The National Association of Broadcasters (NAB) has asked the U.S. Federal Communications Commission to conduct investigations into the operations of each Sirius Satellite Radio and XM Satellite Radio, the NAB announced.

In separate Oct. 23 letters to the FCC, the NAB called for the FCC to investigate the satellite radio companies’ use of terrestrial repeater networks, and for a review of the regulatory status.

The NAB accuses XM and Sirius of operating terrestrial repeaters, used by the companies to boost their signals around metropolitan areas where satellite signals may be blocked by buildings and other obstructions, “that were constructed and deployed inconsistently with FCC rules.”

According to the letter signed by NAB President and CEO David Rehr, “these latest disclosures reveal a persistent corporate (if not industry) circumvention of the FCC’s regulations.”

Separately, NAB is calling for the FCC to investigate the “privileged regulatory position” used by satellite radio. The NAB claims that the satellite radio companies use their status as subscription services to avoid regulatory rules applied to free-radio broadcasts. The NAB claims that recent moves by satellite radio to offer free trials of their services, such as an XM deal with Acura and the availability of Howard Stern’s Sirius show on the Internet, mean that “drawing a regulatory distinction between satellite and traditional broadcast radio simply because satellite radio content is available on a subscription basis may no longer be justified.”