1109:
1117:
20:
1192:(VLF) range, for transcontinental wireless communication. A typical alternator with an output frequency of 100 kHz had 300 poles and rotated at 20,000 revolutions per minute (RPM) (333 revolutions per second). To produce high power, the clearance between the rotor and stator had to be kept to only 1 mm. The manufacture of precision machines rotating at such high speeds presented many new problems, and Alexanderson transmitters were bulky and very expensive.
161:
1210:
produce a feedback signal to control the motor speed. If the output frequency gets too high, the impedance presented by the LC circuit increases, and the amplitude of the RF signal getting through the LC circuit drops. The feedback signal to the motor drops, and the motor slows down. Thus the alternator output frequency is "locked" to the tuned circuit resonant frequency.
1125:
with narrow slots cut in its circumference to create a series of narrow "teeth" that function as magnetic poles. The space between the teeth is filled with nonmagnetic material, to give the rotor a smooth surface to decrease aerodynamic drag. The rotor is turned at a high speed by an electric motor through a speed–increaser gearbox.
1281:
Other major problems were that changing the operating frequency was a lengthy and complicated process, and unlike a spark transmitter, the carrier signal could not be switched on and off at will. The latter problem greatly complicated "listening through" (that is, stopping the transmission to listen
1124:
The
Alexanderson alternator works similarly to an AC electric generator, but generates higher-frequency current, in the very low frequency (VLF) radio frequency range. The rotor has no conductive windings or electrical connections; it consists of a solid disc of high tensile strength magnetic steel,
1148:
As the rotor turns, alternately either an iron section of the disk is in the gap between each pair of stator poles, allowing a high magnetic flux to cross the gap, or else a non-magnetic slot is in the stator gap, allowing less magnetic flux to pass. Thus the magnetic flux through the stator varies
1095:
During World War II the U.S. Navy recognized the need for reliable distant longwave (VLF) transmissions to the
Pacific fleet. A new facility was constructed at Haiku in Hawaii, where two 200 KW Alexanderson alternators transferred from the mainland were installed. The Navy also operated an existing
1099:
In the late 1940s the Air Force assumed control of the Haiku and Marion, Massachusetts facilities. The Air Force found that longwave transmissions were more reliable than shortwave when sending weather information to Arctic researchers as well as bases in
Greenland, Labrador, and Iceland. The two
1222:
A large
Alexanderson alternator might produce 500 kW of output radio-frequency energy and would be water- or oil-cooled. One such machine had 600 pole pairs in the stator winding, and the rotor was driven at 2170 RPM, for an output frequency near 21.7 kHz. To obtain higher frequencies,
1213:
The sets were built to operate at wavelengths of 10,500 to 24,000 meters (28.57 to 12.5 kHz). This was accomplished by three design variables. The alternators were built with 1220, 976 or 772 poles. Three gearboxes were available with ratios of 2.675, 2.973 and 3.324 and the 900 RPM driving
1273:
Because of the extremely high rotational speed compared to a conventional alternator, the
Alexanderson alternator required continuous maintenance by skilled personnel. Efficient lubrication and oil or water cooling was essential for reliability which was difficult to achieve with the lubricants
1209:
is slightly above the output frequency. The generator's frequency falls on the "skirt" of the LC circuit's impedance curve, where the impedance increases rapidly with frequency. The output of the LC circuit is rectified, and the resulting voltage is compared with a constant reference voltage to
1628:
by Thorn L. Mayes, The New
England Wireless and Steam Museum, Inc., 1989, page 182. Includes the note "Call letters and wave lengths in meters from RCA listing Long Wave Stations, Dec. 5, 1928". The "Frequency" column has been added, using 300,000 meters/second as the speed-of-light for the
259:
forced
European nations to temporarily abandon development of international radio communications networks, while the United States increased efforts to develop transoceanic radio. By the end of the war the Alexanderson alternator was operating to reliably provide transoceanic radio service.
