RKO General defended itself against allegations of fraudulent billing and other improprieties yesterday and asked the Federal Communications Commission to reverse a decision to revoke its 14 radio and television licenses.

A FCC administrative law judge ruled Aug. 13 that RKO was unfit to hold the licenses, which the company estimated to be worth between $400 and $500 million.

In a 95-page document rebutting the allegations, RKO said the decision was "extraordinary in the number of its errors, both factual and legal, and in the extravagance of its rhetoric."

A. William Reynolds, chairman of GenCorp, RKO's parent company, said in a statement released with the document that "fairness and equity demand that {the} FCC reverse the initial decision."

RKO, in its appeal, said the company has already "been penalized more than any other licensee in commission history" by the loss of its Boston station, WNAC-TV, in 1982 for lack of candor in disclosing financial information to the FCC during renewal proceedings.

"RKO has recognized that it made a serious mistake," the company said. "For nearly a decade it has sought to remedy the failings that led to the loss of the Boston license and to fulfill its responsibilities as a commission licensee."

Administrative Law Judge Edward J. Kuhlmann, in an initial decision that cited RKO for fraudulent billing, overcharging advertisers and destroying an internal audit report, said, "no case ever before decided by this commission presents dishonesty comparable to RKO's."

He recommended the FCC strip RKO of the licenses. If the agency were to do so, the company would be unable to operate those stations and would be left with only the physical hardware and property.

The stations are KHJ-TV, KHJ-AM and KRTH-FM, Los Angeles; WHBQ-TV and WHBQ-AM, Memphis, Tenn.; WOR-AM and WRKS-FM, New York; WRKO-AM and WROR-FM, Boston; WGMS-AM, Bethesda; WGMS-FM, Washington; KFRC-AM, San Francisco; WAXY-FM, Fort Lauderdale, Fla.,and WFYR-FM, Chicago.

RKO's problems with the FCC began more than 20 years ago. As each of its various licenses have come up for renewal, other companies have filed to take over the license. There are competing applicants for each of the licenses, and settlements are pending for three stations.