When U.S. broadcasters switched to all-digital television earlier this summer, consumer advocates feared that minority and non-English-speaking viewers were at risk of losing access to the analog TV signals that carried news reports, emergency warnings and public safety information. If these viewers did not upgrade to digital TVs or converter boxes, they lost programming.

Now minority media groups are asking President Obama to address another broadcasting issue they say could leave radio listeners--particularly black and Latino audiences--in the dark.

In a letter dated Aug. 6, the NAACP, the Minority Media and Telecommunications Council and the Hispanic Telecommunications and Technology Partnership, asked Obama to address a new radio ratings system now used by Arbitron, which measures radio audiences.

These groups are part of the PPM Coalition, which includes the Spanish Radio Association and the National Association of Black Owned Broadcasters. They say Arbitron's Portable People Meter system, which requires sample listeners to carry cellphone-sized devices at all times to track which stations they tune into, undercounts minority stations' audiences.

"The toll on minority stations has been devastating to their ratings positions--costing between a 40 to 60 percent drop in ratings," the letter said.

The coalition last year asked the Federal Communications Commission to investigate the accuracy of Arbitron's ratings system, which is currently used in 20 U.S. radio markets. It points to Arbitron data showing that minority participants tend to carry the devices less frequently than the average sample listener in some markets. Therefore, the stations that appeal to minority audiences will appear to have fewer listeners, the coalition says, which could negatively impact the stations' advertising revenue. That could put some stations out of business and reduce diversity on the airwaves, the letter said.

In its June report, Arbitron said it is taking steps to increase participation in African American and Latino households. For example, it is creating new incentives to recruit more minority listeners. Arbitron added that many stations targeting minority listeners have actually increased their market rankings since the new system was introduced.

House Majority Whip Jim Clyburn (D-S.C.), Rep. Charles Rangel (D-N.Y.) and Edolphus Towns (D-N.Y.) have urged the federal government to help minority-owned stations stay in business. Minority broadcasters have met with administration officials to ask for emergency financial assistance to help the industry.

Last week, Pierre M. Sutton, chairman of Inner City Broadcasting Corp., said in an op-ed in the New York Daily News, "At a time when millions of African Americans and Latinos need information and opportunities to get jobs and build businesses, let's not pull the plug on black and Hispanic radio."

--Kim Hart