1353:
Nowadays, it would be technically possible to construct an
Alexanderson alternator operating at higher frequencies (for instance, an Alexanderson alternator with a 10,000-pole rotor spinning at 300,000 RPM would produce a transmission frequency of 50 MHz, into the lower portion of the
1242:. These were electrically "noisy"; the energy of the transmitter was spread over a wide frequency range, so they interfered with other transmissions and operated inefficiently. With a continuous-wave transmitter, all of the energy was concentrated within a narrow
1200:
The output frequency of the transmitter is proportional to the speed of the rotor. To keep the frequency constant, the speed of the electric motor turning it was controlled with a feedback loop. In one method, a sample of the output signal is applied to a high-Q
157:(1891, 15 kHz), Salomons and Pyke (1891, 9 kHz), Parsons and Ewing (1892, 14 kHz.), Siemens (5 kHz), B. G. Lamme (1902, 10 kHz), but none was able to reach the frequencies required for radio transmission, above 20 kHz.
1140:
linking two coils. The periphery of the rotor is embraced by a circular iron stator with a C-shaped cross-section, divided into narrow poles, the same number as the rotor has, carrying two sets of coils. One set of coils is energized with
1214:
motor was operated at slips of 4% to 20%, giving speeds of 864 to 720 RPM. Transmitters installed in Europe, operating on 50-cycle power, had a wavelength range of 12,500 to 28,800 meters due to the lower speed of the driving motor.
1187:
is the product of the number of rotor poles and the revolutions per second. Higher radio frequencies thus require more poles, a higher rotational speed, or both. Alexanderson alternators were used to produce radio waves in the
148:
were run at a great enough cycle speed (that is, if it turned fast enough and was built with a large enough number of magnetic poles on its armature) it would generate continuous waves at radio frequency. Starting with
1285:
Because of the limits of the number of poles and rotational speed of a machine, the
Alexanderson alternator is capable of generating transmission frequencies up to around 600 kHz in the lower
1278:'s "Admiralty Handbook of Wireless Telegraphy" cover this in considerable detail, mostly as an explanation as to why the navy did not use that particular technology. However, the US Navy did.
1100:
Marion transmitters were used until 1957. One was scrapped in 1961 and the other was reportedly handed over to the U.S. Bureau of
Standards and stored in a Smithsonian Institution warehouse.
212:
Alexanderson would receive a patent in 1911 for his device. The Alexanderson alternator followed Fessenden's rotary spark-gap transmitter as the second radio transmitter to be
1096:
transmitter at Bolinas, California, again for Pacific ocean communication. Both Haiku alternators were sold for salvage in 1969, possibly to Kreger Company of California.
189:
by shore stations, but was too large and heavy to be installed on most ships. In 1906 the first 50-kilowatt alternators were delivered. One was to Reginald Fessenden at
120:, pulses of radio waves which died out to zero quickly. By the 1890s it was realized that damped waves had disadvantages; their energy was spread over a
289:
268:$ 5,000 in business in exchange for exclusive rights to use the alternator, but just as the deal was about to go through, the American president
304:
Thorn L. Mayes identified the production of ten pairs of 200 KW Alexanderson alternators, totaling 20 transmitters, in the period up to 1924:
202:
1801:
1489:
1120:
Closeup of above rotor. It has 300 narrow slots cut through the rotor. The "teeth" between the slots are the magnetic poles of the machine.
1358:
band), but the advances in technology required to allow a large rotor to be spun at the immensely high speeds necessary without suffering
1261:
The Alexanderson alternator produced "purer" continuous waves than the arc converter, whose nonsinusoidal output generated significant
885:
Delivered 1924, returned to Radio Central Rocky Point in 1926 because more efficient vacuum tube transmitters were now available
1703:
1773:
1836:
915:
Beginning in 1941, seven of the twenty original 200 KW alternators were put into service by the U.S. Navy and Air Force:
181:
for an alternator that generated a frequency of 100,000 hertz for continuous wave radio. The alternator was designed by
1499:
1317:
1690:
Mayes (1989), quoting July 15, 1976 correspondence from "the Commanding Officer of the USCG Station Hawaii", page 180.
1718:
1795:
1246:, so for a given output power they could communicate over longer distances. In addition, continuous waves could be
277:
116:
273:
1651:"200 Kilowatt Alexanderson Transmitters Used in U.S.A. during and after WW II" (table), Mayes (1989), page 183.
1282:
for any answer). There was also the risk that it would allow enemy vessels to detect the presence of the ship.
1145:
and produces a magnetic field in the air gap in the stator, which passes axially (sideways) through the rotor.
