78:
301:
221:
reflector wire is hung between two insulators and doesn't make contact with any other objects. It can be mounted a few inches above the ground or at a maximum height of 10 feet (or 3 meters) above the soil. This height allows for convenient lawn mowing without any disruptions. Essentially, this antenna consists of a 2-element beam that is oriented vertically.
216: wave. That proximity to the ground forces the majority of the radiation to go straight up, causing NVIS propagation to occur. The overall efficiency of the antenna can be increased by placing a ground wire, slightly longer than the antenna, parallel to and directly underneath the antenna. A single ground wire can provide antenna
132:. Another interesting aspect of NVIS communication is that direction finding of the sender is more difficult than for ground-wave communication (i.e. VHF or UHF). For broadcasters, NVIS allows coverage of an entire medium-sized country at much lower cost than with VHF (FM), and daytime coverage, similar to
291:
wavelength above ground, or arrays of such dipoles. Up to 16 dipoles can be used, allowing strong signals with relatively low power by concentrating the signal in a smaller receiving area. Limiting the coverage may be dictated by licensing, language, or political considerations. Arrays of dipoles
87:
The most reliable frequencies for NVIS communications are between 1.8 MHz and 8 MHz. Above 8 MHz, the probability of success begins to decrease, dropping to near zero at 30 MHz. Usable frequencies are dictated by local ionospheric conditions, which have a strong systematic
220:
in the 3β6 dB range. This is a reflector element used to form a 2-element Yagi beam antenna. The wire length for the reflector element is 5% longer than the dipole-driven element positioned above it. The dipole is located at a distance of 0.15 wavelengths above the reflector element. The
568:
Barker, G.E.; Taylor, J.; Hagn, G.H. (December 1971). Summary of measurements and modeling of the radiation patterns of simple field antennas in open (level) terrain, mountains and forests (Report). Aberdeen, MD: U.S. Army
Electronic Command, Aberdeen Proving Ground. Spec. Tech.
103:
Optimum NVIS frequencies tend to be higher towards the tropics and lower towards the arctic regions. They are also higher during high sunspot activity years. The usable frequencies change from day to night, because sunlight causes the lowest layer of the ionosphere, called the
68:
There is no fundamental difference between NVIS and conventional skywave propagation; the practical distinction arises solely from different desirable radiation patterns of the antennas (near vertical for NVIS, near horizontal for conventional long-range skywave propagation).
292:
can be used to "slew" the pattern so that the transmitter need not be in the center of the coverage footprint. Broadcast NVIS antennas usually use an extensive ground screen to increase gain and stabilize the pattern and feed impedance with changing ground moisture.
224:
Another source indicates 2 dB for a single wire and nearly 4 dB for multiple ground wires. Ground wires are more necessary when using lower dipoles over poor soils as without them considerable energy goes into heat and not the radio waves.
271:
Significant increases in communication will obviously be realized when both the transmitting station and the receiving station use NVIS configuration for their antennas. In particular, for low profile operations, NVIS antennas are a good option.
112:
rises with greater sunlight. Real-time maps of the critical frequency are available. Use of a frequency about 15% below the critical frequency should provide reliable NVIS service. This is sometimes referred to as the
268: wavelength on receive, according to military sources and an extensive study by Dutch researchers. Very low antennas are far more inferior on both transmit and receive, where noise and signal are attenuated.
581:
57:
back down and can be received within a circular region up to 650 km (400 miles) from the transmitter. If the frequency is too high (that is, above the critical frequency of the ionospheric
691:
88:
dependence on geographical location. Common bands used in amateur radio at mid-latitudes are 3.5 MHz at night and 7 MHz during daylight, with experimental use of 5 MHz (
332:
International Radio
Consultative Committee (1969). Broadcasting in Band 7 (HF) in the Tropical Zone (Report). Geneva, CH: International Telecommunications Union.
408:
41:
radio-wave propagation path that provides usable signals in the medium distances range β usually 0β650 km (0β400 miles). It is used for military and
620:
815:
580:
Witvliet, Ben A.; van Maanen, Erik; Petersen, George J.; Westenberg, Albert J.; Bentum, Mark J.; Slump, Cornelis H.; Schiphorst, Roel (February 2015).
83:
While the groundwave (blue) cannot propagate, the refracted skywaves (red) achieve HF coverage within the common first hop (~500 km or 310 miles).
