490-MHz Flat-Swept SBGH (Single-Bay Grey-Hoverman), Horizontally-Polarized OMNI-Directional Antenna with 36-in Radius "Top-Hat" [to improve Look-Down Angle, i.e. Negative Elevation Pattern Gain] was analyzed using 4nec2.
Min Gain = 7.1 dBi, Max Gain = 9.0 dBi. Although this H-Pol. Antenna doesn't provide TRUE OMNI Azimuthal Pattern (equal Gain every direction), it DOES provide a MINIMUM Gain of 7.1 dBi or MORE on ALL Azimuths. It is well matched to a Characteristic Impedance of 200-ohms, requiring the use of a 4:1 Balun (usually Coax type) to match 50-ohm Load with an SWR of less than 1.5:1, which is well within a typical Transmitter Limit of 2:1.
Although specifically designed for an 8-MHz bandwidth DVB-T Ch23 Micro-Transmitter, the dimensions can be Rescaled to any desired Center Frequency by Fraction F = New Freq / 490 MHz [Smaller for Higher Freqs].
27 Feb 201614 items3266 visitsAlbum by holl_ands
enlarge 90KB, 1020x1024 1 490 MHz Flat-Swept SBGH OMNI + TOP-HAT 3D View
enlarge 216KB, 904x1024 2 490 MHz Flat-Swept SBGH OMNI + TOP-HAT Front View [1 Large Square = 12.5-inches]
36-in Radius Top-Hat is 45-in Above Origin (Center of Antenna)
enlarge 438KB, 1011x1024 3 490 MHz Flat-Swept SBGH OMNI + TOP-HAT Top View [1 Large Square = 12.5-inches]
enlarge 107KB, 1152x415 4 490 MHz Flat-Swept SBGH OMNI + TOP-HAT Raw Gain = 9.0 to 9.2 dBi
enlarge 223KB, 1152x703 5 490 MHz Flat-Swept SBGH OMNI + TOP-HAT UHF SWR Min = 1.4 at 490 MHz
enlarge 235KB, 1152x703 6 490 MHz Flat-Swept SBGH OMNI + TOP-HAT UHF Impedance = 240 to 250-ohms near 490 MHz
enlarge 308KB, 1024x1024 7 490 MHz Flat-Swept SBGH OMNI + TOP-HAT Azimuthal Pattern = 7.1 to 9.0 at 490 MHz
enlarge 300KB, 1024x1024 8 490 MHz Flat-Swept SBGH OMNI + TOP-HAT Elevation Pattern at 490 MHz Moderate increase in Look Down Angle Gain But Deep Nulls are still Present
enlarge 211KB, 904x1024 9 490 MHz Flat-Swept SBGH OMNI + TOP-HAT Side View [1 Large Square = 12.5-inches]
enlarge 250KB, 791x1024 10 490 MHz Flat-Swept SBGH OMNI + TOP-HAT 4nec2 File includes Summary of Dimensions
enlarge 26KB, 791x1024 11 490 MHz Flat-Swept SBGH OMNI + TOP-HAT EVAL Summary of Performance Text File
