RADIO DISCONNECT REALLY HERTZ

YOUR PURSE OR WALLET is snatched while you're waiting for a SEPTA train. Luckily, SEPTA police officers are nearby.

Not so luckily, they may be unable to communicate with police officers above ground, thanks to a long-standing radio disconnect between SEPTA police, who use the 400 megahertz band, and the rest of the city, which uses an 800 megahertz band. A fancy name for it: "interoperability."

The need for officers to communicate when chasing a purse snatcher or other criminal underground, multiplies when a larger tragedy like 9/11 is considered.

For now, the quick, simple fix is that SEPTA has provided the city 50 walkie-talkies tuned to its frequency; 30 have gone to firehouses near SEPTA stations, and 20 to police.

It's not pretty, but it will have to do until a much more expensive solution can be built.

That more permanent solution lies in a keep-your-fingers-crossed request to the Department of Homeland Security.

Twenty-three million dollars, please.

The city is expected to make such a request when it files an application to the department for grant money, due in early April.

That would bankroll the installation of cable, or fiber optics, through 27 miles of SEPTA'S underground system. But a massive project has the potential to turn into a mess.

New York provides an unfortunate example.

Ten years ago, that city began a huge reconstruction project to replace an outdated radio system so Metropolitan Transportation Authority cops could communicate with city cops on the street.

It was completed last October, to the tune of $140 million. But now, according to a story in the New York Times, the system hasn't been turned on. It has interference problems and drop-out zones, issues that may cost $20 million more to fix.

For a tool so vital to rescuers and law enforcement, modernizing radio communication appears to be a huge challenge for cities.

Two years ago, a new $54 million city police radio system here had problems which temporarily knocked the radio off the air. Most of those glitches have been fixed.

Smooth communication between police below and above ground is crucial. Let's hope those who dole out Homeland Security dollars agree. *