128:(or the terrain is so rugged and barren that groundwave is not effective), and less than the 500β2,400 km (300β1,500 miles) range of lower-angle
108:, to increase, causing attenuation of low frequencies during the day while the maximum usable frequency (MUF) which is the critical frequency of the
931:
766:
496:
17:
684:
100:
between 3.9 and 6.2 MHz. Military NVIS communications mostly take place on 2β4 MHz at night, and 5β7 MHz during daylight.
92:) frequencies. During winter nights at the bottom of the sunspot cycle, the 1.8 MHz band may be required. Broadcasting uses the
651:
144:
An NVIS antenna configuration is a horizontally polarized (parallel with the surface of the earth) radiating element that is from
842:
1302:
409:"An analytical study of HF communications between provincial PREOC-s and the North Shore Emergency Management office at VE7NSR"
724:
523:
443:
312:: The four dipole wires also serve as guy wire for the antenna mast. An alternative configuration consists of a transmitting
344:
1307:
547:
582:"Near vertical incidence skywave propagation: Elevation angles and optimum antenna height for horizontal dipole antennas"
1271:
1089:
114:
387:
419:
49:
for nearby contacts circumventing line-of-sight barriers. The radio waves travel near-vertically upwards into the
471:
61:), refraction is insufficient to return the signal to earth and if it is too low, absorption in the ionospheric
785:
515:
911:
936:
835:
579:
1312:
1174:
121:
1169:
1079:
1069:
878:
124:
is ineffective, or when the communication distance is beyond the 80 km (50 miles) range of
1251:
1189:
926:
828:
125:
906:
760:
236:) can be used for NVIS communication, with horizontal dipoles or inverted V dipoles at about
1214:
1114:
986:
961:
748:
739:
Wedgwood, Antony (G0TJD); Goldstein, J.A. (April 2001). "Near vertical incidence skywave".
596:
200: wavelength, and high angle radiation declines only slightly for heights up to about
8:
1297:
1134:
1026:
981:
308:
One popular military NVIS antenna is the AS-2259 Antenna, which consists of two V-shaped
752:
600:
1276:
1124:
1064:
1059:
956:
868:
644:
612:
217:
1261:
1154:
1074:
996:
891:
720:
519:
490:
616:
1235:
1049:
1011:
976:
604:
1241:
1204:
1179:
1104:
1094:
951:
921:
901:
886:
851:
355:
97:
93:
1266:
1199:
1184:
1159:
1034:
991:
966:
916:
800:
539:
309:
252: wavelength above ground giving the best results on transmit and at about
233:
46:
774:
Walden, M. (March 2008). "Extraordinary wave NVIS propagation at 5 MHz".
1291:
1246:
1139:
1129:
1084:
971:
608:
89:
810:
184: wave above the ground. The optimum height of such an antenna is about
1194:
1164:
1149:
1144:
1119:
1109:
1016:
1001:
946:
941:
313:
42:
719:. Potters Bar, UK: Radio Society of Great Britain. pp. 33β34, 64β65.
331:
1044:
896:
379:
77:
738:
228:
Depending on the specific requirements, various antennas (i.e. Sloper,
161:
133:
50:
460:
1099:
1006:
54:
1256:
1054:
860:
136:
nighttime coverage at lower cost and often with less interference.
805:
633:– via Radiocommunications Agency Netherlands, Groningen, NL.
129:
109:
105:
62:
58:
38:
820:
45:
communications, broadcasting, especially in the tropics, and by
1230:
776:
811:
Make A Quick, Easy, Cheap, NVIS Antenna for
Roadside Operating
1209:
316:
which is configured for maximum signal transmission upwards.
275:
For broadcasting, typical antennas consist of a dipole about
229:
300:
165:
741:
The
Vintage and Military Amateur Radio Society Newsletter
448:. Bureau of Meteorology (map). Commonwealth of Australia.
1289:
567:
120:NVIS is most useful in mountainous areas where
518:. pp. 61, 89β90, 109β110, 126, 143, 154.
72:
836:
690:(Report). 1986. AS-2259, TM11-5985-379-14P.
765:: CS1 maint: numeric names: authors list (
495:: CS1 maint: numeric names: authors list (
843:
829:
773:
1039:
299:
76:
14:
1290:
714:
589:IEEE Antennas and Propagation Magazine
509:
477:from the original on 21 September 2017
345:"The emergency communications antenna"
824:
717:Technical Topics Scrapbook 1990β1994
512:Technical Topics Scrapbook 2000β2004
96:between 2.3β5.06 MHz, and the
24:
295:
25:
1324:
1272:Circularly disposed antenna array
1090:Folded inverted conformal antenna
850:
794:
458:
342:
115:optimum working frequency or FOT
65:may reduce the signal strength.
