``The communication was horrible and there's no disputing that,'' said Tom Manley, health and safety officer for the firefighters' union. ``You didn't get the necessary transmissions being heard. Some people heard, some people didn't.''

City officials have attributed part of the problem to the destruction of equipment called repeaters, which boost radio signals. The repeaters were mounted high in the trade center and in commanders' cars to amplify and retransmit signals. They were destroyed when the hijacked planes struck the buildings and debris crushed the vehicles below.

Firefighter unions said that long-standing radio problems in high-rise buildings also played a role.

Both say the new, $14 million system appears better suited to situations that could have hundreds of personnel from different agencies performing complex operations at great personal risk.

The handheld Motorola radios being tested for a late-summer debut operate at higher frequencies better able to penetrate concrete and steel than the radios in use Sept. 11, company and fire officials say.

They are expected to be augmented by new repeaters in 60 high-rise buildings, and radio antennas in subway tunnels, where firefighters also have long had communication problems.

Unlike the models they replace, the new radios are compatible with police, Office of Emergency Management and other city systems.

At ground zero on Sept. 11, one emergency official who did not have a fire department radio could not broadcast an alert that the north tower was in danger of collapsing. Instead, he had to send a subordinate racing across the trade center plaza to hand-deliver the message to a fire chief inside.

``Nine-eleven, of course, highlights some of the communication difficulties that we had,'' fire department spokesman Frank Gribbon said. ``We sort of knew all of this prior to 9/11, but after that event you see how critically important it is.''

The new radios can be programmed to operate on dozens of radio channels, preventing the fire department's usual single fire-scene channel from being congested during a large-scale incident such as the trade center attack.