Frederick County is putting itself up for sale, with its economic development authorities touting the county as a "Golden Triangle, a mecca for the nation's research, communications and electronic businesses."

The county is passing along to corporations what it calls "ambassador packets" showing that Frederick County lies in the middle of things, halfway between Washington and Baltimore. With its "country charm," the packets go on to say, Frederick County is "ideal for high technology businesses in campus-like" settings and manufacturing sites only 45 miles from Capitol Hill.

With the recession easing off, the county's economic planners feel their hopes for a corridor city along I-270 may materialize after all. Some land along the I-270/Rte. 85 corridor that sold for $10,000 an acre a few years ago is now selling for $80,000 an acre, said Pollie Sliger, president of the Frederick County Board of Realtors.

"We are starting to see real estate speculators take an interest," Sliger said.

County officials became concerned last year when they installed water and sewer lines on the I-270 corridor and people weren't buying. But recently, the Kiplinger Letters publishing corporation bought a $1.6 million farm tract in Urbana that the company says it will keep for speculation.

Lewis W. Bruchey of the county's economic development authority says the county is going to designate 18,000 acres for commercial development in the next 20 years. Most of it is in the southern part of the county, along I-270, Rte. 85 and old Md. 355 in Urbana, or near the Frederick Municipal Airport east of Frederick.

Bruchey said the county is currently wooing about 25 firms, including a "large manufacturing conglomerate" that would yield a $40 million investment and bring 600 new jobs to the county.

The county brought in 10 new businesses last year with a capital investment of $6 million, and most of them are locating near the airport.

The Federal Aviation Administration has targeted $20 million to expand the airport's landing system and has just given another $3 million to the town of Frederick to expand the runway to 5,200 feet so that planes as large as a Boeing 727 could land there. According to FAA records, there were more than 160,000 landings and takeoffs there last year.

Airpax-North American Philips Corp. is making a $5.5 million expansion of its building at the airport. Its 69,000-square-foot building, which houses 360 employes now, will expand by another 88,000 square feet and open up 532 more jobs. Three other large firms, including Fairchild Industries, also will be expanding their operations here soon, Bruchey said.

The county recently purchased a Walkersville fish farm to expand the county's water system north of Frederick, where the county has zoned 700-units of single family homes and town houses and where another 600 units are slated to be built in the late 1980s.

Walkersville Mayor Orley R. Bourland Jr. said that unless the county brings in bigger businesses, and their tax base, his town will not be able to afford fire and school services for its new residents.

A comprehensive development plan for the county will be turned over to the commissioners for final consideration in August.

In Frederick City, the plan calls for 1,286 acres to be designated for industrial development or mineral mining along Gas House Pike to the Moncracy flood plain east and north of the airport.

The plan calls for a 1,963-acre office-research complex along Hayward Road, where an intersection is proposed to ease any traffic congestion. East of the city at Tulip Hill, a park will serve to buffer the planned neighborhoods from the airport and industrial development.

The City of Frederick already has preserved 452 acres of farmland in the northern part of the city, and 17,682 acres in Frederick Valley will be zoned for farming.

In the southern end of the county, planners are earmarking 28,000 acres for homes, mostly in the Middletown, Urbana and New Market areas. The county is expecting its population to increase 37 percent, to 157,000, by the year 2000.

County officials say they will place small ads in The Washington Post and The Washington Business Review next month in an effort to emulate the success of Fairfax County, which successfully wooed Mobil Oil's corporate headquarters from New York in 1979, and more recently, Fairchild Industries from Montgomery County.

Mark Friis, senior county planner, said it is unlikely that Frederick County will change overnight into another Montgomery or Fairfax county, especially on an economic development budget of $106,000, compared with $1 million in Fairfax.

Not everyone thinks that would be a good idea anyway. Frederick County still considers agriculture big business. Its 528 dairy farms make up a $70 million industry annually, producing the equivalent of more than one billion eight-ounce glasses of milk. In recognition of that, the comprehensive plan calls for three-fourths of the county land to remain zoned for agriculture.