It was a gargantuan feat for ABC's "20/20" to get film footage of Frank Sinatra's Egyptian concert on the air last Thursday night, only three days after he had sung in front of the Sphinx.

But all they heard from Sinatra was a call of complaint from his lawyer, Mickey Rudin, the next day. "Ol' Blue Eyes" was unhappy about the amount of time actually devoted to his singing during the segment.

Too little?

No, too much.

Rudin accused ABC of violating their agreement with his client by using 15 percent more singing time than previously agreed upon.

One network source says that Sinatra was hoping to sell the entire concert in Cairo to one of the three networks and only agreed to ABC'S "more talk than vocalizing" segment to promote that deal. Now he feels, the source says, that his show is less marketable.

Efforts to reach Rudin last night for comment were unsuccessful. . .

"The Iron Man of Watergate," G. Gordon Liddy, is jogging and weightlifting and taking long naps to get himself in shape for a month-long tour to promote his new spy thriller, "Out of Control." Talk-show hosts should ask him whether he thinks the 1980 election campaign is going to be any dirtier than in his dirty-tricks days. Addressing himself to the subjects of Chappaquiddick and Hamilton Jordan's image troubles, Liddy said recently: "I think it is ultimately going to come down to whether someone is qualified to drive the Indianapolis 500 or write an updated Emily Post volume on good manners" . . . .

Reporters are beginning to gather on Joan Kennedy's Boston doorstep. One reason she has not been more visible recently is the illness of the Kennedy cousin who was her constant companion through so many campaigns.

Sally Fitzgerald, one of the original Boston "Pol Molls," who perfected tea-party politics for the Kennedy women, has been hospitalized, and Joan Kennedy has been keeping a bedside vigil that caused her to miss at least one scheduled public appearance with her husband. . .

Marlo Thomas and Phil Donahue invited as a twosome to see the pope at the White House, went to dinner afterward to the Sans Souci. . .

Jacqueline Kennedy Onassis' mother, Mrs. Hugh Auchincloss, according to neighbors, was asking $1.4 million for her Georgetown house when one prospective buyer took a tour recently. Ironically, she really doesn't need the money now that she is remarrying later this month. For a while, she and her late husband had suffered such serious financial setbacks that one relative claimed they "really needed" his Social Security check . . .

Back home, under the Ayatollah's puritanical regime, the robbery would have probably gone unreported because adultery is a more serious offense than theft. But an Iranian businessman visiting here who had ties to the Shah's government called police when a girl he met in his hotel room made off with $16,000 in cash and valuables. She lifted a wrist watch and a pocket watch, each worth $7,000. . .

How could an old song-and-dance man resist? When the waltz music started at the Polo Club the other night, there was former senator George Murphy gliding around the floor. . .

Former GSA administrator Jay Solomon is carrying a "Kennedy in '80" button in his jacket pocket, but hasn't pinned it to his lapel yet.