EMC Testing Services

RF "ambient free" anechoic chambers

Anechoic chambers represent state-of-the-art technology for international electromagnetic compatibility (EMC). "Ambients" refers to the radio frequency signals present during testing that are not from the product being tested. Ambients include television, radio, cellular phones, pagers, police radios, etc.

When selecting a test site, manufacturers should consider the following:

• All open area test sites, even those in rural areas, must deal with ambient signals.
• Measuring the radio frequency emissions of a product buried in these "ambients" is very difficult and can take a long time to complete correctly.

Enclosed and shielded, UL's metal chambers are lined with ferrite and radio frequency (RF) absorbers. UL currently has 3- or 10-meter anechoic chambers in all of UL's test facilities in the US.

UL's anechoic chambers provide the following benefits to manufacturers:

• UL can complete fully compliant and accurate emissions scans faster than is possible on an open area test site.
• Ambient free environment with emissions performance very close to the ideal or "perfect" emissions curve, as specified in the American National Standards Institute (ANSI) C63.4 for highly accurate measurements.
• Four-meter turntables that can handle products weighing up to 14,000 pounds.
• Large (8' x 10') doors for convenient installation and large-product set-ups.
• Special access bulkheads for convenient wiring of auxiliary equipment or loads.
• These chambers are also qualified for radiated immunity testing with a 3-meter wide uniform field.

UL's anechoic chambers can reduce test time over the typical method of conducting preliminary measurements and Open Area Test Sites (OATS) by 75 percent.

Additional Resources

• Field uniformity
• Site attenuation