FM Turnstile (two Folded Dipoles at 90-degrees to each other) analyzed using 4nec2. Separation between Folded Dipole Elements = 3-in, overall Height = 14-in.
Folded Dipole lengths were tweaked to minimize SWR, resulting in two different lengths: 51.5-in for 75-ohms and 62-in for 300-ohms, presuming 3-in FD Element Separation. Both are shown below.
Antenna Pattern maximum is on two diagonals, 300-deg for High Freqs and 335-deg for Low Freqs. There are significant Gain Holes on the opposite Diagonals (40-60 & 220-240 degrees).
Across all angles and frequencies, Raw Gain ranges from -13 to +1.4 dB (Horizontally Polarized). SWR (75-ohms) is 1.8-3.2 with minimum mid-band, however SWR (300-ohms) is 3.5 dropping to 1.6, so either may be used.
21 Dec 201117 items5317 visitsAlbum by holl_ands
enlarge 71KB, 1024x778 1 FM Turnstile 51.5-in Quasi-Omni 3D View
Study this diagram very carefully to determine diagonal direction for Max Gain.
enlarge 111KB, 1152x367 2 FM Turnstile 51.5-in Quasi-Omni "Front" View [1 big box = 5-inches]
enlarge 252KB, 1024x969 3 FM Turnstile 51.5-in Quasi-Omni Top View [1 big box = 5-inches]
enlarge 148KB, 1152x584 4 FM Turnstile 51.5-in Quasi-Omni FM Raw Gain FORWARD (Horiz. Pol.)
enlarge 136KB, 1152x584 5 FM Turnstile 51.5-in Quasi-Omni FM Raw Gain to "SIDE" (0-deg)
enlarge 138KB, 1152x584 6 FM Turnstile 51.5-in Quasi-Omni FM Raw Gain on 300-deg Diagonal Max on High Freqs
enlarge 154KB, 1152x584 7 FM Turnstile 51.5-in Quasi-Omni FM Raw Gain on 300-deg Diagonal Max on Low Freqs
enlarge 167KB, 1152x584 8 FM Turnstile 51.5-in Quasi-Omni FM SWR (75-ohms) is 1.8-3.2
enlarge 167KB, 1152x584 9 FM Turnstile Quasi-Omni FM SWR (300-ohms) is 3.5-1.6
enlarge 155KB, 1152x584 10 FM Turnstile Quasi-Omni FM Impedance
enlarge 118KB, 1152x385 11 FM Turnstile Quasi-Omni "Side" View [1 big box = 5-inches]
enlarge 26KB, 791x1024 12 FM Turnstile Quasi-Omni 4nec2 File
enlarge 327KB, 1024x1024 13 FM Turnstile Quasi-Omni Azimuthal Pattern at 87 MHz
enlarge 326KB, 1024x1024 14 FM Turnstile Quasi-Omni Azimuthal Pattern at 91 MHz
enlarge 321KB, 1024x1024 15 FM Turnstile Quasi-Omni Azimuthal Pattern at 97 MHz
enlarge 320KB, 1024x1024 16 FM Turnstile Quasi-Omni Azimuthal Pattern at 103 MHz
enlarge 320KB, 1024x1024 17 FM Turnstile Quasi-Omni Azimuthal Pattern at 108 MHz
