Response from: Ron

Ethically, I see no problem with protecting the air space around you. However, the Feds have a different attitude. It is "against the law" to block cell-phone airwaves, even in the privacy of your own home. However, this assumes the Feds can figure out it was you jamming the signal and they can catch you doing it.

Response from: visitor

Jamming devices are illegal in the U.S. **************
Blocking & Jamming The operation of transmitters designed to jam or block wireless communications is a violation of the Communications Act of 1934, as amended ("Act"). See 47 U.S.C. Sections 301, 302a, 333. The Act prohibits any person from willfully or maliciously interfering with the radio communications of any station licensed or authorized under the Act or operated by the U.S. government. 47 U.S.C. Section 333. The manufacture, importation, sale or offer for sale, including advertising, of devices designed to block or jam wireless transmissions is prohibited. 47 U.S.C. Section 302a(b). Parties in violation of these provisions may be subject to the penalties set out in 47 U.S.C. Sections 501-510. Fines for a first offense can range as high as $11,000 for each violation or imprisonment for up to one year, and the device used may also be seized and forfeited to the U.S. government.
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http://wireless.fcc.gov/services/index.htm?job=operations_2&id=cellula
r