A Polish military court convicted and handed down prison sentences today ranging up to 4 1/2 years for organizers of Radio Solidarity, the clandestine station that pierced the state monopoly of the air waves during martial law last year to offer news from the political underground.

The guilty verdicts against Zbigniew Romaszewski, 43, a physicist who masterminded the operation, his wife Irena Zofia and seven others who assisted in the broadcasts ended what has been the most publicized prosecution of those who actively resisted martial law.

Romaszewski, a former national commission member of the now banned independent trade union Solidarity, has been active in Poland's democratic opposition since the mid-1970s. He was sentenced to 4 1/2 years in prison for violating martial law by continuing union activities and by spreading what the court declared was false information aimed at stirring social unrest and weakening Poland's defenses.

Irena Zofia Romaszewski, also a physicist, was given a three-year term. The other defendants received sentences ranging from seven months to 2 1/2 years, some suspended.

A three-member panel of military judges that presided over the four-week trial here described the jail terms as lenient in view of calls by the prosecution to sentence Romaszewski to eight years in jail and his wife to five years. Some violators of martial law who faced summary judgments last year received 10-year terms.

In the Radio Solidarity case, the judges said consideration was given to the fact that Romaszewski had no criminal record and to the positive character references he received from professional colleagues. The judges said health and family factors also weighed in the sentencing, according to witnesses at the trial. It was closed to western media and most Poles.

A show of leniency would serve efforts by the government of Gen. Wojciech Jaruzelski to avoid appearing vengeful against opponents.

Radio Solidarity went on the air April 12, on the eve of the start of the fifth month of martial law. It confounded authorities and appeared to boost the morale of the opposition to the military rule--providing information about protest activities and police actions.

It broadcast about a dozen times, using taped messages and transmitters placed at the top of buildings, and gave rise to underground radios in Wroclaw and Poznan.

Police captured two of Romaszewski's assistants in June as they carried a transmitter out of a downtown building. On July 5, security agents caught Irena Zofia Romaszewski and a number of others in a raid on an apartment. Her husband eluded police until Aug. 31.

Although the government has arrested others of the Solidarity underground leadership, it continues to issue calls for resistance.

Romaszewski never denied his involvement with Radio Solidarity but told the court he did not believe himself guilty because he had acted for ideological reasons. He did rebut the charge that the radio had broadcast false information.

The court cited as examples of false statements: that internment was not different from arrest; that the ruling military council was driving the country to ruin; and that drugged riot police had been turned loose on demonstrators.