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holl_ands | Home > Circular Polarized incl. Rabbit-Ears > Offset Crossed Dipoles > Browse:Hi-VHF Offset-Crossed FD's - TL=HWLHi-VHF Offset-Crossed FD's - 2TL=HWLHi-VHF Offset-Crossed FD's - 2TL=QWLHi-VHF Offset-Crossed FD's - TL=QWLHi-VHF Offset-Crossed FD's - 2TL=3QWL
Hi-VHF Offset-Crossed FD's - TL=HWL Hi-VHF Offset-Crossed Folded Dipoles (FD's) with Quarter-Wavelength offset between the FD's and HALF-Wavelength Transmission Line (simulated by TL Card) interconnecting the two FD's. This results in requisite 90-deg difference in signals arriving from each Folded Dipole for RHCP (Right Hand Circular Polarization). Optimum TL is 600-ohm Impedance, although 450-ohm may also be used with minor degradation to Gain and SWR.  [In diagrams below, Feedline is NOT TO SCALE.] With Quarter-Inch Copper Tubing (QICT), 2-in FD "Width" (distance between FD Elements) and Quarter-Wavelength Separation between the Crossed FD's, a large Gain and SWR GLITCH was found in the middle of the Hi-VHF Band, the placement depending on the overall FD Length: 189 MHz if 30-in, 202 MHz if 28-in, 210 MHz if 27-in, etc. If the length of the Cross-FDs are much longer or shorter than when used alone, the GLITCHES can be moved out-of-band.  FD Length = 23-in or 34-in was barely sufficient to avoid the GLITCHES, as shown below.  The longer 34-in FD was better with good RHCP Gain, very good LHCP suppression characteristics and good SWR. Note that Right Hand Circular Polarization is strong both FORWARD and REVERSE, but Left Hand suppression is stronger FORWARD.  Reversing one interconnection reverses Polarization, so VERY CAREFULLY check antenna connections and alignment.  Note 20+ dB of LHCP Suppression. Date(s): 21 Jan 2012. Album by holl_ands. 1 - 21 of 21 Total. 1247 Visits.
enlarge 46KB, 1024x978 1 Hi-VHF Offset-Cross FD's - TL=HWL Length = 34-in, FD Width = 2-in 3D View enlarge 297KB, 1024x967 2 Hi-VHF Offset-Cross FD's - TL=HWL Length = 34-in, FD Width = 2-in Front View [1 big box = 2.5-inches] enlarge 161KB, 540x1024 3 Hi-VHF Offset-Cross FD's - TL=HWL Length = 34-in, FD Width = 2-in Top View [1 big box = 2.5-inches] enlarge 162KB, 1024x686 4 Hi-VHF Offset-Cross FD's - TL=HWL Length = 34-in, FD Width = 2-in Hi-VHF Raw Gain ~ 2.2 to 2.5 dBi enlarge 181KB, 1024x686 5 Hi-VHF Offset-Cross FD's - TL=HWL Length = 34-in, FD Width = 2-in Hi-VHF SWR (300-ohms ) Under 2.7 enlarge 153KB, 1024x686 6 Hi-VHF Offset-Cross FD's - TL=HWL Length = 34-in, FD Width = 2-in Hi-VHF Impedance enlarge 335KB, 1024x1024 7 Hi-VHF Offset-Cross FD's - TL=HWL Length = 34-in, FD Width = 2-in Azimuthal Patterns at 174 MHz enlarge 332KB, 1024x1024 8 Hi-VHF Offset-Cross FD's - TL=HWL Length = 34-in, FD Width = 2-in Azimuthal Patterns at 186 MHz enlarge 332KB, 1024x1024 9 Hi-VHF Offset-Cross FD's - TL=HWL Length = 34-in, FD Width = 2-in Azimuthal Patterns at 198 MHz enlarge 334KB, 1024x1024 10 Hi-VHF Offset-Cross FD's - TL=HWL Length = 34-in, FD Width = 2-in Azimuthal Patterns at 210 MHz enlarge 338KB, 1024x1024 11 Hi-VHF Offset-Cross FD's - TL=HWL Length = 34-in, FD Width = 2-in Azimuthal Patterns at 216 MHz enlarge 161KB, 539x1024 12 Hi-VHF Offset-Cross FD's - TL=HWL Length = 34-in, FD Width = 2-in Side View [1 big box = 2.5-inches] enlarge 341KB, 1024x1024 13 Hi-VHF Offset-Cross FD's - TL=HWL Length = 34-in, FD Width = 2-in Circular Polarization Patterns at 174 MHz enlarge 339KB, 1024x1024 14 Hi-VHF Offset-Cross FD's - TL=HWL Length = 34-in, FD Width = 2-in Circular Polarization Patterns at 180 MHz enlarge 338KB, 1024x1024 15 Hi-VHF Offset-Cross FD's - TL=HWL Length = 34-in, FD Width = 2-in Circular Polarization Patterns at 186 MHz enlarge 338KB, 1024x1024 16 Hi-VHF Offset-Cross FD's - TL=HWL Length = 34-in, FD Width = 2-in Circular Polarization Patterns at 192 MHz enlarge 340KB, 1024x1024 17 Hi-VHF Offset-Cross FD's - TL=HWL Length = 34-in, FD Width = 2-in Circular Polarization Patterns at 198 MHz enlarge 340KB, 1024x1024 18 Hi-VHF Offset-Cross FD's - TL=HWL Length = 34-in, FD Width = 2-in Circular Polarization Patterns at 210 MHz enlarge 343KB, 1024x1024 19 Hi-VHF Offset-Cross FD's - TL=HWL Length = 34-in, FD Width = 2-in Circular Polarization Patterns at 216 MHz enlarge 338KB, 1024x1024 20 Hi-VHF Offset-Cross FD's - TL=HWL Length = 34-in, FD Width = 2-in Circular Polarization Patterns - Ani-Gif enlarge 30KB, 791x1024 21 Hi-VHF Offset-Cross FD's - TL=HWL Length = 34-in, FD Width = 2-in 4nec2 File
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