1789:
1407:
1243:
121:
293:
1851:
1841:
1741:
1230:
invented in 1903, the Alexanderson alternator was one of the first radio transmitters that generated
344:
239:
radio transmission of the human voice. The last remaining operable Alexanderson alternator is at the
206:
198:
190:
164:
Alexanderson 200-kW motor-alternator set installed at the US Navy's New Brunswick, NJ station, 1920.
131:
with an audio signal to transmit sound. Efforts were made to invent transmitters that would produce
1639:
285:
240:
141:
1382:
243:
in Sweden and was in regular service until 1996. It continues to be operated for a few minutes on
583:
82:
272:
requested that GE decline the offer, which would have given the British (who were the leader in
1312:
1307:
679:
194:
86:
24:
1516:
1455:
1424:
276:) dominance over worldwide radio communications. GE complied with the request and joined with
1334:
1254:
to carry sound. The Alexanderson alternator was one of the first transmitters to be used for
1235:
654:
530:
405:
221:
111:
1813:
1738:
Letter to Mr. Mayes from Lt. Francis J. Kishima Commanding Officer USCG Omega Station Hawaii
1568:
1846:
1359:
1255:
1173:
281:
236:
225:
213:
127:
so transmitters on different frequencies interfered with each other, and they could not be
56:
8:
1820:
1724:
1355:
467:
186:
44:
1607:
1206:
1189:
1169:
182:
174:
40:
1714:
1611:
1495:
107:
1704:"Below 535: A Historical Review of Continuous Wave Radio Frequency Power Generators"
1597:
1302:
1108:
534:
265:
244:
178:
1290:
1231:
1150:
261:
133:
63:
52:
1602:
1585:
1362:
did not occur until long after the Alexanderson alternator had become obsolete.
1142:
1137:
594:
296:(RCA), giving American companies control of American radio for the first time.
269:
124:
1748:
1729:. Philadelphia & New York: J. B. Lippincott (1941), pp. 349–352, 372.
247:, which is either the last Sunday in June or first Sunday in July every year.
1830:
1759:
1542:
1227:
1202:
1133:
1116:
409:
150:
1251:
1184:
154:
78:
19:
1732:
Notes from the Navy Institute proceedings 1952 from M.G. Abernathy files.
1286:
1239:
1157:
256:
232:
217:
74:
59:(AM) signals by radio. It was used from about 1910 in a few "superpower"
48:
1783:
1275:
1247:
1165:
1161:
1129:
471:
348:
160:
145:
128:
103:
67:
36:
1660:
1329:
1262:
1180:
27:, Sweden, the only remaining example of an Alexanderson transmitter.
153:
in 1889, a series of researchers built high frequency alternators,
60:
910:
1807:
839:
Seized by German army 9/1939, who destroyed the stations in 1945
185:. The Alexanderson alternator was extensively used for long-wave
1735:
Letter to M.G. Abernathy from G. Warren Clark Captain USNR (Ret)
1570:
The principles of electric wave telegraphy and telephony, 2nd Ed
1265:, so the alternator was preferred for long-distance telegraphy.
1817:
1160:, whose secondary winding is connected to the antenna circuit.
598:
1491:
The Continuous Wave: Technology and American Radio, 1900-1932
1149:
sinusoidally at a rapid rate. These changes in flux induce a
229:
73:
Although superseded in the early 1920s by the development of
1706:, Antique Wireless Association column edited by Frank Lotito
51:. It was one of the first devices capable of generating the
1156:
The RF collector coils are all interconnected by an output
137:-- a sinusoidal alternating current at a single frequency.
1183:
of the current generated by an Alexanderson alternator in
228:, the Alexanderson alternator was an important high-power
77:, the Alexanderson alternator continued to be used until
43:
beginning in 1904, for the generation of high-frequency
1624:"200 KW Alexanderson Alternator Transmitters" (table),
372:
Replaced a 50 KW alternator installed in February 1917
250:
1274:
available at the time. In fact, early editions of the
1223:
higher rotor speeds were required, up to 20,000 RPM.
66:
stations to transmit transoceanic message traffic by
23:
200 kW Alexanderson alternator preserved at the
1293:
and higher frequencies being physically impossible.
