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FM Turnstile - Antennacraft FMSS
Antennacraft FMSS FM Turnstile (two Folded Dipoles at 90-degrees to each other) analyzed using 4nec2.
[Similar to Wade CFM-FM, Wade OFM-1 and Winegard HD-6010, except non-Folded is 75-ohm output.]

Per FMSS Specs, Folded Dipole Elements = 55-in long with overall structure Height = 8-in.
Separation between Elements appears to be about 2-in, leaving about 4-in between the Crossed FD's.
Per FMSS Manual, Feedline is 9-in long and appears to be 450-ohms open ladder twinlead,
although modeling with 300-ohm twinlead revealed minimal differences, assuming it was the
same ELECTRICAL length (shorten by velocity factor).

Antenna Pattern maximums are 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 -14 to +1.3 dB (Horizontally Polarized).
SWR (300-ohms) was 2.9, dropping to 1.5 at high frequencies.

FYI: FMSS Folded Dipole lengths are not quite optimum for Min SWR.  Longer, 62.5-in FD Elements
minimized SWR, which was under 1.9, but decreased Raw Gain by a few tenths of a dB.
Date(s): 22 Dec 2011. Album by holl_ands. 1 - 17 of 17 Total. 6329 Visits.
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FM Turnstile - Antennacraft FMSS
3D View

Study this diagram very carefully to determine
diagonal direction for Max Gain.


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FM Turnstile - Antennacraft FMSS
"Front" View
[1 big box = 5-inches]


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FM Turnstile - Antennacraft FMSS
Top View
[1 big box = 5-inches]


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FM Turnstile - Antennacraft FMSS
FM Raw Gain FORWARD (90-deg)
Gain Loss on Low Frequencies


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FM Turnstile - Antennacraft FMSS
FM Raw Gain on DIAGONAL (45-deg)
Large Gain Loss on ALL Frequencies


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FM Turnstile - Antennacraft FMSS
FM Raw Gain to SIDE (0-deg)
Gain Loss on High Frequencies


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FM Turnstile - Antennacraft FMSS
FM Raw Gain on DIAGONAL (300-deg)
Gain Loss on Low Frequencies


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FM Turnstile - Antennacraft FMSS
FM Raw Gain on DIAGONAL (335-deg)
Gain Loss on High Frequencies


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FM Turnstile - Antennacraft FMSS
FM SWR (300-ohms) Under 2.9


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FM Turnstile - Antennacraft FMSS
FM Impedance


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FM Turnstile - Antennacraft FMSS
4nec2 File


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FM Turnstile - Antennacraft FMSS
"Side" View
[1 big box = 5-inches]


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FM Turnstile - Antennacraft FMSS
Azimuthal Pattern at 87 MHz


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FM Turnstile - Antennacraft FMSS
Azimuthal Pattern at 91 MHz


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FM Turnstile - Antennacraft FMSS
Azimuthal Pattern at 97 MHz


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FM Turnstile - Antennacraft FMSS
Azimuthal Pattern at 103 MHz


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FM Turnstile - Antennacraft FMSS
Azimuthal Pattern at 108 MHz


 
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I'm not even a hobbyist of antennas. Just want really good reception. I found this site trying to figure out if the AntennaCraft FMSS omni can be mistakenly placed upside down, or should it be, or should it be placed vertically so the x axis is pointing toward the stations I like (college,PBS, 88 - 92Mhz). I know it's advertised as omni-dir. Does that mean spherically? or 360* on the horizontal plane? The diagrams are all based on the antenna in the horizontal position (z axis vertical). So I set mine that way and it does work fairly well, but not excellent. Can anyone help point me in the right direction? :) please!
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edward, Sun, 25 Aug 2013 10:22AM