285:. The radiation off one end is righthand-circularly-polarized and the other end is lefthand-circularly-polarized. Which end produces which polarization is determined by the phase of the feed connections. Since in a directional antenna only a single beam is wanted, in a simple axial-mode antenna a flat conducting surface such as a metal screen reflector is added, a quarter-wavelength behind the crossed elements. The waves in that direction are reflected back 180° and the reflection reverses the polarization sense, so the reflected waves reinforce the forward radiation. For example, if the radio waves radiated forward are right-circularly-polarized, the waves radiated backwards will be left-circularly-polarized. The flat reflector reverses the polarization sense so the reflected waves are right-circularly-polarized. By locating the reflector λ/4 behind the elements the direct and reflected waves are in phase and add. Addition of the reflector increases the axial radiation by a factor of 2 (3 dB).
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increases the gain by strengthening the radiation in the desired horizontal directions but causes partial cancellation of the radiation in vertical directions, reducing power wasted radiated into the sky or down toward the earth. These stacked normal mode turnstile antennas are used at VHF and UHF frequencies for FM and television broadcasting.
332:
By modifying the length and shape of the dipoles, the combined terminal impedance presented to a single feed-point can achieve pure resistance and yield quadrature currents in each dipole. This method of changing the physical dimensions of the antenna element to yield quadrature currents is known as
265:
249:
but actually "cloverleaf shaped", with four small maxima off the ends of the elements. The pattern departs from omnidirectional by only ±5 percent. The radiation in these horizontal directions is often increased by vertically stacking multiple turnstile antennas (called "bays") fed in phase. This
397:
was used for spacecraft (satellite and missile) communication, since circular polarization is not sensitive to the relative orientation of the antennas, and the space vehicle's antenna could have any orientation with respect to the ground antenna. High gain Yagi turnstile antennas were often used
385:
shape of each element produces an antenna with wide impedance bandwidth. Up to eight batwing antennas are usually stacked vertically and fed in phase to make a high gain omnidirectional antenna for TV broadcasting. The wide bandwidth was needed at the low VHF analog TV broadcast band, as the
295:
In a circularly polarized antenna, it is important that the direction of polarization of the transmitting and receiving antennas be the same, since a right-circularly-polarized antenna will suffer a severe loss of gain receiving left-circularly-polarized radio waves, and vice versa.
323:
A popular method of feeding the two dipoles in a turnstile antenna is to split the RF signal from the transmission line into two equal signals with a two way splitter, then delay one by 90 degrees additional electrical length. Each phase is applied to one of the dipoles.
350:
Brown's original patent described stacking multiple turnstile antennas vertically to make a high gain horizontally polarized omnidirectional antenna for radio broadcasting. These were used for some of the first
195:
in New York City for NBC's experimental 46.5 MHz TV station W2XBS in 1939. The cigar-shaped elements gave the antenna a wider bandwidth of 30 MHz necessary for TV transmission.
131:
The turnstile antenna was invented by George Brown in 1935 and described in scholarship in 1936. The patent history reveals the popularity of the turnstile antenna over the years.
355:
antennas in the 1930s. However most modern FM broadcast antennas use circular polarization so the signal strength will not vary with the orientation of the receiver's antenna.
373:
of the antenna. Early TV broadcast antennas used "cigar shaped" elements, shown in image of 1939 RCA Empire State
Building antenna above. A common shape today is the
123:
bands, as circular polarization is often used for satellite communication since it is not sensitive to the orientation of the satellite antenna in space.
315:, meaning the phase of the sine waves must be 90° apart. This is done with feed-line techniques or by adding reactance in series with the dipoles.