1742:Milestones:Yosami Radio Transmitting Station, 1929
1435:(154). Electrical Engineer Co.: 437 April 15, 1891
16:High-frequency AC generator for radio transmission
1640:"The Alexanderson 200-kW Alternator Transmitters"
216:to carry the human voice. Until the invention of
106:were discovered in 1887, the first generation of
1828:
1796:"Kahuku Marconi Wireless Station, O'ahu, Hawaii"
1573:. London: Longmans, Green and Co. pp. 5–10.
1383:"Milestones:Alexanderson Radio Alternator, 1904"
1153:voltage in a second set of coils on the stator.
911:U.S. military use during and after World War II
290:Westinghouse Electric and Manufacturing Company
1790:Alexanderson Alternators at Haiku Valley, Oahu
1726:Men and Volts, the Story of General Electric
1521:Annual Report of the Smithsonian Institution
1168:of the radio frequency energy was done by a
1626:Wireless Communication in the United States
1425:"Prof. Thomson's new alternating generator"
495:Replaced a Marconi timed spark transmitter
433:Replaced a Marconi timed spark transmitter
1713:Counterpoint, Washington D.C. USA, (1996)
1642:. "Ports O' Call" Vol 4. 1975. Appendix D.
1447:
1417:
1601:
1562:
1560:
1558:
1556:
1514:
1217:
1709:David E. Fisher and Marshall J. Fisher,
1535:
1508:
1483:
1481:
1115:
1107:
786:Initially 18.600 m, parallel connection
159:
70:to similar stations all over the world.
18:
1804:(picture gallery) by David Jessup, 2012
1774:"The World's Greatest Wireless Station"
1583:
1566:
1453:
1829:
1784:"American Marconi Station, Marion, MA"
1553:
1548:Alternating Electric Current Generator
1487:
1816:Alexanderson alternator preserved at
1494:. Princeton Univ. Press. p. 53.
1478:
1454:Thomson, Elihu (September 12, 1890).
1414:(London), January 22, 1892, page 302.
582:To Marion, Massachusetts 1949. Later
97:
1195:
251:World War I and the formation of RCA
144:pointed out that, if an electrical
13:
1780:by Charles Taussig, pages 312-327.
1696:
1590:The Annals of the American Academy
14:
1863:
1767:
1711:Tube, the Invention of Television
1523:. Government Printing Office: 172
1128:The machine operates by variable
1814:"The Radio Station SAQ Grimeton"
1268:
278:American Telephone and Telegraph
25:Grimeton radiotelegraphy station
1684:
1675:
1666:
1654:
1645:
1632:
1618:
1347:
812:Preserved at Grimeton, Sweden.
274:submarine communications cables
168:
1808:"Tuckerton Wireless 1912-1955"
1586:"The Commercial Uses of Radio"
1577:
1567:Fleming, John Ambrose (1910).
1408:"Radiation of Electric Energy"
1401:
1375:
1:
1661:"The Alexanderson Alternator"
1369:
1798:by Jonathan H, June 20, 2007
1672:Mayes (1989), pages 176-177.
1060:Tuckerton, New Jersey (WGG)
1042:Tuckerton, New Jersey (WCI)
1001:Marion, Massachusetts (WQR)
960:Marion, Massachusetts (WSO)
294:Radio Corporation of America
7:
1837:History of radio technology
1603:10.1177/0002716229142001S09
1387:IEEE Global History Network
1325:radio frequency alternators
1296:
1234:. In contrast, the earlier
868:Pernambuco, Recife, Brazil
299:
55:needed for transmission of
10:
1868:
1802:"Marion Mass. Alternators"
1488:Aitken, Hugh G.J. (2014).
1172:, which was also used for
1112:Rotor of 200 kW alternator
1081:Bolinas, California (KET)
979:Bolinas, California (KET)
92:
1753:High Frequency Alternator
1515:Fessenden, R. A. (1908).
1176:and voice transmissions.
1103:
1036:
995:
954:
884:
867:
838:
819:
764:
713:
653:
593:
528:
521:To Haiku, Hawaii in 1942
466:
459:To Haiku, Hawaii in 1942
404:
343:
207:New Brunswick, New Jersey
199:Gloucester, Massachusetts
191:Brant Rock, Massachusetts
1723:Hammond, John Winthrop.
