Mutual Broadcasting System, an Arlington-based national radio network with 950 affiliates, reached an agreement yesterday to buy WHN in New York City for $14 million -- the second highest amount ever offered for a radio station.

If approved by the Federal Communications Commission, Mutual's acquisition of WHN would give the network its second owned and operated station. The only other radio station sale that exceeded the proposed WHN purchase price was Cox Broadcasting's acquisition of KFI in Los Angeles for more than $15 million several years ago.

Currently, Mutual is swaiting FCC approval for the purchase of its first radio station -- WCFL in Chicago, which the network has agreed to buy from the Chicago Federation of Labor for $12 million. Mutual, which began network operations in 1934, previously has not owned stations, and a spokesman said yesterday the network's current affiliation in New York City with WMCA would not be altered.

WHN is one of the top-ranked stations in the nation's largest radio market. Its format consists of the only country and western music diet among the city's larger stations. Currently WHN is the fourth-ranked New York area station for adults aged 25 to 49, and is seventh ranked overall for 24-hour-a-day broadcasting.

Mutual is buying the 50,000-watt station from Storer Vroadcasting Co. of Miami Beach. Fla., which announced plans last December to sell all of its radio stations.

Last week, Jefferson-Pilot Broadcasting Co. of Charlotte, N.C., agreed to buy two radio stations in Miami from Storer for $12.5 million. Subject to FCC approval, Jefferson-Pilot will acquire WGBS-AM and WLYF-FM. The proposed purchase would bring to 11 the number of radio stations owned by Jefferson-Pilot, whose properties include WWBT-TV in Richmond; WBT-AM, WBCY-FM and WBTV-TV in Charlotte; and stations in Greensboro, Wilmington, Atlanta and Denver.

The nation's largest radio network, Mutual recently signed WTOP in Washington as its local affiliate.

Mutual moved here from New York City in 1972 and currently operates from studios and offices in Rosslyn.

In 1977, the network was purchased by a subsidiary of Amway Corp., a direct marketing home care products firm based in Ada, Mich. Privately owned Amway, with some 300,000 distributors worldwide and annual sales of about $500 million, has since launched a major effort to revive and expand Mutual.

In another development yesterday, the Outlet Co., owner of WTOP since last summer, announced plans to buy WIOQ-FM in Philadlphia from Que Broadcasting Co. The station, located in the nation's fourth-largest radio market, would become Outlet's 10th broadcast property.

Bruce Sundlun, Outlet president, said the acquisition would be for $5.5 million in cash and $500,000 for a noncompetitive covenant. Outlet is a retail and broadcasting firm in Providence, R.I., that also owns the Philipsborn womens clothing stores in the Washington area.

General Electric Co. and Cox Broadcasting Corp., meanwhile, have signed a definitive agreement to merge Cox with G.E.'s broadcasting and cable television businesses in one of the largest broadcasting transactions in history. The final agreement provides for a tax-free exchange of 1.3 shares of G.E. common stock for each share of Cox common.

Both companies added a stipulation to their previously announced tentative agreement that would give Cox owners between $65 and $72 worth of G. E. common shares for each share of Cox common stock. Under the new agreement, those figures will apply only if the transaction is closed before Sept. 30. After that date, Cox owners would receive between $68 and $75 in G.E. stock.