ohms) of Feedline Between Dipoles Resultant Optimization favored the lowest SWR, rather than Uniform Gain in all directions. Hence I applied a small RESCALE FACTOR to recenter "Best" performance from 487 to 490 MHz. Due to short length (28.4-mm), construction of the Interconnecting Feedline is NOT critical, with 0.75-in separation between AWG10 or AWG12 or AWG14 working equally well. Date(s): 3 May 2016. Album by holl_ands. 1 - 39 of 39 Total. 2072 Visits.
enlarge 54KB, 1024x840 1 490MHz Crossed-Dipoles + One TL 3D View enlarge 102KB, 1152x332 2 490MHz Crossed-Dipoles + One TL Front View [1 large square = 25-mm] enlarge 285KB, 1019x1024 3 490MHz Crossed-Dipoles + One TL Top View [1 large square = 25-mm] enlarge 182KB, 1152x703 4 490MHz Crossed-Dipoles + One TL UHF Raw Gain from 486 to 494 MHz enlarge 196KB, 1152x703 5 490MHz Crossed-Dipoles + One TL UHF SWR (50-ohms) from 486 to 494 MHz Under 1.03 enlarge 234KB, 1152x703 6 490MHz Crossed-Dipoles + One TL UHF Impedance from 486 to 494 MHz enlarge 215KB, 1152x703 7 490MHz Crossed-Dipoles + One TL UHF Raw Gain is Wideband enlarge 235KB, 1152x703 8 490MHz Crossed-Dipoles + One TL UHF SWR (50-ohms) is Wideband enlarge 255KB, 1152x703 9 490MHz Crossed-Dipoles + One TL UHF Impedance enlarge 300KB, 1024x1024 10 490MHz Crossed-Dipoles + One TL Azimuthal Pattern - Horizontal Pol. Raw Gain = -1.9 to -0.8 dBi At 486 MHz enlarge 299KB, 1024x1024 11 490MHz Crossed-Dipoles + One TL Azimuthal Pattern - Horizontal Pol. Raw Gain = -1.8 to -0.8 dBi At 490 MHz enlarge 299KB, 1024x1024 12 490MHz Crossed-Dipoles + One TL Azimuthal Pattern - Horizontal Pol. Raw Gain = -1.9 to -0.5 dBi At 494 MHz enlarge 308KB, 1024x1024 13 490MHz Crossed-Dipoles + One TL H-Pol. Azimuthal Pattern At Elev = -10-deg Raw Gain = -1.8 to -0.8 dBi At 490 MHz enlarge 315KB, 1024x1024 14 490MHz Crossed-Dipoles + One TL H-Pol. Azimuthal Pattern At Elev = -20-deg Raw Gain = -2.0 to -0.8 dBi At 490 MHz enlarge 324KB, 1024x1024 15 490MHz Crossed-Dipoles + One TL H-Pol. Azimuthal Pattern At Elev = -30-deg Raw Gain = -2.1 to -0.7 dBi At 490 MHz enlarge 329KB, 1024x1024 16 490MHz Crossed-Dipoles + One TL H-Pol. Azimuthal Pattern At Elev = -40-deg Raw Gain = -2.1 to -0.7 dBi At 490 MHz enlarge 335KB, 1024x1024 17 490MHz Crossed-Dipoles + One TL H-Pol. Azimuthal Pattern At Elev = -50-deg Raw Gain = -2.1 to -0.5 dBi At 490 MHz enlarge 333KB, 1024x1024 18 490MHz Crossed-Dipoles + One TL H-Pol. Azimuthal Pattern At Elev = -60-deg Raw Gain = -2.1 to -0.4 dBi At 490 MHz enlarge 325KB, 1024x1024 19 490MHz Crossed-Dipoles + One TL H-Pol. Elevation Pattern At Azim. = 90-deg Raw Gain = -0.8 to -0.8 dBi At 490 MHz enlarge 