1663:by Jerry Proc (jproc.ca)
1340:
1132:(similar to an electric
286:Western Electric Company
241:VLF transmitter Grimeton
203:American Marconi Company
142:Frederick Thomas Trouton
85:as a key achievement in
75:vacuum-tube transmitters
1746:E. F. W. Alexanderson,
1681:Mayes (1989), page 176.
1429:The Electrical Engineer
584:Smithsonian Institution
83:list of IEEE Milestones
33:Alexanderson alternator
1584:Harbord, J.G. (1929).
1410:by Frederick Trouton,
1313:Goldschmidt alternator
1308:Grimeton Radio Station
1238:generated a string of
1236:spark-gap transmitters
1218:Performance advantages
1121:
1113:
1037:Tuckerton, New Jersey
996:Marion, Massachusetts
714:Caernarvon, Wales, UK
680:Goldschmidt alternator
195:John Hays Hammond, Jr.
165:
114:, produced strings of
112:spark gap transmitters
87:electrical engineering
53:continuous radio waves
28:
1749:U.S. patent 1,008,577
1335:Resolver (electrical)
1119:
1111:
163:
22:
1517:"Wireless Telephony"
1360:catastrophic failure
1174:amplitude modulation
1076:Bolinas, California
1021:Radio Central (WSS)
282:United Fruit Company
237:amplitude modulation
226:Armstrong oscillator
224:in 1913 such as the
187:radio communications
140:In an 1891 lecture,
1823:in Grimeton, Sweden
1821:World Heritage Site
1760:U.S. patent 447,921
1543:U.S. patent 447,921
201:and another to the
57:amplitude modulated
45:alternating current
1852:Swedish inventions
1550:" (March 10, 1891)
1207:resonant frequency
1190:very low frequency
1170:magnetic amplifier
1122:
1114:
183:Ernst Alexanderson
175:Reginald Fessenden
166:
108:radio transmitters
98:Prior developments
41:Ernst Alexanderson
29:
1842:Radio electronics
1778:The Book of Radio
1776:(Radio Central),
1466:. London: 529–530
1196:Frequency control
1093:
1092:
908:
907:
657:, New Jersey, US
49:radio transmitter
1859:
1762:
1751:
1691:
1688:
1682:
1679:
1673:
1670:
1664:
1658:
1652:
1649:
1643:
1638:Thorn L. Mayes.
1636:
1630:
1622:
1616:
1615:
1605:
1581:
1575:
1574:
1564:
1551:
1546:, Nikola Tesla "
1545:
1539:
1533:
1532:
1530:
1528:
1512:
1506:
1505:
1485:
1476:
1475:
1473:
1471:
1451:
1445:
1444:
1442:
1440:
1421:
1415:
1405:
1399:
1398:
1396:
1394:
1379:
1363:
1351:
1303:Alexanderson Day
1232:continuous waves
1166:telegraph keying
1136:), changing the
918:
917:
765:Varberg, Sweden
324:Frequency (kHz)
307:
306:
280:(AT&T), the
266:General Electric
255:The outbreak of
245:Alexanderson Day
179:General Electric
177:contracted with
134:continuous waves
37:rotating machine
1867:
1866:
1862:
1861:
1860:
1858:
1857:
1856:
1827:
1826:
1792:by David Jessup
1770:
1765:
1758:
1747:
1699:
1697:Further reading
1694:
1689:
1685:
1680:
1676:
1671:
1667:
1659:
1655:
1650:
1646:
1637:
1633:
1623:
1619:
1582:
1578:
1565:
1554:
1541:
1540:
1536:
1526:
1524:
1513:
1509:
1502:
1486:
1479:
1469:
1467:
1460:The Electrician
1452:
1448:
1438:
1436:
1423:
1422:
1418:
1412:The Electrician
1406:
1402:
1392:
1390:
1381:
1380:
1376:
1372:
1367:
1366:
1352:
1348:
1343:
1323:Bethenod-Latour
1299:
1271:
1226:Along with the
1220:
1198:
1151:radio-frequency
1106:
943:
938:
933:
928:
913:
820:Warsaw, Poland
529:Radio Central,
321:Wavelength (m)
317:
302:
262:British Marconi
253:
171:
100:
95:
81:. It is on the
64:radiotelegraphy
39:, developed by
17:
12:
11:
5:
1865:
1855:
1854:
1849:
1844:
1839:
1825:
1824:
1811:
1805:
1799:
1793:
1787:
1786:by Henry Brown
1781:
1769:
1768:External links
1766:
1764:
1763:
1755:
1744:
1739:
1736:
1733:
1730:
1721:
1707:
1700:
1698:
1695:
1693:
1692:
1683:
1674:
1665:
1653:
1644:
1631:
1617:
1576:
1552:
1534:
1507:
1501:978-1400854608
1500:
1477:
1446:
1416:
1400:
1373:
1371:
1368:
1365:
1364:
1345:
1344:
1342:
1339:
1338:
1337:
1332:
1327:
1315:
1310:
1305:
1298:
1295:
1270:
1267:
1258:transmission.
