Vatican radio has erected the largest rotating antenna in the world to strengthen the voice of the pope around the globe - and try to gain the upper hand on Communist jammers in Eastern Europe.

The new transmitter, with 500 kilowatts of power for short wave, is expected to become operational by summer, Vatican radio officials said. The tower, 260 feet high, surpasses for short wave.

The new transmitter and the increased power of Vatican radio could bring sharp reaction and increasing jamming from the Comunist lands of Eastern Europe.

In a recent visit to Italy, Soviet editor Alexander Tchaikovsky of the weekly Literaturnaya Gazeta mentioned Vatican radio as one of the western stations that beam news of dissidents in Russia.

And Vatican radio recently announced that a Czechoslovakian priest was assigned to a "re-education" institution for two years for exhorting his parishioners to listen to Vatican radio broadcasts.

The Rev. Sabino Maffeo, technical director of Vatican radio, said the new transmitting tower, 10 miles outside Rome, is designed "for the diffusion of the message of Christ and the words of his vicar to listeners in the entire world, particularly for those in nations where the church does not enjoy full liberty."

The Rev. Pasquale Borgomeo, program director, said the East European jamming forces rthe radio occasionally to switch frequencies, but that the jamming is not at the level it reached during cold-war days.

"The radio," he added, "has become less aggressive in line with the Ostpolitik (opening to the East) of Vatican diplomacy. We abstain from specific attacks (on nations) and even quote (Communist) publications in our newscasts."

Father Borgomeo also said Vatican radio is more objective than government subsidized radios, such as the Voice of America and Radio-Free Europe, because it emanates from a citystate founded on moral principles and its newscasts quote independent news agency dispatches. It also carries religious news and popular music.

Soviet dissident Yuri Orlov has estimated that one-fourth of Soviet city-dwellers listen to foreign broadcasts. And Soviet leader Leonid I. Brezhnev has remarked that such broadcasts "pioson the atmosphere."

The radio, also transmitting on the medium wave for the Mediterranean and FM for Rome, is directed by Jesuits. It employs 250 persons and an equal number of part-time workers for its 225-hour-a-week programming in 33 languages.

Pope Pius XI inaugurated the radio in 1931, with a transmitter designed by Guglielmo Marconi. The tower on a rolling Vatican hill grew to reach every corner of the world and acquired the nickname of "Dito del Papa," or the pope's finger.