Every local broadcast station has a repository of documents about political advertising that you have a legal right to see but can do so only by going to the station and asking to see “the public file.”

These paper files contain detailed data on all political ads that run on the channel, such as when they aired, who bought the time and how much they paid. It’s a transparency gold mine, allowing the public to see how campaigns and outside groups are influencing elections.

But TV executives have been fighting a Federal Communications Commission proposal to make the data accessible online. They say making the files digital would be too burdensome — it “could well take hundreds of hours for a single station,” according to comments filed with the FCC by the National Association of Broadcasters.

Others have taken their case a step further. As reported by Bloomberg Government, Jerald Fritz, senior vice president of Allbritton Communications, said in an another FCC filing that online availability “would ultimately lead to a Soviet-style standardization of the way advertising should be sold as determined by the government.” (NPR’s On the Media did an excellent segment recently on broadcasters’ opposition to the proposal.)

We tend to like the idea of public data being online. Since TV stations won’t put it online themselves, we decided to do it ourselves — and we want your help.

Working with students at the Medill journalism school at Northwestern University, we looked at five local stations in the Chicago market.

You can explore the results yourself: Here are detailed breakdowns of when the ads aired, during which programs, and how much each spot cost: Read the documents from the local affiliates of ABC, NBC, CBS, FOX and CW.

Big thanks to Medill students David Tonyan, Julie O’Donoghue, Vesko Cholakov, Safiya Merchant and Gideon Resnick, who visited the stations Monday.

We intend to enlist more readers in checking their local stations as the election campaigns slog on. The general election is likely to usher in even greater spending, and such spot checks could keep an eye on how big spenders are influencing the election. If you’d like to join in, please fill out this form.

Campaigns and super PACs are required to report their spending on independent expenditures to the Federal Election Commission within a day or two, but they often just report how much they paid ad-buying firms, which can disguise how much actual ads cost and where they’re airing.

What’s more, the files could be a window into what may be otherwise undisclosed spending by “dark money” nonprofit groups that are playing an increasing role in the elections .

For our experiment, we asked our Chicago volunteers to check on spending by five super PACs that individually support Mitt Romney, Rick Santorum, Ron Paul, Newt Gingrich and Barack Obama. There were no records of spending in Chicago by four of them, but Restore Our Future, a pro-Romney super PAC, advertised on all five stations. The super PAC paid the five stations about $800,000 in the past month.

As our PAC Track interactive chart shows, Restore Our Future has spent more than twice as much as any other PAC so far — nearly $37 million.

Medill student O’Donoghue said getting the files from the ABC station took her about half an hour, most of which was spent wrestling with the copy machine.

Tonyan, another graduate student, said he spent 15 minutes at the CW affiliate, plus a 15-minute drive.

Both said the station employees who helped them were friendly and accommodating. We encountered the same when I visited five stations in New York, Missouri and Florida. Typically, a station employee will simply show you the room where the files are kept and let you dig in.

Such visits don’t seem to happen often. A log at the New York CBS affiliate showed only six registered visitors since October 2011.

The Campaign Media Analysis Group, a unit of Kantar Media, tracks ads that have hit the airwaves and estimates what they would cost, but the company charges high rates to obtain the information. The Wesleyan Media Project publishes some CMAG data.

Rich Robinson, executive director of the Michigan Campaign Finance Network, found that $70 million in advertising had been unreported from 2000-10 in Michigan. He got that number by personally examining public files, at one point driving 14 hours for a 15-minute visit to a station.

He told the FCC: “I can testify to you, unequivocally, that the threshold of effort necessary to report this important public interest story is too high for every news organization in Michigan, except mine.”

Which is why we’re asking for your help.

Thanks for your interest; this project has been archived and we are no longer accepting volunteers.