490-MHz 3-Dipole Triangle Array, Horizontally-Polarized OMNI-Directional Antenna analyzed using 4nec2. This is one of the very few H-Pol. Antennas that are provide a TRUE OMNI Azimuthal Pattern, with an Outstanding Gain variability of only +/- 0.1 dB vs Angle and even less than that vs Frequency.
Gmin = 1.2 dBi, Gmax = 1.4 dBi. Characteristic Impedance = 200-ohms. Provides better Gain and SWR with 200-ohm Balun (requiring use of a 4:1 Balun (usually Coax type) than 50-ohm (with 1:1 Coax Balun)....whose SWR of about 1.7:1 was acceptable, but uncomfortably close to a typical Transmitter Limit of 2:1, leaving little room for other SWR detriments.
Although specifically designed for an 8-MHz bandwidth DVB-T Ch23 Very Low Power Transmitter, the dimensions can be Rescaled to any desired Center Frequency by Fraction F = New Freq / 490 MHz [Smaller for Higher Freqs].
Although NOT a problem with THIS OMNI Antenna, adequate signal levels very close to the Transmit Tower is of interest, since higher Gain Antennas may have an Elevation Gain Pattern that is TOO narrow with only minimal signal level being directed DOWN to nearby homes....bearing in mind that signal levels are 20 dB HIGHER at 0.1 km as they are at 1 km, as the Path Loss decreases ever closer to the Tower.
15 Feb 201615 items3273 visitsAlbum by holl_ands
enlarge 59KB, 1024x704 1 490 MHz 3-Dipole Triangle H-Polar. OMNI 3D View
enlarge 279KB, 1010x1024 2 490 MHz 3-Dipole Triangle H-Polar. OMNI Top View [1 large square = 1.25-inches]
enlarge 117KB, 1152x408 3 490 MHz 3-Dipole Triangle H-Polar. OMNI Front View [1 large square = 1.25-inches]
enlarge 209KB, 1152x703 4 490 MHz 3-Dipole Triangle H-Polar. OMNI Raw Gain = 1.5 dBi
enlarge 206KB, 1152x703 5 490 MHz 3-Dipole Triangle H-Polar. OMNI SWR (200-ohms) Under 1.2
enlarge 234KB, 1152x703 6 490 MHz 3-Dipole Triangle H-Polar. OMNI Impedance across the Band
enlarge 331KB, 1024x1024 7 490 MHz 3-Dipole Triangle H-Polar. OMNI Azimuthal Gain at 486 MHz = 1.3 to 1.5 dBi indicates it is a TRUE OMNI
enlarge 327KB, 1024x1024 8 490 MHz 3-Dipole Triangle H-Polar. OMNI Azimuthal Gain at 490 MHz = 1.3 to 1.5 dBi indicates it is a TRUE OMNI
enlarge 327KB, 1024x1024 9 490 MHz 3-Dipole Triangle H-Polar. OMNI Azimuthal Gain at 494 MHz = 1.3 to 1.5 dBi indicates it is a TRUE OMNI
enlarge 334KB, 1024x1024 10 490 MHz 3-Dipole Triangle H-Polar. OMNI Elevation Gain at 490 MHz -0.5 dB at 24-deg Look Down Angle -1.0 dB at 33-deg Look Down Angle -2.0 dB at 42-deg Look Down Angle -3.0 dB at 51-deg Look Down Angle -6.0 dB at 65-deg Look Down Angle
enlarge 246KB, 1024x744 11 490 MHz 3-Dipole Triangle H-Polar. OMNI Antenna Look Down Angle versus Tower Height Advantage (meters) [Difference between Tower and RX Antennas]
Viewers close to Tower have additional Look Down Loss, but are likely to also receive Reflections from surrounding houses.
enlarge 28KB, 791x1024 12 490 MHz 3-Dipole Triangle H-Polar. OMNI 4nec2 File includes Dimensions:
