1111:" is slightly shorter than a half-wavelength; it serves to increase the radiation in a given direction. A Yagi antenna may have a reflector on one side of the driven element, and one or more directors on the other side. If all the elements are in a plane, usually only one reflector is used, because additional ones give little improvement in gain, but sometimes additional reflectors are mounted above and below the plane of the antenna on a vertical bracket at the end.
148:
1115:
934:
697:
42:
77:
1149:
is sometimes mounted above another driven patch antenna. This antenna combination resonates at a slightly lower frequency than the original element. However, the main effect is to greatly increase the impedance bandwidth of the antenna. In some cases the bandwidth can be increased by a factor of 10.
1122:
reception with 22 parasitic elements; 4 reflectors attached to the vertical bracket at left, and 18 directors attached to the horizontal beam at right. The driven element is attached to the black box next to the reflectors. The antenna is most sensitive to radio waves coming from the
1091:
The parasitic elements in a Yagi antenna are mounted parallel to the driven element, with all the elements usually in a line perpendicular to the direction of radiation of the antenna. What effect a parasitic element has on the radiation pattern depends both on its separation from the next element,
1127:
All the elements are usually mounted on a metal beam or bracket along the antenna's central axis. Although sometimes the parasitic elements are insulated from the supporting beam, often they are clamped or welded directly to it, electrically connected to it. This doesn't affect their functioning,
873:
elements of decreasing length, all of which are driven. However, because they are different lengths, only one of the many dipoles is resonant at a given frequency, so only one is driven at a time. The dipole that is driven depends on the
893:
generally consist of a hybrid between a UHF Yagi with one driven dipole and a log-periodic for VHF behind that with alternating active elements. The driven elements between the UHF and VHF are then coupled and often
1141:
over the dipole. Adding a director to this, to give a 3 element Yagi, gives a gain of about 7 dB over a dipole. As a rule of thumb, each additional parasitic element beyond this adds about 1 dB of gain.
1137:
The addition of parasitic elements gives a diminishing improvement in the antenna's gain. Adding a reflector to a dipole, to make a 2 element Yagi, increases the gain by about 5
800:
current from the transmitter, and is the source of the radio waves. In a receiving antenna it collects the incoming radio waves for reception, and converts them to tiny oscillating
835:
An antenna may have more than one driven element, although the most common multielement antenna, the Yagi, usually has only one. For example, transmitting antennas for AM
951:
718:
1154:
922:
364:
1080:, something like a guitar's sound box, absorbing the radio waves from the nearby driven element and re-radiating them again with a different
370:
998:
567:
359:
970:
1214:
1042:
is a conductive element, typically a metal rod, which is not electrically connected to anything else. Multielement antennas such as the
382:
1255:
629:
977:
1224:
1017:
744:
808:. Multielement antennas like the Yagi typically consist of a driven element, connected to the receiver or transmitter through a
1085:
984:
955:
722:
1107:" is slightly longer (around 5%) than a half-wavelength. It serves to reflect the radio waves in the opposite direction. A "
1165:
is similar in appearance to a Yagi, but all of its elements are driven elements, connected to the transmitter or receiver.
966:
493:
245:
905:
When a "driven element" is referred to in an antenna array, it is often assumed that other elements are not driven (i.e.
1088:, strengthening the antenna's radiation in the desired direction, and cancelling out the waves in undesired directions.
230:
1247:
1068:
of the radio waves emitted by the driven element, directing them in a beam in one direction, increasing the antenna's
483:
707:
320:
28:
944:
726:
711:
1274:
473:
52:
used for analog channels 2–4, 54–72 MHz (U.S. channels). It has four parasitic elements: three directors (
648:
991:
622:
584:
330:
518:
375:
1043:
769:
80:
1162:
1128:
because the RF voltage distribution along the element is maximum at the ends and goes to zero (has a
895:
866:
503:
46:
35:
147:
890:
844:
463:
423:
265:
190:
49:
1064:, and parasitic elements, which are not. The purpose of the parasitic elements is to modify the
1185:
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1153:
1093:
1065:
858:
851:
825:
813:
615:
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220:
131:
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is the element in the antenna (typically a metal rod) which is electrically connected to the
906:
847:
801:
758:
310:
255:
250:
180:
797:
589:
315:
260:
170:
139:
854:. A two-element array with the elements spaced a quarter wavelength apart has a distinct
1157:
Comparison of a Yagi with parasitic elements to a log periodic, with all active elements
1130:
1096:
1053:
1048:
870:
817:
805:
781:
668:
513:
478:
433:
185:
165:
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1031:
862:
840:
836:
765:
644:
543:
305:
275:
225:
157:
92:
61:
1161:
Not all types of thin conductor multielement antennas have parasitic elements. The
1145:
In an example of a parasitic element that is not rod-shaped, a parasitic microstrip
41:
34:"Parasitic element" redirects here. For unwanted electrical circuit components, see
1073:
883:
829:
488:
413:
300:
235:
195:
175:
1114:
757:"Active element" redirects here. For the devices used in electronic circuits, see
17:
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1057:
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and couple electromagnetically with the driven element, and serve to modify the
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696:
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418:
280:
240:
112:
69:
921:"Parasitic element" redirects here. For the unwanted circuit elements, see
828:
of the antenna, directing the radio waves in one direction, increasing the
115:
leading to the receiver is not shown; it attaches to the driven element at
76:
855:
340:
1138:
1103:
of the radio waves used. The parasitic elements are of two types. A "
1119:
879:
1113:
1092:
and on its length. The driven element of the antenna is usually a
861:
when the second element is driven with a source −90° out of
598:
335:
325:
215:
75:
40:
27:"Passive radiator" redirects here. For the speaker enclosure, see
576:
927:
812:, and a number of other elements which are not driven, called
690:
123:. The antenna radiates radio waves in a beam toward the right.