708:
697:from the original on 2018-02-19
677:
674:Broadcasting in Bandβ―7, pageβ―39
668:
657:from the original on 2015-06-03
645:"Space challenged NVIS antenna"
637:
573:
550:from the original on 2018-09-09
390:from the original on 2017-12-01
380:"Real-time local NVIS & DX"
31:Near vertical incidence skywave
18:Near Vertical Incidence Skywave
786:Radio Society of Great Britain
561:
532:
516:Radio Society of Great Britain
503:
452:
436:
401:
372:
336:
325:
27:Type of radio-wave propagation
13:
1:
1303:Radio frequency antenna types
319:
98:international broadcast bands
912:Dielectric resonator antenna
418:. March 2010. Archived from
7:
1308:Radio frequency propagation
139:
73:Frequencies and propagation
10:
1329:
801:Analysis of height vs gain
343:Finch, Stephen C. (AIΓW).
1223:
1175:Regenerative loop antenna
1025:
877:
859:
134:mediumwave (AM broadcast)
122:line-of-sight propagation
1170:Reflective array antenna
1080:Corner reflector antenna
609:10.1109/MAP.2015.2397071
94:tropical broadcast bands
1070:Collinear antenna array
81:NVIS radiation pattern
1252:Reconfigurable antenna
1215:Yagi–Uda antenna
1190:Short backfire antenna
927:Folded unipole antenna
784:(3). Potters Bar, UK:
305:
84:
907:Crossed field antenna
445:World ionospheric map
303:
80:
1224:Application-specific
1115:Log-periodic antenna
987:Rubber ducky antenna
962:Inverted vee antenna
937:Ground-plane antenna
806:QSL.net NVIS Article
715:Hawker, Pat (1999).
510:Hawker, Pat (2005).
304:AS-2259 NVIS antenna
130:sky-wave propagation
1135:Offset dish antenna
982:Random wire antenna
753:1995nrl..reptS....W
601:2015IAPM...57..129W
514:. Potters Bar, UK:
461:"Planning antennas"
459:Brown, Jim (K9YC).
1277:Television antenna
1125:Microstrip antenna
1065:Choke ring antenna
1060:Cassegrain antenna
957:Inverted-F antenna
869:Isotropic radiator
306:
85:
1285:
1284:
1262:Reference antenna
1155:Parabolic antenna
1075:Conformal antenna
997:Turnstile antenna
892:Biconical antenna
726:978-1-872309-51-4
525:978-1-905086-05-4
53:, where they are
16:(Redirected from
1320:
1313:Antennas (radio)
1236:Corner reflector
1050:Beverage antenna
1012:Umbrella antenna
977:Monopole antenna
932:Franklin antenna
845:
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619:. Archived from
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354:. Archived from
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1323:
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1318:
1317:
1288:
1287:
1286:
1281:
1242:Evolved antenna
1219:
1205:Vivaldi antenna
1180:Rhombic antenna
1105:Helical antenna
1095:Fractal antenna
1040:AS-2259 Antenna
1021:
952:Helical antenna
922:Discone antenna
902:Coaxial antenna
887:Batwing antenna
879:Omnidirectional
873:
855:
849:
797:
792:
758:
757:
734:
727:
713:
709:
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623:
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540:"NVIS antennas"
538:
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508:
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488:
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463:
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393:
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296:AS-2259 antenna
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82:
75:
28:
23:
22:
15:
12:
11:
5:
1326:
1316:
1315:
1310:
1305:
1300:
1283:
1282:
1280:
1279:
1274:
1269:
1267:Spiral antenna
1264:
1259:
1254:
1249:
1244:
1239:
1233:
1227:
1225:
1221:
1220:
1218:
1217:
1212:
1207:
1202:
1200:Sterba antenna
1197:
1192:
1187:
1185:Sector antenna
1182:
1177:
1172:
1167:
1162:
1160:Plasma antenna
1157:
1152:
1147:
1142:
1137:
1132:
1127:
1122:
1117:
1112:
1107:
1102:
1097:
1092:
1087:
1082:
1077:
1072:
1067:
1062:
1057:
1052:
1047:
1042:
1037:
1035:Adcock antenna
1031:
1029:
1023:
1022:
1020:
1019:
1014:
1009:
1004:
999:
994:
992:Sloper antenna
989:
984:
979:
974:
969:
967:J-pole antenna
964:
959:
954:
949:
944:
939:
934:
929:
924:
919:
917:Dipole antenna
914:
909:
904:
899:
894:
889:
883:
881:
875:
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871:
865:
863:
857:
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848:
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819:
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808:
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796:
795:External links
793:
791:
790:
771:
735:
733:
732:
725:
707:
685:Antenna Manual
676:
667:
636:
595:(1): 129β146.
