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+---- Thread: Passiv radioantenn (/showthread.php?tid=561)
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RE: Passiv radioantenn - Sokrates - 2018-10-21
Skillnaden mellan AM och FM:
Frequency modulation or FM is a form of modulation which conveys information by varying the frequency of a carrier wave; the older amplitude modulation or AM varies the amplitude of the carrier, with its frequency remaining constant.
Mottagning och avstånd:
VHF Radio waves do not travel far beyond the visual horizon, so reception distances for FM stations are usually limited to 30—40 miles (50—65 km) They can also be blocked by hills or buildings.
... AM radio waves, which because of their lower frequency can travel as ground waves or reflect off the ionosphere, so AM radio stations can be received at hundreds (sometimes thousands) of miles. This is a property of the carrier wave's typical frequency (and power), not its mode of modulation.
The range of FM transmission is related to the transmitter's RF power, the antenna gain, and antenna height. Interference from other stations is also a factor in some places.
(en.wikipedia.org/wiki/FM_broadcasting)
RE: Passiv radioantenn - Sokrates - 2018-10-21
FM-bandets polarisationen i Europa kan var vertikal-, horisontell- eller blandad polarisation. Horisontellpolarisation är vanligtvis använd i bergsområden med kuperad terräng.
(tech.ebu.ch/docs/techreview/trev_254-gregorac.pdf)
Vertical polarization is used in AM and FM radio,and horizontal polarization in television.
(books.google.es/books - Webster's New World Telecom Dictionary)
Mer om polarisation:
fmbroadcastantenna.com/polarizationinfo
broadcastengineering.info - Vertical or Circular polarization FM Broadcast
tx.mb21.co.uk/features/recognition/vhf-fm