1244:frequency band
1219:
1216:
1197:
1194:
1143:direct current
1105:
1102:
1091:
1090:
1087:
1085:
1082:
1079:
1077:
1074:
1070:
1069:
1066:
1064:
1061:
1058:
1056:
1052:
1051:
1048:
1046:
1043:
1040:
1038:
1035:
1031:
1030:
1027:
1024:
1022:
1019:
1016:
1012:
1011:
1008:
1005:
1002:
999:
997:
994:
990:
989:
986:
983:
980:
977:
975:
971:
970:
967:
964:
961:
958:
956:
955:Haiku, Hawaii
953:
949:
948:
945:
940:
935:
930:
925:
922:
912:
909:
906:
905:
902:
900:
897:
895:
893:
891:
887:
886:
883:
880:
878:
875:
873:
871:
869:
866:
862:
861:
859:
857:
854:
851:
848:
845:
841:
840:
837:
835:
833:
830:
827:
824:
821:
818:
814:
813:
810:
807:
804:
801:
798:
795:
792:
788:
787:
784:
781:
778:
775:
772:
769:
766:
763:
759:
758:
756:
753:
751:
748:
745:
742:
739:
735:
734:
732:
729:
727:
724:
721:
718:
715:
712:
708:
707:
705:
702:
699:
696:
693:
690:
687:
683:
682:
676:
673:
670:
667:
664:
661:
658:
652:
648:
647:
645:
642:
639:
636:
633:
630:
627:
623:
622:
620:
617:
614:
611:
608:
605:
602:
592:
588:
587:
580:
578:
575:
572:
569:
566:
563:
559:
558:
556:
553:
550:
547:
544:
541:
538:
527:
523:
522:
519:
516:
513:
510:
507:
504:
501:
497:
496:
493:
490:
487:
484:
481:
478:
475:
465:
461:
460:
457:
454:
451:
448:
445:
442:
439:
435:
434:
431:
428:
425:
422:
419:
416:
413:
403:
399:
398:
396:
393:
390:
387:
384:
381:
378:
374:
373:
370:
367:
364:
361:
358:
355:
352:
342:
338:
337:
334:
331:
328:
325:
322:
319:
314:
311:
301:
298:
270:Woodrow Wilson
252:
249:
235:, and allowed
170:
167:
125:frequency band
99:
96:
94:
91:
15:
9:
6:
4:
3:
2:
1864:
1853:
1850:
1848:
1845:
1843:
1840:
1838:
1835:
1834:
1832:
1822:
1819:
1815:
1812:
1809:
1806:
1803:
1800:
1797:
1794:
1791:
1788:
1785:
1782:
1779:
1775:
1772:
1771:
1761:
1756:
1754:
1750:
1745:
1743:
1740:
1737:
1734:
1731:
1728:
1727:
1722:
1720:
1719:1-887178-17-1
1716:
1712:
1708:
1705:
1702:
1701:
1687:
1678:
1669:
1662:
1657:
1648:
1641:
1635:
1629:calculations.
