* Order will improve service of rural, regional wireless providers
* Airwaves in 700 MHz band highly valued for powerful signal
* Dish helped broker deal as part of mobile broadband strategy
* Companies position themselves ahead of FCC's spectrum auctions
WASHINGTON, Oct 28 (Reuters) - U.S. telecommunications regulators on Monday formally adopted an agreement by AT&T Inc , Dish Network Corp and other wireless companies to give smaller operators access to devices now made only for AT&T's airwaves.
The Federal Communications Commission's order, approved without a public vote, makes official and elaborates upon a multi-pronged deal brokered by agency staff and wireless companies last month.
Participants made concessions in hopes of improving how they use the airwaves that carry their wireless signals. The agreement could also ultimately affect how much money the FCC raises in January in its auction of spectrum, the agency's first major spectrum auction since 2008.
Such an agreement has been a key policy goal of FCC Acting Chairwoman Mignon Clyburn to help smaller wireless providers, such as regional or rural carriers, gain access to more and better devices to operate on their airwaves in the lower 700 megahertz band.
AT&T owns a band of frequencies in the adjacent block and by agreeing to "interoperability" of devices between its airwaves and the ones in the nearby frequencies, it gives manufacturers the incentive to make phones that would be usable for customers of smaller providers as well as the second-biggest provider, AT&T.
The airwaves in the 700 megahertz band are highly valued for their powerful signal.
"For folks in rural areas in particular, this is going to allow local providers to offer service not just on their systems but also on AT&T systems," said Harold Feld, senior vice president of consumer advocacy group Public Knowledge.
In some areas, he said, interoperability may lead to more roaming options or even give local providers a chance to grow into regional ones.
In announcing the ruling, Clyburn praised the collaborative efforts by AT&T, consumer advocacy groups, the Competitive Carriers Association and Dish, which helped smaller wireless carriers negotiate the interoperability deal with AT&T.
As part of the agreement, Dish promised to lower the power in the so-called E block of frequencies that it owns, to reduce the possibility of interference with signals sent on nearby frequencies, which are owned by other companies including AT&T.
In return for its promise to lower power, Dish gets more time and flexibility in building out the networks in that block of airwaves.
For Dish, the order is the first step in its strategy to grow as a wireless competitor and expand in mobile broadband.
Dish has separately also asked the FCC to delay the deadline for building networks on other airwaves it bought in 2012 and for more flexibility in how it could use them.
The FCC sets deadlines and requirements for how - and how quickly - the companies have to make use of the radio frequencies they own.
The agency is currently reviewing Dish's further requests, although it is unclear whether the new FCC chairman, Tom Wheeler, whose nomination awaits Senate confirmation, would rule to satisfy all of Dish's wants.
To sweeten the deal, Dish told the FCC that if the agency gives its nod to all of the company's requests, it would invest $1.56 billion in the upcoming auction of so-called H block frequencies, scheduled for January.
The investment would set the bar for other bids in the auction, whose proceedings will help fund a new network for emergency communications.
Congress has mandated that the FCC raise enough money to build the public safety network, which makes Dish's bid important as it could help avoid low offers or only one offer expected to come from Sprint Corp.