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A later innovation involved changing the shape of the dipole elements, from simple rods to broader shapes, to increase the
55:
mounted on the same axis at right angles and fed in quadrature to radiate a narrow beam of circularly polarized radio waves
370:
253:
Since the first turnstiles invented by Brown operated in this mode, the normal mode turnstile is occasionally called the
795:
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Axial mode turnstile antennas are often used for satellite and missile antennas, since circular polarization is used in
78:; the two currents applied to the dipoles are 90° out of phase. The name reflects the notion the antenna looks like a
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144:
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Specialized type of normal mode turnstile antenna used for television broadcasting, called a superturnstile or
31:, consisting of a pair of driven crossed dipoles above a pair passive crossed dipoles serving as a reflector.
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Off the ends of the antenna's axis, perpendicular to the plane of the elements, the antenna radiates
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antennas. Axial mode turnstiles are widely used for satellite ground station antennas in the
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For the antenna to function, the two dipoles must be fed with currents of equal magnitude in
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Another common way to increase the axial mode radiation is to replace each dipole with a
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Whitaker, Jerry (1996). "Antennas for
Specific Applications". In Jerry Whitaker (ed.).
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The turnstile is the earliest and most popular resonant antenna for VHF broadcasting.
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Kraus, John (1988). "16: Antennas for
Special Applications: Feeding Applications".
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48:
44:
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when mounted horizontally. The antenna can be used in two possible modes. In
659:
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47:
turnstile array used to communicate with weather satellites on 136-137 MHz at
571:
983:
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417:
79:
51:, Belgium. Each of the 6 components of the array consists of two 9-element
37:
495:(2nd ed.). Hoboken, New Jersey: John Wiley & Sons, Inc. pp.
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938:
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antenna, used for television broadcasting in the VHF or UHF bands The
1114:
27:
An axial-mode turnstile antenna for 136-137 MHz to receive data from
1093:
264:
704:
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6 MHz TV channel bandwidth was about 10% of the frequency.
178:
708:
424:
Radiation of
Turnstile Antennas Above a Conducting Ground Plane
405:
program made use of the axial mode for telemetry and used the
177:
First turnstile antenna, a normal-mode array built by station
229:
In directions perpendicular to its axis the antenna radiates
245:, a superposition of the two dipole patterns, is close to
487:
Milligan, Thomas (2005). "5 - Dipoles, Slots and Loops".
440:(Subsequent ed.). McGraw-Hill College. p. 892.
418:
Construction plans for ATA(Asymmetric
Turnstile Antenna
269:
Array of 4 axial-mode turnstiles for portable military
237:
when the antenna's axis is vertical). This is called
602:
Brown, George (April 1936). "The
Turnstile Antenna".
181:, Buffalo, NY, in 1936 that broadcast on 41 MHz
1107:
909:
761:
743:
101:Specialized normal mode turnstile antennas called
542:filed: September 20, 1935; granted: July 13, 1937
74:mounted at right angles to each other and fed in
213:The antenna can be used in two different modes:
720:
8:
409:technique to force the quadrature currents.
631:
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577:(2nd ed.). McGraw-Hill, Inc. pp.
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90:radio waves perpendicular to its axis. In
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70:consisting of a set of two identical
7:
618:"Patents about Turnstile Antennas"
281:(CP) radio waves. This is called
66:, or crossed-dipole antenna, is a
14:
1156:Circularly disposed antenna array
974:Folded inverted conformal antenna
684:. CRC Press, Inc. p. 1341.
161:
152:
143:
36:
20:
359:Batwing or superturnstile array
255:George Brown turnstile antenna
1:
1182:Radio frequency antenna types
796:Dielectric resonator antenna
98:radiation along its axis.
660:"[Batwing] Antenna"
638:"[Missile] Antenna"
1203:
436:John Daniel Kraus (1988).
362:
328:Modified dipole dimensions
1059:Regenerative loop antenna
398:for the ground station.
1054:Reflective array antenna
964:Corner reflector antenna
682:The Electronics Handbook
658:Masters, Robert (1945).
