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AES Section Meeting Reports

Chicago - November 17, 2010

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Summary

The November 2010 meeting of the Chicago AES Section was held at Shure Incorporated, located in Niles, Illinois. This was a special joint meeting between the Chicago AES Section and the IEEE EMC Society which resulted in a combined attendance of over 80 members and non-members. The speakers for the evening were four development engineers from Shure Incorporated who have focused on improving the RF immunity of audio products.

The presentation started with acknowledging the challenge that audio developers have with the proliferation of wireless devices in our lives. Ambient RF from broadcast sources, personal communications devices, data signals, and a host of others all have a direct effect on audio products. The "yakkitta-yakkitta-buzz-buzz" of interfering RF signals being demodulated in an audio product was demonstrated by holding a GSM enabled phone within a few inches from an "unprotected" device. Then the phone was held close to a "protected" or immune device and the audience cheered when no audible interference was detected.

The presenters related their experiences in addressing interference and signal disruption and offered various design considerations and test methods. They reviewed several lessons that they learned as key takeaways such as "copper tape is your friend...consider it RF duct tape", avoid ¼ wavelength product dimensions, and proper shielding and wiring practices are critical — double serve shield with foil was found to provide the highest level of immunity.

Many great questions from the audience were posed ranging from options of simulating the interference in an anechoic chamber, the level of involvement the FCC has provided in terms of testing the GSM affect on devices, investigating the full RF spectrum that created the GSM interference, and various shielding considerations such as using conduit for cable runs to questions regarding the product/project design and cost limitations when considering dimensional changes to address immunity.

The Chicago AES Section would like to extend a special thanks to Scott Brumm, Roger Grinnip, Mike Moffit, and Marty Reiling for a wonderful presentation and interactive discussion.

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AES - Audio Engineering Society