327KB, 1024x1024 20 490MHz Crossed-Dipoles + One TL H-Pol. Elevation Pattern At Azim. = 44-deg Raw Gain = -2.0 to -0.1 dBi At 490 MHz enlarge 320KB, 1024x1024 21 490MHz Crossed-Dipoles + One TL H-Pol. Elevation Pattern At Azim. = 0-deg Raw Gain = -1.1 to -1.1 dBi At 490 MHz enlarge 29KB, 791x1024 22 490MHz Crossed-Dipoles + One TL 4nec2 file includes Summary of Dimensions enlarge 91KB, 791x1024 23 490MHz Crossed-Dipoles + One TL EVAL *.html Performance summary enlarge 101KB, 1152x327 24 490MHz Crossed-Dipoles + One TL Side View [1 large square = 25-mm] enlarge 309KB, 1024x1024 25 490MHz Crossed-Dipoles + One TL RHCP Azimuthal Pattern, Elev= 0-deg Raw Gain = -4.8 to -3.8 dBc At 490 MHz enlarge 324KB, 1024x1024 26 490MHz Crossed-Dipoles + One TL RHCP Azimuthal Pattern, Elev= -10-deg Raw Gain = -3.5 to -2.7 dBc at 490 MHz enlarge 324KB, 1024x1024 27 490MHz Crossed-Dipoles + One TL RHCP Azimuthal Pattern, Elev= -20-deg Raw Gain = -2.3 to -1.6 dBc at 490 MHz enlarge 316KB, 1024x1024 28 490MHz Crossed-Dipoles + One TL RHCP Azimuthal Pattern, Elev= -30-deg Raw Gain = -1.2 to -0.7 dBc at 490 MHz enlarge 319KB, 1024x1024 29 490MHz Crossed-Dipoles + One TL RHCP Azimuthal Pattern, Elev= -40-deg Raw Gain = -0.3 to 0.1 dBc at 490 MHz enlarge 317KB, 1024x1024 30 490MHz Crossed-Dipoles + One TL RHCP Azimuthal Pattern, Elev= -50-deg Raw Gain = 0.5 to 0.7 dBc at 490 MHz enlarge 313KB, 1024x1024 31 490MHz Crossed-Dipoles + One TL RHCP Azimuthal Pattern, Elev= -60-deg Raw Gain = 1.2 to 1.3 dBc at 490 MHz enlarge 309KB, 1024x1024 32 490MHz Crossed-Dipoles + One TL RHCP Azimuthal Pattern, Elev= -70-deg Raw Gain = 1.6 to 1.7 dBc at 490 MHz enlarge 305KB, 1024x1024 33 490MHz Crossed-Dipoles + One TL RHCP Azimuthal Pattern, Elev= -80-deg Raw Gain = 1.9 to 1.9 dBc at 490 MHz enlarge 316KB, 1024x1024 34 490MHz Crossed-Dipoles + One TL RHCP Elevation Pattern, Azim=50-deg Raw Gain = -27.0 to 2.0 dBc at 490 MHz enlarge 317KB, 1024x1024 35 490MHz Crossed-Dipoles + One TL RHCP Elevation Pattern, Azim=40-deg Raw Gain = -65.0 to 2.0 dBc at 490 MHz enlarge 316KB, 1024x1024 36 490MHz Crossed-Dipoles + One TL RHCP Elevation Pattern, Azim=0-deg Raw Gain = -19.0 to 2.0 dBc at 490 MHz enlarge 318KB, 1024x1024 37 490MHz Crossed-Dipoles + One TL RHCP Elevation Pattern, Azim=220-deg Raw Gain = -65.0 to 2.0 dBc at 490 MHz enlarge 316KB, 1024x1024 38 490MHz Crossed-Dipoles + One TL RHCP Elevation Pattern, Azim=180-deg Raw Gain = -19.0 to 2.0 dBc at 490 MHz enlarge 317KB, 1024x1024 39 490MHz Crossed-Dipoles + One TL RHCP Elevation Pattern, Azim=140-deg Raw Gain = -18.0 to 2.0 dBc at 490 MHz
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