Download - Radio interference
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Radio Interference
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OverviewWhat is it?Radio InterferencePreventing
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What is it?Unwanted signals
◦Effect electronic circuits
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Radio InterferenceInternational Electrotechnical
Commission◦1933 set up International Special
Committee on Radio InterferenceEU
◦EMC Directive (89/336/EC) Immunity Emissions
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Radio Interference TypesNarrow band
◦TX equipmentBroad band
◦Power lines◦Motors◦Computers and TV
Antenna◦Outside of antenna cable◦Unbalanced
Power supplies
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Radio Interference SourcesTransmitting equipment
◦Harmonics◦Wrong frequency
Faulty electronic equipmentSunAurorasSplatter
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RX interference sourcesClipping
◦Square wave Harmonics
Clipping from◦Power◦Microphone
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PreventingFilterDon’t over drive the systemUse balunsRF chokeFaraday CageCablesElectric Earth
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PreventingBaluns
◦Matching between balanced and unbalanced lines
◦Conver between 300/450 W lines and 75 W coax
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PreventingBaluns
◦Wound around a iron core
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PreventingRF choke
◦inductor
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PreventingFaraday Cage
◦Metal cage or mesh◦Can block radio waves
Small gapes depending on wavelength
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PreventingCables
◦Twisted pair Cancelling out
◦Coax Inner conductor Outer “shielding” conductor
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PreventingElectrical earth