Indoor Noise Conditions in the FM Broadcast Band

Steve JohnstonDirector of Engineering and Operations

Wisconsin Public Radio

NAB Engineering Conference 2010

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.

Observations

How many of us have received complaints from listeners, staff, or management regarding reception problems?

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…”

Observations

FM HD Radio indoor reception is simply not as good as predicted – both at WPR and industry-wide.

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.

MeasurementsPortable spectrum analyzer with home-made loop antenna.

MeasurementsBalun-fed loop antenna 1/4–wavelength in circumference

Field Tests

Not absolute measurements – instead a comparison of outdoor to indoor reception conditions

Study locationsSuburban housesUrban apartmentsUrban offices

Field Tests

Suburban homes

Fitchburg, Wisconsin

Outside Suburban Home

Inside Suburban Home

Field Tests

Urban Apartments

Quisling Apartments - Madison, Wisconsin.

Outside Apartment Building

Inside Apartment

Field Tests

Urban Offices

UW Vilas Hall - Madison, Wisconsin

Outside Office Building

Inside Office Building

Typical Noise Sources

Typical Noise Sources

Switching power suppliesConsumer electronicsOffice equipment

Examples of Noise Sources RCA (Thomson) model DRC200N DVD/CD player

Examples of Noise Sources

Jishisheng Wanji Electric Appliance Model SP80

Battery charger for electric scooter

Examples of Noise SourcesVoltek (Volgen) model EXU-15010

Office equipment power supply

Examples of Noise SourcesViewsonic Model LSE9901B1250 Power supply for monitor

Examples of Noise SourcesMotorola model DCH4-050MV-0301 Cellphone charger

Examples of Noise SourcesNo-Name (IV) (F WHK) type FW7600/05 Cellphone charger

Examples of Noise SourcesDelta Electronics model ADP-15FB PDA charger

Examples of Noise SourcesLite-On Technology model PA-1650-01 Toshiba notebook PC

power supply (Toshiba p/n PA3396U-1ACA)

Examples of Noise SourcesBroksonic Corporation model CTGV-5463TCT Television set

“Broke-sonic” - a perfect name for this noisy product!

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.

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.

Questions?

Observations?

Thank you… Steve Johnston

Director of Engineering and Operations

Wisconsin Public Radio