High-tech (and high-cost) car phones roll today in Chicago

Today Chicago leaps to the forefront of a technological revolution in the United States. From street level, the change will be barely noticeable. More busy executives will whiz about town with a telephone in their car. And they'll probably complain less about busy signals.

But today's landmark - the start-up of the nation's first commercial mobile phone service using cellular radio technology - means much more than that, experts say. It heralds innovations that will reach into corporations and households.

''Cellular is the first type of a new technology - called telephone without wires - that will eventually replace the wireline (traditional telephone) network,'' says Stuart Crump Jr., editor of Cellular Radio News. As technological improvements come along, these telephones will become increasingly smaller. Ultimately, they may end up in consumers' shirt pockets or on their wrists, Mr. Crump adds.

''We need some sort of breakthrough'' to make that possible, cautions John S. Bain, a vice-president of research at Lehman Brothers Kuhn Loeb. But if the technology keeps improving the way it has, people may look back at current telephones ''the same way we look back at the pocket calculator.''

The immediate benefit will be for business people who have telephones in their cars. Entrepreneur Jules Furth, for example, packs a mobile phone and a CB radio in his silver Cadillac, and looks forward to getting even better service.

''I have a mobile office,'' exclaims Mr. Furth, who was one of 2,000 trial users of the Chicago cellular system, an experiment begun in December 1978. ''It's a far superior service than what we had.''

Cellular service will open the way for many more people to have car phones.

The most advanced conventional service usually operates with one transmitter powerful enough to serve the whole city. Typically, only 12 to 14 channels are available, which means the system can only handle 12 to 14 calls at a time.

A cellular system, on the other hand, operates with a network of transmitters , which are strong enough to serve only one part of the city. That way different sections of the city can reuse the same frequencies. When a car travels from one sector to another, computers automatically hand the call off to another transmitter.

According to one estimate, cellular service can handle up to 50,000 calls during a busy hour in a major metropolitan area. The best conventional service, by contrast, is limited to 1,400 calls per hour.

To be sure, talk in the fast lane doesn't come cheap. The phone alone is likely to cost from $2,200 to $3,500. And average monthly charges will total some $150 to $200, according to Ameritech Mobile Communications Inc. The company , currently a regional subsidiary of American Telephone & Telegraph Company, inaugurates its service today, after receiving Federal Communications Commission (FCC) approval last week.

And some people, like Evan Richards, a vice-president of engineering and operations at Ameritech, have been initially skeptical about whether they really want to have telephones in their cars. After a few months of the service, though , Mr. Richards says he is sold on it.

''I find myself handling a lot of things I wouldn't get to (normally),'' he says. And on those days he doesn't want to be reached in his car, he turns the phone off.

How well will the new phones catch on? That depends on who you talk to. Estimates for 1990 range from 800,000 to 2.5 million (which would mean that more than one out of every 100 Americans had a mobile phone). One big factor will be how quickly competition can bring the costs down. Many observers estimate the cost of a mobile phone will be halved in five years.

At last count, 18 firms were planning to manufacture mobile or portable phones, Crump says.

And the number of applications to the FCC to offer cellular service in various cities has been surprisingly large. Each major city is to be served by two competing firms - one telephone company and one nontelephone company. But for the two slots in Austin, Texas, for example, the FCC received 28 applications.

Some observers estimate that the 30 largest cities will have cellular service within a year.

In Chicago, Ameritech will likely square off with Rogers Radiocall, which already operates conventional mobile phone services in Chicago. The FCC has not yet allowed Rogers to build its network in Chicago, and there is some concern that Ameritech will have a head start in providing service.

But, counters Bud Kahn, executive vice-president of Rogers, his network could be ready ''a lot sooner than most people think.''

Regulatory delays have held up cellular service throughout the US, while several countries - including Japan, Norway, Sweden, and tiny Bahrain - have systems already operating. And experts question whether the US can catch up.