909:) and that the array is tightly coupled (spacing far below a
1076:). A parasitic element does this by acting as a passive
1134:) at the midpoint where the grounded beam is attached.
1216:
958:. Unsourced material may be challenged and removed.
1084:. The waves from the different antenna elements
886:may have hundreds of driven elements. Household
95:, and 5 parasitic elements: one reflector (
623:
72:feedline down the mast to the television set.
8:
725:. Unsourced material may be challenged and
630:
616:
126:
1018:Learn how and when to remove this message
745:Learn how and when to remove this message
1208:
1206:
1152:
1176:
923:parasitic element (electrical networks)
850:driven element, to create a particular
138:
1123:right, parallel to the antenna's axis.
365:Wireless electronic devices and health
577:Multiple-input multiple-output (MIMO)
371:International Telecommunication Union
7:
956:adding citations to reliable sources
723:adding citations to reliable sources
396:Radiation sources / regions
360:Wireless device radiation and health
60:) and one driven element which is a
788:. In a transmitting antenna it is
667:) is electrically connected to the
651:elements (typically metal rods), a
383:World Radiocommunication Conference
902:coaxial downlead to the receiver.
25:
865:relative to the first element. A
932:
820:. The parasitic elements act as
816:. The driven element is often a
695:
146:
967:"Driven and parasitic elements"
943:needs additional citations for
843:, each of which functions as a
1250:. 2015. Subsection 11.1.
1246:(23 ed.). Newington, CT:
1219:. Elsevier. pp. 102–191.
1:
246:Low-noise block downconverter
1052:" which is connected to the
231:Counterpoise (ground system)
68:) connected to a 300 Ω
1248:American Radio Relay League
804:, which are applied to the
484:Friis transmission equation
1291:
920:
756:
321:Municipal wireless network
33:
29:Passive radiator (speaker)
26:
1229:– via Google Books.
839:often consist of several
568:Bell Laboratories Layered
83:with one driven element (
1046:typically consist of a "
869:(LPDA) consists of many
103:) and 4 directors (
601:Multiple Access (WSDMA)
599:Wideband Space Division
1192:. Adrio Communications
1158:
1124:
331:Radio masts and towers
124:
73:
45:Drawing of a Yagi–Uda
1190:Radio-Electronics.com
1156:
1117:
519:Signal-to-noise ratio
354:Safety and regulation
79:
56:) and one reflector (
44:
1163:log periodic antenna
1099:, its length half a
952:improve this article
867:log-periodic antenna
719:improve this section
504:Radiation resistance
1213:Poole, Ian (2003).
1184:Poole, Ian (2010).
891:television antennas
36:parasitic impedance
1186:"The Yagi Antenna"
1159:
1125:
917:Parasitic elements
907:parasitic, passive
814:parasitic elements
764:In a multielement
570:Space-Time (BLAST)
424:Near and far field
125:
74:
50:television antenna
1244:ARRL Antenna Book
1118:Yagi antenna for
1066:radiation pattern
1036:parasitic element
1028:
1027:
1020:
1002:
859:radiation pattern
852:radiation pattern
826:radiation pattern
802:electric currents
755:
754:
747:
677:parasitic element
647:made of multiple
640:
639:
524:Spurious emission
509:Radio propagation
499:Radiation pattern
474:Equivalent radius
469:Electrical length
376:Radio Regulations
221:Block upconverter
18:Parasitic element
16:(Redirected from
1282:
1275:Antennas (radio)
1261:
1231:
1230:
1210:
1201:
1200:
1198:
1197:
1181:
1044:Yagi–Uda antenna
1040:passive radiator
1023:
1016:
1012:
1009:
1003:
1001:
960:
936:
928:
832:of the antenna.
