A federal grand jury in San Francisco charged yesterday that Jerry Alfred Whitworth, the sole remaining defendant in the Walker family spy ring, passed the Soviets technical manuals and design plans for the machines used to encode sensitive material -- a security breach that, together with other material allegedly supplied by Whitworth, would have enabled the Soviets to read secret Navy communications.

According to the indictment -- the fourth issued against Whitworth, 46, a retired Navy communications specialist -- Whitworth passed the information as recently as June 1983, while he was senior chief radioman aboard the USS Enterprise. While codes are changed daily, the complex coding machines themselves are not modified frequently.

In a press release, U.S. Attorney Joseph P. Russoniello said the indictment was the "result of new evidence which was not previously available to the grand jury." A source familiar with the case said the new evidence came from John Anthony Walker Jr., who pleaded guilty to espionage Oct. 28 and was in San Francisco last week to testify before the grand jury.

The earlier indictments of Whitworth alleged that he gave Walker "key lists" and "key cards" that are changed daily and used with "encryption" machines to encode and decode sensitive messages. Yesterday's indictment indicates for the first time that the material allegedly passed by the Walker ring included details about electronic coding machines -- suggesting that the Soviets would have been able to build replicas of the machines and make use of the key cards.

A source familiar with the coding technology said the manuals included diagrams for the circuits that are the key components of the coding devices.

Chief of Naval Operations Adm. James D. Watkins said in a briefing in June that the design of some secret Navy communications gear "probably has been lost" to the Soviets. A top Pentagon official said at the time that the Navy's worst-case scenario was that the Soviets could have received manuals on the coding machines themselves.

The coding gear used by the Navy is similar to that employed by the Army, Air Force and Marine Corps, according to sources, and the Defense Department announced in June that all the military services were assessing the damage that might have been done by the Walker ring.

Navy officials said yesterday they had not seen the new indictment and could not comment on it. Retired Capt. James T. Bush, associate director of the Center for Defense Information here, said the allegation that Whitworth passed information about the coding machines bore out the Navy's initial damage assessment.

"If you've got the machine and the keylists, then you've got everything," he said. "Then you've got a total breakdown of security."

Said Russoniello: "From the damage assessment, which is continuing, it would appear that this was one of the most serious security breaches that the United States has suffered since World War II. The cryptographic equipment and the keys permit access to the most sophisticated of our intelligence communications."

Tony Tamburello, one of Whitworth's lawyers, said the allegations involving the coding machines were "something that we've been talking about all along." The new indictment "obviously comes from what John Walker has said," Tamburello said, denouncing Walker's information as untrustworthy. He accused the government of "making a deal with a shark to go after a minnow."

The indictment alleged that Whitworth passed Walker classified information about cryptographic equipment and codes as well as Navy message traffic, on at least five occasions from August 1977 to June 1983 in Hong Kong, Manila and San Leandro, Calif.

The indictment did not detail what coding machines Whitworth allegedly passsed information about.

The indictment also for the first time discussed the evolution of Whitworth's alleged espionage conspiracy with John Walker. According to the indictment, the Navy colleagues met in 1974 in a San Diego restaurant, Boom Trenchard's Flare Path, and agreed that Whitworth would concentrate on obtaining classified information and Walker would be responsible for selling it to the Soviets.

They agreed to split the profits equally, the indictment said. Whitworth is accused of receiving at least $332,000 for his alleged participation in the spy ring.

Walker, 48, and his son, Navy Seaman Michael Lance Walker, 23, have pleaded guilty to espionage, and John Walker's brother, retired Navy Lt. Cmdr. Arthur James Walker, 51, was convicted of espionage.

As part of his plea agreement, John Walker, a retired Navy communications specialist, promised to divulge details about the scope and operations of the espionage ring and to testify against Whitworth.