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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, 2 Unequal TLs 490 MHz Vertically Stacked Crossed Dipoles (Interconnected with two Unequal Feedlines), analyzed using 4nec2 after Dimensions determined using nikiml's Python Optimization Scripts. It was found to be a TRUE OMNI, with roughly SAME Gain on all Azimuths, but SWR was poor and would need an additional Matching Network or Quarter-Wavelength Impedance Transformer. Horizontally Polarized Raw Gain = -1.5 dBi (+/- 1 dB) and SWR (50-ohms) = 2.0, which is right at limit for tripping the self-protect circuitry in some Transmitters, with no margin left to accommodate likely SWR degradations in the Feedline, construction inaccuracies and Proximity to Nearby Objects. SUMMARY OF DIMENSIONS: [From 4nec2 File] Relem=5          ' Element Radius Gap=20           ' FEEDPOINT GAP (SIMULATED BALUN CONNECTION) VF1=0.66          ' Velocity Factor, Feedline to Top Dipole VF2=0.66          ' Velocity Factor, Feedline to Top Dipole ' Half-Length of Dipoles (millimeters) (Max Y-axis Coordinates): HL=152 ' Distance Dipoles are Above and Below Z=0 Axis (millimeters): Zd1=150 Zd2=250 ' Feedine PHYSICAL Length (IN METERS) to Top & Bottom Dipoles: L1=0.244 L2=0.400 ' Feedline Electrical Length (IN METERS) to Top & Bottom Dipoles: FL1=VF1*L1 FL2=VF2*L2 ' Characteristic Impedance of Feedlines to Top & Bottom Dipoles: Zc1=85     [75-ohm Coax is close enough] Zc2=205    [Non-Standard Value] Date(s): 3 May 2016. Album by holl_ands. 1 - 24 of 24 Total. 1841 Visits.
enlarge 47KB, 691x1024 1 490MHz Crossed-Dipoles, 2 Unequal TLs 3D View enlarge 219KB, 840x1024 2 490MHz Crossed-Dipoles, 2 Unequal TLs Front View [1 large square = 50-mm] enlarge 310KB, 1013x1024 3 490MHz Crossed-Dipoles, 2 Unequal TLs Top View [1 large square = 25-mm] enlarge 184KB, 1152x703 4 490MHz Crossed-Dipoles, 2 Unequal TLs Raw Gain from 486 to 494 MHz enlarge 209KB, 1152x703 5 490MHz Crossed-Dipoles, 2 Unequal TLs SWR (50-ohms) = 2.0 from 486 to 494 MHz enlarge 217KB, 1152x703 6 490MHz Crossed-Dipoles, 2 Unequal TLs Impedance from 486 to 494 MHz enlarge 197KB, 1152x703 7 490MHz Crossed-Dipoles, 2 Unequal TLs Wideband Raw Gain enlarge 208KB, 1152x703 8 490MHz Crossed-Dipoles, 2 Unequal TLs Wideband SWR (50-ohms) enlarge 239KB, 1152x703 9 490MHz Crossed-Dipoles, 2 Unequal TLs Wideband Impedance enlarge 300KB, 1024x1024 10 490MHz Crossed-Dipoles, 2 Unequal TLs Azimuthal Pattern At 486 MHz Horiz. Raw Gain = -2.3 to -0.6 dBi enlarge 299KB, 1024x1024 11 490MHz Crossed-Dipoles, 2 Unequal TLs Azimuthal Pattern At 490 MHz Horiz. Raw Gain = -2.0 to -0.7 dBi enlarge 300KB, 1024x1024 12 490MHz Crossed-Dipoles, 2 Unequal TLs Azimuthal Pattern At 494 MHz Horiz. Raw Gain = -2.2 to -0.6 dBi enlarge 320KB, 1024x1024 13 490MHz Crossed-Dipoles, 2 Unequal TLs Azimuthal Pattern At 350 MHz enlarge 321KB, 1024x1024 14 490MHz Crossed-Dipoles, 2 Unequal TLs Azimuthal Pattern At 400 MHz enlarge 321KB, 1024x1024 15 490MHz Crossed-Dipoles, 2 Unequal TLs Azimuthal Pattern At 450 MHz enlarge 317KB, 1024x1024 16 490MHz Crossed-Dipoles, 2 Unequal TLs Azimuthal Pattern At 550 MHz enlarge 321KB, 1024x1024 17 490MHz Crossed-Dipoles, 2 Unequal TLs Azimuthal Pattern At 600 MHz enlarge 320KB, 1024x1024 18 490MHz Crossed-Dipoles, 2 Unequal TLs Azimuthal Pattern At 650 MHz enlarge 321KB, 1024x1024 19 490MHz Crossed-Dipoles, 2 Unequal TLs Elevation Pattern At 486 MHz Horiz. Raw Gain = -1.3 to -0.1 dBi enlarge 320KB, 1024x1024 20 490MHz Crossed-Dipoles, 2 Unequal TLs Elevation Pattern At 490 MHz Horiz. Raw Gain = -1.5 to -0.3 dBi enlarge 320KB, 1024x1024 21 490MHz Crossed-Dipoles, 2 Unequal TLs Elevation Pattern At 494 MHz Horiz. Raw Gain = -1.8 to -0.5 dBi enlarge 29KB, 791x1024 22 490MHz Crossed-Dipoles, 2 Unequal TLs 4nec2 File includes Summary of Dimensions enlarge 91KB, 791x1024 23 490MHz Crossed-Dipoles, 2 Unequal TLs EVAL *.html Performance Summary enlarge 225KB, 835x1024 24 490MHz Crossed-Dipoles, 2 Unequal TLs Side View [1 large square = 50-mm]
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