After placing the largest deposit among the 168 qualified bidders and leading after the early rounds, DirecTV Group Inc. and Echostar Communications Corp. have dropped out of an auction of wireless spectrum being conducted by the U.S. Federal Communication Commission (FCC).

The companies, which combined their efforts under the joint venture Wireless DBS LLC, failed to submit a bid for the 18^th round of the auction Aug. 16, according to data on the FCC web site. Wireless DBS was the leading bidder after five rounds of the auction.

The auction has raised $9.5 billion after 18 rounds and will continue until there are no new bids or other activity.