1627:
1621:
1613:
1609:
1604:
1599:
1595:
1591:
1587:
1580:
1572:
1571:
1563:
1561:
1559:
1557:
1549:
1544:
1538:
1522:
1518:
1511:
1503:
1497:
1493:
1492:
1484:
1482:
1465:
1461:
1457:
1450:
1434:
1430:
1426:
1420:
1413:
1409:
1404:
1388:
1384:
1378:
1374:
1361:
1357:
1350:
1346:
1336:
1333:
1331:
1328:
1326:
1324:
1320:
1316:
1314:
1311:
1309:
1306:
1304:
1301:
1300:
1294:
1292:
1288:
1283:
1279:
1277:
1269:Disadvantages
1266:
1264:
1259:
1257:
1253:
1249:
1245:
1241:
1237:
1233:
1229:
1228:arc converter
1224:
1215:
1211:
1208:
1204:
1203:tuned circuit
1193:
1191:
1186:
1182:
1177:
1175:
1171:
1167:
1163:
1159:
1154:
1152:
1146:
1144:
1139:
1138:magnetic flux
1135:
1134:guitar pickup
1131:
1126:
1118:
1110:
1101:
1097:
1088:
1086:
1083:
1080:
1078:
1075:
1072:
1071:
1067:
1065:
1062:
1059:
1057:
1054:
1053:
1049:
1047:
1044:
1041:
1039:
1033:
1032:
1028:
1025:
1023:
1020:
1017:
1014:
1013:
1009:
1006:
1003:
1000:
998:
992:
991:
987:
984:
981:
978:
976:
973:
972:
968:
965:
962:
959:
957:
951:
950:
946:
941:
936:
931:
926:
923:
920:
919:
916:
903:
901:
898:
896:
894:
892:
889:
888:
881:
879:
876:
874:
872:
870:
864:
863:
860:
858:
855:
852:
849:
846:
843:
842:
836:
834:
831:
828:
825:
822:
816:
815:
811:
808:
805:
802:
799:
796:
793:
790:
789:
785:
782:
779:
776:
773:
770:
767:
761:
760:
757:
754:
752:
749:
746:
743:
740:
737:
736:
733:
730:
728:
725:
722:
719:
716:
710:
709:
706:
703:
700:
697:
694:
691:
688:
685:
684:
681:
677:
674:
671:
668:
665:
662:
659:
656:
650:
649:
646:
643:
640:
637:
634:
631:
628:
625:
624:
621:
618:
615:
612:
609:
606:
603:
600:
596:
590:
589:
585:
581:
579:
576:
573:
570:
567:
564:
561:
560:
557:
554:
551:
548:
545:
542:
539:
536:
532:
525:
524:
520:
517:
514:
511:
508:
505:
502:
499:
498:
494:
491:
488:
485:
482:
479:
476:
473:
469:
463:
462:
458:
455:
452:
449:
446:
443:
440:
437:
436:
432:
429:
426:
423:
420:
417:
414:
411:
410:Massachusetts
407:
401:
400:
397:
394:
391:
388:
385:
382:
379:
376:
375:
371:
368:
365:
362:
359:
356:
353:
350:
346:
345:New Brunswick
340:
339:
335:
332:
329:
326:
323:
320:
315:
312:
309:
308:
305:
297:
295:
291:
287:
283:
279:
275:
271:
267:
263:
258:
248:
246:
242:
238:
234:
231:
227:
223:
219:
215:
210:
208:
204:
200:
196:
193:, another to
192:
188:
184:
180:
176:
162:
158:
156:
152:
151:Elihu Thomson
147:
143:
138:
136:
135:
130:
126:
123:
119:
118:
113:
109:
105:
90:
88:
84:
80:
76:
71:
69:
65:
62:
58:
54:
50:
47:for use as a
46:
42:
38:
34:
26:
21:
1777:
1752:
1725:
1710:
1686:
1677:
1668:
1656:
1647:
1634:
1625:
1620:
1593:
1589:
1579:
1569:
1547:
1537:
1525:. Retrieved
1520:
1510:
1490:
1468:. Retrieved
1463:
1459:
1449:
1437:. Retrieved
1432:
1428:
1419:
1411:
1403:
1391:. Retrieved
1386:
1377:
1349:
1322:
1318:
1284:
1280:
1272:
1260:
1252:audio signal
1240:damped waves
1225:
1221:
1212:
1199:
1178:
1155:
1147:
1127:
1123:
1098:
1094:
1029:Smithsonian
914:
809:Operational
303:
292:to form the
254:
211:
172:
169:Construction
155:Nikola Tesla
139:
132:
117:damped waves
115:
101:
79:World War II
72:
32:
30:
1847:Alternators
1289:band, with
1287:Medium wave
1158:transformer
678:Replaced a
531:Rocky Point
257:World War I
233:transmitter
222:oscillators
218:vacuum-tube
104:radio waves
1831:Categories
1757:N. Tesla,
1370:References
1276:Royal Navy
1162:Modulation
1130:reluctance
1084:1942-1946
1063:1942-1948
1045:1942-1948
1026:1949-1957
1007:1949-1957
1004:1941-1948
985:1947-1957
982:1942-1946
966:1947-1957
963:1942-1946
944:Operation
939:Operation
472:California
349:New Jersey
327:Installed
146:alternator
68:Morse code
1810:(gallery)
1612:144710174
1596:: 57–63.
