indoor noise conditions in the fm broadcast band steve johnston director of engineering and...
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Indoor Noise Conditions in the FM Broadcast Band
Steve JohnstonDirector of Engineering and Operations
Wisconsin Public Radio
NAB Engineering Conference 2010
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Introduction
Radio hobbyists – Ham radio operators,
shortwave listeners, broadcast DXers, and other enthusiasts are usually quite aware of the growing radio noise issues we face…
But most people are unaware of this “noise pollution” problem.
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Observations
How many of us have received complaints from listeners, staff, or management regarding reception problems?
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Observations A significant number of Wisconsin
Public Radio analog listeners report deteriorating reception:
In the past five years, WPR Audience Services “Listener Logs” show a 37% increase in email and telephone complaints related to reception.
“I used to get good reception, but not anymore…”
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Observations
FM HD Radio indoor reception is simply not as good as predicted – both at WPR and industry-wide.
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Hypothesis
Growing levels of indoor noise may be masking fringe-area analog signalsCould be bothering reception of digital HD Radio and HDTV as well. High indoor noise levels might be contributing to the unexpected HD Radio “building penetration” issues.
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MeasurementsPortable spectrum analyzer with home-made loop antenna.
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MeasurementsBalun-fed loop antenna 1/4–wavelength in circumference
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Field Tests
Not absolute measurements – instead a comparison of outdoor to indoor reception conditions
Study locationsSuburban housesUrban apartmentsUrban offices
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Field Tests
Suburban homes
Fitchburg, Wisconsin
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Outside Suburban Home
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Inside Suburban Home
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Field Tests
Urban Apartments
Quisling Apartments - Madison, Wisconsin.
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Outside Apartment Building
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Inside Apartment
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Field Tests
Urban Offices
UW Vilas Hall - Madison, Wisconsin
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Outside Office Building
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Inside Office Building
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Typical Noise Sources
Typical Noise Sources
Switching power suppliesConsumer electronicsOffice equipment
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Examples of Noise Sources RCA (Thomson) model DRC200N DVD/CD player
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Examples of Noise Sources
Jishisheng Wanji Electric Appliance Model SP80
Battery charger for electric scooter
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Examples of Noise SourcesVoltek (Volgen) model EXU-15010
Office equipment power supply
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Examples of Noise SourcesViewsonic Model LSE9901B1250 Power supply for monitor
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Examples of Noise SourcesMotorola model DCH4-050MV-0301 Cellphone charger
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Examples of Noise SourcesNo-Name (IV) (F WHK) type FW7600/05 Cellphone charger
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Examples of Noise SourcesDelta Electronics model ADP-15FB PDA charger
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Examples of Noise SourcesLite-On Technology model PA-1650-01 Toshiba notebook PC
power supply (Toshiba p/n PA3396U-1ACA)
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Examples of Noise SourcesBroksonic Corporation model CTGV-5463TCT Television set
“Broke-sonic” - a perfect name for this noisy product!
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Conclusion
Summary of results
Increase in noise from outdoor to indoor was dramatic in all cases.
In some indoor locations a 20 to 30 dB increase
in overall noise.
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ConclusionWhy is this happening?
Devices are being made without adequate concern for their incidental RF radiation.
Anecdotal reports: prototypes are RFI tested, but actual products are built cheaper and not to tested specs.Switching power supplies from third-parties that have not been tested.
Regulatory agencies may have lost control of the situation.
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Questions?
Observations?
Thank you… Steve Johnston
Director of Engineering and Operations
Wisconsin Public Radio