490 MHz Horizontally Polarized Double Diamond Quad Quasi-OMNI-Directional Antenna analyzed using 4nec2 after Optimizing for 200-ohm Load using nikiml's Python Optimization Scripts. This was the "Best" of 9 Runs, including different assumed Load Impedance. Unfortunately, High Gain was NOT maintained across entire 8 MHz Channel Bandwidth.
Raw Gain was 4.6 to 5.4 dBi on 490 MHz, but degraded to an OBLATE shape, with 1.9 to 7.0 dBi on 486 MHz and 2.4 to 6.7 dBi on 494 MHz. SWR Max was an Excellent 1.4 across the 486-494 MHz Operating Band. DEEP NULL near 32-deg Look-Down Angle can result in an Annulus Ring of Problematic Reception.
enlarge 182KB, 521x1024 2 490MHz H-POL Double Diamond Quasi-OMNI Front View [1 large square = 2.5-inches] Physical Location of SIMULATED Transmission Lines (TL) is Immaterial and NOT TO SCALE.
enlarge 166KB, 528x1024 3 490MHz H-POL Double Diamond Quasi-OMNI Top View [1 large square = 1.25-inches] Physical Location of SIMULATED Transmission Lines (TL) is Immaterial and NOT TO SCALE.
enlarge 78KB, 855x1024 4 490MHz H-POL Double Diamond Quasi-OMNI 3D DETAIL at Feedpoint Transmission Line Feeds each Quad. About 1/4-wavelength difference between TL's provides approximate 90-deg Phase Shift
enlarge 128KB, 353x1024 5 490MHz H-POL Double Diamond Quasi-OMNI Side View [1 large square = 2.5-inches]
enlarge 30KB, 791x1024 6 490MHz H-POL Double Diamond Quasi-OMNI 4nec2 File includes Summary of Dimensions [View with FREE 4nec2 S/W or nikiml's on-line Viewer.]
enlarge 202KB, 1152x703 7 490MHz H-POL Double Diamond Quasi-OMNI UHF Raw Gain is MINIMUM Near Operating Band
enlarge 209KB, 1152x703 8 490MHz H-POL Double Diamond Quasi-OMNI UHF SWR (200-ohms) is MINIMUM Near Operating Band
enlarge 291KB, 958x1024 10 490MHz H-POL Double Diamond Quasi-OMNI Raw Gain = 1.9 to 7.0 dBi for 486 MHz No better than Dipole for large swath of Azimuths
enlarge 277KB, 944x1024 11 490MHz H-POL Double Diamond Quasi-OMNI Raw Gain = 4.6 to 5.4 dBi for 490 MHz Excellent OMNI-PLUS Azimuthal Response, but Bandwidth is WAY TOO NARROW.
enlarge 291KB, 956x1024 12 490MHz H-POL Double Diamond Quasi-OMNI Raw Gain = 2.4 to 6.7 dBi for 494 MHz No better than Dipole for large swath of Azimuths
enlarge 327KB, 1024x1024 13 490MHz H-POL Double Diamond Quasi-OMNI Elevation Gain for [RED] Horiz. Polarized signals NULL at Look-Down Angles near 32-deg which can result in an Annulus of Problematic Reception
enlarge 314KB, 1024x1024 14 490MHz H-POL Double Diamond Quasi-OMNI Azimuthal Gain for 20-deg Look-Down Angle Gain about -1 dBi for Horiz. Polarized signals
enlarge 294KB, 1024x1024 15 490MHz H-POL Double Diamond Quasi-OMNI Azimuthal Gain for 32-deg Look-Down Angle EXCESSIVE LOSS for Horiz. Polarized signals
enlarge 302KB, 1024x1024 16 490MHz H-POL Double Diamond Quasi-OMNI Azimuthal Gain for 40-deg Look-Down Angle Gain about -9 dBi for Horiz. Polarized signals
enlarge 290KB, 1024x1024 17 490MHz H-POL Double Diamond Quasi-OMNI Azimuthal Gain for 50-deg Look-Down Angle Gain about -5 dBi for Horiz. Polarized signals
enlarge 299KB, 1024x1024 18 490MHz H-POL Double Diamond Quasi-OMNI Azimuthal Gain for 60-deg Look-Down Angle Gain about -5 dBi for Horiz. Polarized signals