1527:April 18,
1470:April 18,
1439:April 18,
1330:Tonewheel
1319:Joly-Arco
1291:shortwave
1263:harmonics
1248:modulated
1181:frequency
947:Scrapped
942:Air Force
934:Location
924:Location
655:Tuckerton
333:Scrapped
313:Location
214:modulated
173:In 1904,
129:modulated
1456:"letter"
1297:See also
1250:with an
1205:, whose
932:Original
832:12/1923
549:11/1921
535:New York
486:10/1920
336:Remarks
300:Stations
288:and the
264:offered
220:(valve)
61:longwave
1393:29 July
850:18,293
826:21,127
797:17,442
771:17,442
726:4/1921
720:14,111
692:13,575
669:3/1921
663:16,304
632:16,667
607:16,120
568:15,957
543:16,484
506:15,600
480:13,100
468:Bolinas
450:7/1922
444:11,628
424:4/1920
418:13,423
389:2/1920
383:13,274
363:6/1918
357:13,761
93:History
1818:UNESCO
1717:
1610:
1498:
1389:. IEEE
1104:Design
899:never
877:never
744:9,592
599:Hawaii
595:Kahuku
406:Marion
330:Idled
284:, the
110:, the
102:After
1608:S2CID
1341:Notes
1185:hertz
1089:1946
1068:1955
1050:1955
1018:AFA2
1010:1961
988:1969
969:1969
929:Sign
904:1927
882:1927
856:1923
853:16.4
829:14.2
806:1946
803:1924
800:17.2
783:1960
780:1946
777:1924
774:17.2
755:1939
750:1921
747:31.3
731:1939
723:21.2
704:1955
701:1948
698:1922
695:22.1
675:1955
672:1948
666:18.4
644:1938
641:1930
638:1921
635:18.0
619:1938
616:1930
613:1920
610:18.6
601:, US
577:1948
574:1921
571:18.8
555:1951
552:1948
546:18.2
537:, US
518:1969
515:1930
512:1921
509:19.2
492:1946
489:1930
483:22.9
474:, US
456:1969
453:1932
447:25.8
430:1961
427:1932
421:22.3
412:, US
395:1953
392:1948
386:22.6
369:1953
366:1948
360:21.8
351:, US
318:sign
230:radio
122:broad
35:is a
1715:ISBN
1529:2015
1496:ISBN
1472:2015
1441:2015
1395:2011
1321:and
1179:The
937:Navy
927:Call
921:No.
847:AXL
823:AXO
794:SAQ
768:SAQ
741:GLC
717:MUU
689:WGG
660:WCI
629:KIE
604:KGI
565:WSS
540:WQK
503:KET
477:KET
441:WSO
415:WQR
380:WRT
354:WII
316:Call
310:No.
1598:doi
1594:142
1356:VHF
1164:or
890:20
865:19
844:18
817:17
791:16
762:15
738:14
711:13
686:12
651:11
626:10
205:in
197:in
31:An
1833::
1606:.
1592:.
1588:.
1555:^
1519:.
1480:^
1464:25
1462:.
1458:.
1433:11
1431:.
1427:.
1385:.
1256:AM
1073:7
1055:6
1034:5
1015:4
993:3
974:2
952:1
597:,
591:9
586:.
562:8
533:,
526:7
500:6
470:,
464:5
438:4
408:,
402:3
377:2
347:,
341:1
209:.
89:.
1614:.
1600::
1531:.
1504:.
1474:.
1443:.
1397:.
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
