As debate continues over a possible merger between Sirius and XM satellite radio, XM has filed comments with the Federal Communications Commission backing Sirius's proposed rules for satellite repeaters and wireless transmitters.

Final regulations governing these two technologies "should take into account the well-established hazard that terrestrially-based services can pose to adjacent band satellite services," two attorneys for XM Radio Inc. wrote to the FCC on January 5th in support of Sirius' proposals.

XM filed the statement to back a Sirius petition submitted on October 17th, 2006 that outlines broadcasting rules for satellite Digital Audio Radio Service (DARS or SDARS) repeaters and Wireless Communications Service (WCS) transmitters.

Both XM and Sirius use DARS repeaters to reach customers whose receivers cannot receive a direct satellite signal. But WCS broadcasts, used to pinpoint the location of cell phone users, can sometimes interfere with satellite repeaters.

Sirius proposes that

• Emission limits be established for DARS repeaters and WCS transmitters. Sirius contends that the firm's research indicates that interference from WCS transmitters higher than -44 dBM (milliwatt decibels) will block service to satellite radio subscribers.
• DARS and WCS licensees must give advance notice of their equipment rollouts. "Such notice will ensure all licensees have ample opportunity to investigate whether their operations will be affected by the new deployment and request adjustments, in advance, to avoid interference," Sirius writes.
• Firms be permitted to establish perimeters of an agreed upon size where extra transmitters can be deployed to compensate for interference.

XM's January 5th filing strongly endorses Sirius's proposals.

"Sirius and XM paid more than $170 million for their combined 25 MHz of SDARS spectrum," the firm's attorneys write, "prices paid with knowledge of FCC decisions to restrict WCS license holders from impacting our effective use of spectrum for mobile listeners"—in other words, listeners in cars with satellite receivers.

The filing urges the FCC to issue a public notice asking for comment on Sirius's petition.

The move comes as FCC Chair Kevin Martin is discouraging hopes for a possible merger between XM and Sirius any time soon.

At a press conference today Martin said that such a union would run afoul of 1997 rules that gave the go-ahead for the two services, regulations that prohibit "one entity owning both of these businesses," in Martin's own words.

But these coordinated filings suggest that XM and Sirius may work more closely together even if they cannot combine.