• Public Gallery  • Help
		• Join Now!  • Log In  • Feature Tour

holl_ands | Home > Circular Polarized incl. Rabbit-Ears > Helical Circular Polarized > Browse:Hi-VHF Helical - Offset FeedHi-VHF Helical - Center Feed
Hi-VHF Helical - Center Feed Hi-VHF Helical (Axial-Mode) Antennas with Center Feed is analyzed using 4nec2. 1) Hi-VHF: Center Feed, 185 MHz Design Frequency, 5.5 Turns, C/WL=1.133 (presumably close to optimum), Alpha=arctan(S/C)=14.5-deg (presumably close to optimum), where C=Helix Circumference, WL=Wavelength, Alpha=Helix Spiral Angle and S=Size of One Turn along the X-axis. Calculated parameters: R=29.24-cm (11.5")=Helix Radius, S=47.52-cm (18.7") and L=2.6134-m (102.9")=Helix Length. Characteristic Impedance is optimum (under 1.24) for 120-ohms, but is still quite good at 75-ohms, as plotted below. EDIT (16 Jan 2011): Added Circular Polarization Patterns as an Animated-GIF. Only Good for the lowest frequencies.  NEEDS FURTHER INVESTIGATION AND/OR REDESIGN!!!! Date(s): 9 Feb 2001. Album by holl_ands. 1 - 19 of 19 Total. 1628 Visits.
enlarge 128KB, 1024x875 1 Hi-VHF 5.5-Turn Helical, C/WL=1.133, Alpha=14.5-deg Design Frequency = 185 MHz for Best Gain, F/B & SWR Center Feedpoint: 3D View enlarge 164KB, 1152x494 2 Hi-VHF 5.5-Turn Helical, C/WL=1.133, Alpha=14.5-deg Center Feedpoint: Side View [1 small box = 2.5 cm] enlarge 304KB, 1024x881 3 Hi-VHF 5.5-Turn Helical, C/WL=1.133, Alpha=14.5-deg Center Feedpoint: Front View [1 small box = 5 cm] enlarge 171KB, 895x1024 4 Hi-VHF 5.5-Turn Helical, C/WL=1.133, Alpha=14.5-deg Center Feedpoint: 3D View DETAIL enlarge 163KB, 1152x487 5 Hi-VHF 5.5-Turn Helical, C/WL=1.133, Alpha=14.5-deg Center Feedpoint: Top View [1 small box = 2.5 cm] enlarge 41KB, 791x1024 6 Hi-VHF 5.5-Turn Helical, C/WL=1.133, Alpha=14.5-deg Center Feedpoint: 4nec2 File enlarge 166KB, 1152x717 7 Hi-VHF 5.5-Turn Helical, C/WL=1.133, Alpha=14.5-deg Center Feedpoint: Raw Gain Ch7-13 enlarge 197KB, 1152x717 8 Hi-VHF 5.5-Turn Helical, C/WL=1.133, Alpha=14.5-deg Center Feedpoint: SWR (75-ohms) Ch7-13 enlarge 163KB, 1152x717 9 Hi-VHF 5.5-Turn Helical, C/WL=1.133, Alpha=14.5-deg Center Feedpoint: Impedance Ch7-13 enlarge 317KB, 1024x1024 10 Hi-VHF 5.5-Turn Helical, C/WL=1.133, Alpha=14.5-deg Center Feedpoint: Patterns at 174 MHz enlarge 322KB, 1024x1024 11 Hi-VHF 5.5-Turn Helical, C/WL=1.133, Alpha=14.5-deg Center Feedpoint: Patterns at 198 MHz enlarge 323KB, 1024x1024 12 Hi-VHF 5.5-Turn Helical, C/WL=1.133, Alpha=14.5-deg Center Feedpoint: Patterns at 216 MHz enlarge 158KB, 1024x786 13 Hi-VHF 5.5-Turn Helical, C/WL=1.133, Alpha=14.5-deg Center Feedpoint: 3D Total Pattern at 198 MHz enlarge 144KB, 1024x789 14 Hi-VHF 5.5-Turn Helical, C/WL=1.133, Alpha=14.5-deg Center Feedpoint: 3D Horiz Pattern at 198 MHz enlarge 151KB, 1024x792 15 Hi-VHF 5.5-Turn Helical, C/WL=1.133, Alpha=14.5-deg Center Feedpoint: 3D Vertical Pattern at 198 MHz enlarge 193KB, 1152x717 16 Hi-VHF 5.5-Turn Helical, C/WL=1.133, Alpha=14.5-deg Center Feedpoint: Raw Gain FM to 300MHz enlarge 215KB, 1152x717 17 Hi-VHF 5.5-Turn Helical, C/WL=1.133, Alpha=14.5-deg Center Feedpoint: SWR (75-ohms) FM to 300MHz enlarge 173KB, 1152x717 18 Hi-VHF 5.5-Turn Helical, C/WL=1.133, Alpha=14.5-deg Center Feedpoint: Impedance FM to 300MHz enlarge 352KB, 1024x1024 19 Hi-VHF 5.5-Turn Helical, C/WL=1.133, Alpha=14.5-deg Center Feedpoint - Ani-Gif Circular Polarization Patterns Only Good for the lowest frequencies. NEEDS FURTHER INVESTIGATION AND/OR REDESIGN!!!!
Select All.
Sign the Guestbook. There are no entries.