770:Yagi–Uda antenna
759:Active component
750:
743:
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736:
730:
699:
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681:passive radiator
632:
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397:
311:Cellular network
251:Passive radiator
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1237:Further reading
1234:
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798:radio frequency
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751:
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689:
687:Driven elements
665:active radiator
661:driven radiator
642:
636:
607:
606:
603:
600:
594:
590:Spread spectrum
585:Reconfiguration
572:
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447:Characteristics
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1257:978-1625950444
1256:
1238:
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1233:
1232:
1225:
1202:
1175:
1173:
1170:
1054:radio receiver
1049:driven element
1026:
1025:
940:
938:
931:
918:
915:
898:for a 75
841:mast radiators
837:radio stations
778:active element
774:driven element
753:
752:
703:
701:
694:
688:
685:
657:active element
653:driven element
638:
637:
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634:
627:
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514:Radio spectrum
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434:Vertical plane
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186:Satellite dish
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1226:0-7506-5612-3
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1203:
1191:
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1171:
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1147:patch antenna
1143:
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1135:
1133:
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1032:radio antenna
1022:
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1008:December 2009
1000:
997:
993:
990:
986:
983:
979:
976:
972:
969: –
968:
964:
963:Find sources:
957:
953:
947:
946:
941:This article
939:
935:
930:
929:
924:
916:
914:
912:
908:
903:
901:
897:
892:
889:
885:
884:Phased arrays
881:
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872:
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860:
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853:
849:
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842:
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833:
831:
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815:
811:
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799:
795:
791:
787:
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771:
767:
766:antenna array
760:
749:
746:
738:
728:
724:
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714:
713:
709:
704:This section
702:
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693:
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686:
684:
682:
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666:
662:
659:(also called
658:
654:
650:
646:
645:antenna array
633:
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621:
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583:
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544:Beam steering
542:
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507:
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306:Amateur radio
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226:Coaxial cable
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93:folded dipole
90:
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63:
62:folded dipole
59:
55:
51:
48:
43:
37:
30:
19:
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1215:
1194:. Retrieved
1189:
1179:
1167:
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1144:
1136:
1129:
1126:
1108:
1104:
1090:
1047:
1039:
1035:
1029:
1014:
1005:
995:
988:
981:
974:
962:
950:Please help
945:verification
942:
904:
834:
793:
789:
777:
773:
763:
741:
732:
717:Please help
705:
680:
676:
664:
660:
656:
652:
641:
414:Ground plane
301:Antenna farm
158:Common types
116:
104:
96:
84:
81:Yagi antenna
65:
57:
53:
1070:directivity
1058:transmitter
786:transmitter
768:(such as a
673:transmitter
554:Beamforming
459:Directivity
409:Focal cloud
271:Transmitter
91:) called a
1196:2011-03-29
1172:References
1101:wavelength
1060:through a
978:newspapers
911:wavelength
822:resonators
735:April 2016
683:) is not.
649:conductive
559:Small cell
537:Techniques
464:Efficiency
454:Array gain
209:Components
191:Television
66:double rod
1105:reflector
1094:half-wave
1086:interfere
1078:resonator
1062:feed line
888:multiband
876:frequency
845:half-wave
810:feed line
706:does not
549:Beam tilt
429:Side lobe
419:Main lobe
404:Boresight
281:Twin-lead
241:Feed line
113:feed line
70:twin lead
1269:Category
1109:director
856:cardioid
848:monopole
806:receiver
782:receiver
675:while a
669:receiver
575:Massive
341:Wireless
256:Receiver
181:Monopole
140:Antennas
132:a series
130:Part of
111:). The
58:to right
992:scholar
896:matched
878:of the
796:by the
794:excited
772:), the
727:removed
712:sources
316:Hotspot
294:Systems
261:Rotator
171:Fractal
54:to left
1254:
1223:
1120:UHF TV
1097:dipole
994:
987:
980:
973:
965:
880:signal
871:dipole
818:dipole
790:driven
643:In an
494:Height
479:Factor
166:Dipole
1082:phase
1030:In a
999:JSTOR
985:books
863:phase
336:Wi-Fi
326:Radio
276:Tuner
216:Balun
1252:ISBN
1221:ISBN
1131:node
1074:gain
1034:, a
971:news
830:gain
710:any
708:cite
679:(or
489:Gain
266:Stub
236:Feed
196:Whip
176:Loop
1056:or
1038:or
954:by
913:).
792:or
784:or
776:or
721:by
671:or
663:or
655:or
47:VHF
1271::
1205:^
1188:.
1139:dB
882:.
134:on
1260:.
1199:.
1072:(
1021:)
1015:(
1010:)
1006:(
996:·
989:·
982:·
975:·
948:.
925:.
900:Ω
761:.
748:)
742:(
737:)
733:(
729:.
715:.
631:e
624:t
617:v
378:)
374:(
119:D
107:C
99:B
87:A
64:(
38:.
31:.
20:)
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