954:Collinear antenna array
301:satellite communication
271:satellite communication
113:television broadcasting
1136:Reconfigurable antenna
1099:Yagi–Uda antenna
1074:Short backfire antenna
811:Folded unipole antenna
274:
235:horizontally polarized
187:Normal-mode turnstile
88:horizontally polarized
791:Crossed field antenna
636:Martin, John (1952).
491:Modern Antenna Design
395:Circular polarization
268:
193:Empire State Building
94:the antenna radiates
86:the antenna radiates
43:High gain axial mode
1108:Application-specific
999:Log-periodic antenna
871:Rubber ducky antenna
846:Inverted vee antenna
821:Ground-plane antenna
279:circularly-polarized
96:circularly polarized
1019:Offset dish antenna
866:Random wire antenna
527:"US Patent 2086976"
390:Spacecraft antennas
307:Feeding the antenna
1161:Television antenna
1009:Microstrip antenna
949:Choke ring antenna
944:Cassegrain antenna
841:Inverted-F antenna
753:Isotropic radiator
275:
231:linearly polarized
29:weather satellites
1169:
1168:
1146:Reference antenna
1039:Parabolic antenna
959:Conformal antenna
881:Turnstile antenna
776:Biconical antenna
506:978-0-471-45776-3
454:Turnstile Antenna
447:978-0-070-35422-7
335:turnstile feeding
243:radiation pattern
64:turnstile antenna
1194:
1187:Antennas (radio)
1120:Corner reflector
934:Beverage antenna
896:Umbrella antenna
861:Monopole antenna
816:Franklin antenna
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76:phase quadrature
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1126:Evolved antenna
1103:
1089:Vivaldi antenna
1064:Rhombic antenna
989:Helical antenna
979:Fractal antenna
924:AS-2259 Antenna
905:
836:Helical antenna
806:Discone antenna
786:Coaxial antenna
771:Batwing antenna
763:Omnidirectional
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407:modified dipole
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365:Batwing antenna
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353:FM broadcasting
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319:Quadrature feed
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247:omnidirectional
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203:batwing antenna
189:(lower antenna)
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135:Characteristics
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72:dipole antennas
60:
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11:
5:
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1084:Sterba antenna
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1044:Plasma antenna
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919:Adcock antenna
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876:Sloper antenna
873:
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851:J-pole antenna
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531:Antenna system
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456:, pp. 726-729.
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413:External links
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379:superturnstile
363:Main article:
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346:Stacked arrays
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68:radio antenna
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53:Yagi antennas
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23:
1079:Slot antenna
1049:Quad antenna
1034:Planar array
1029:Phased array
1004:Loop antenna
994:Horn antenna
901:Whip antenna
886:T2FD antenna
880:
831:Halo antenna
826:G5RV antenna
695:
681:
675:
663:. Retrieved
653:
641:. Retrieved
612:
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534:. Retrieved
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430:Bibliography
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403:Nike missile
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341:Applications
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111:are used as
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61:
929:AWX antenna
911:Directional
781:Cage aerial
604:Electronics
239:normal mode
225:Normal mode
215:normal mode
84:normal mode
1176:Categories
665:15 January
643:15 January
536:14 January
461:References
290:Yagi array
283:axial mode
261:Axial mode
219:axial mode
92:axial mode
1122:(passive)
984:Gizmotchy
891:T-antenna
745:Isotropic
452:$ 16-7:
371:bandwidth
80:turnstile
1141:Rectenna
939:Cantenna
573:Antennas
438:Antennas
273:terminal
185:(center)
736:Antenna
401:The US
383:batwing
375:batwing
241:. The
199:(right)
191:on the
127:History
1115:ALLISS
688:
585:
581:–729.
503:
499:–237.
444:
175:(left)
1094:WokFi
738:types
292:.
686:ISBN
667:2014
645:2014
583:ISBN
538:2014
501:ISBN
442:ISBN
217:and
179:W8XH
119:and
49:Redu
45:Yagi
579:726
497:231
377:or
121:UHF
117:VHF
105:or
1178::
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626:^
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62:A
728:e
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714:v
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Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