572:
560:
531:
524:
502:
451:
435:
400:
371:
335:
323:
321:
318:
297:
294:
141:
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74:
71:
47:radio amateurs
26:
9:
6:
4:
3:
2:
1325:
1314:
1311:
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1248:
1247:Ground dipole
1245:
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1234:
1232:
1229:
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1222:
1216:
1213:
1211:
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1153:
1151:
1148:
1146:
1143:
1141:
1140:Patch antenna
1138:
1136:
1133:
1131:
1130:Moxon antenna
1128:
1126:
1123:
1121:
1118:
1116:
1113:
1111:
1108:
1106:
1103:
1101:
1098:
1096:
1093:
1091:
1088:
1086:
1085:Curtain array
1083:
1081:
1078:
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1063:
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973:
972:Mast radiator
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948:
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839:
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827:
826:
823:
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816:NVIS tutorial
814:
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626:on 2017-04-11
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569:Rep. 45.
564:
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498:
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469:
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425:on 2016-03-03
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389:
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381:
375:
361:on 2019-09-20
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66:
64:
60:
56:
52:
48:
44:
40:
36:
32:
19:
1195:Slot antenna
1165:Quad antenna
1150:Planar array
1145:Phased array
1120:Loop antenna
1110:Horn antenna
1017:Whip antenna
1002:T2FD antenna
947:Halo antenna
942:G5RV antenna
781:
775:
761:cite journal
744:
740:
716:
710:
699:. Retrieved
679:
670:
659:. Retrieved
639:
628:. Retrieved
621:the original
592:
588:
575:
563:
552:. Retrieved
543:
534:
511:
505:
479:. Retrieved
467:
454:
444:
438:
427:. Retrieved
420:the original
415:
403:
392:. Retrieved
384:hamwaves.com
383:
374:
363:. Retrieved
356:the original
351:
338:
327:
314:loop antenna
307:
274:
270:
227:
223:
143:
119:
102:
86:
67:
43:paramilitary
34:
30:
29:
1045:AWX antenna
1027:Directional
897:Cage aerial
1298:Ionosphere
1292:Categories
701:2018-03-09
661:2012-12-29
630:2017-04-10
554:2013-06-25
429:2012-12-29
394:2017-11-23
365:2012-12-29
320:References
162:wavelength
126:groundwave
51:ionosphere
1238:(passive)
1100:Gizmotchy
1007:T-antenna
861:Isotropic
55:refracted
1257:Rectenna
1055:Cantenna
788:: 57β62.
747:: 7β11.
692:Archived
652:Archived
617:36138456
548:Archived
544:w8ji.com
491:cite web
481:30 April
472:Archived
468:k9yc.com
416:nsarc.ca
388:Archived
352:w8ne.com
160:th
140:Antennas
852:Antenna
749:Bibcode
597:Bibcode
310:dipoles
289:
277:
266:
254:
250:
238:
214:
202:
198:
186:
182:
170:
158:
146:
110:F layer
106:D layer
63:D layer
59:F layer
39:skywave
37:, is a
1231:ALLISS
777:RadCom
723:
615:
522:
234:Dipole
1210:WokFi
854:types
695:(PDF)
688:(PDF)
655:(PDF)
648:(PDF)
624:(PDF)
613:S2CID
585:(PDF)
475:(PDF)
464:(PDF)
423:(PDF)
412:(PDF)
359:(PDF)
348:(PDF)
168:) to
33:, or
767:link
721:ISBN
520:ISBN
497:link
483:2017
230:T2FD
218:gain
90:60 m
35:NVIS
605:doi
155:20
117:.
1294::
782:84
780:.
763:}}
759:{{
745:16
743:.
650:.
611:.
603:.
593:57
591:.
587:.
546:.
542:.
493:}}
489:{{
470:.
466:.
414:.
386:.
382:.
350:.
280:1
257:1
241:1
232:,
205:3
189:1
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