On Oct. 19, two days after Republican Rudy Boschwitz announced that he would run against Sen. Wendell R. Anderson (D-Minn.) next year, Anderson sent a radio tape to 122 Minnesota stations jabbing his new opponent, a Minnesota businessman.

One Anderson complaint: that Boschwitz was buying advertising time on radio and television stations a year before the election.

"Anyone that has the financial resources and the money to put on a radio and television campaign more than a year before the election." Anderson said on his Senate tape 'is someone to be reckoned with."

But the complaint had a slightly hollow ring - because Anderson's tape was prepared at a bargain rate in the Senate Recording Studio, a $1.6 million facility in the Capitol's basement run by 17 Senate employees who cost the taxpayers $370,000 a year.

The Senate Recording Studio - and the House has one like it - is but one of the perquisites incumbent members of Congress have accumulated over the years.

Many of these "perks" have one thing in common - they make incumbent increasingly visible to the electorate and thus more difficult to defeat at election time.

Officially, of course, the purpose of these perks is not political. It is to assist the members in their duty as officeholders to communicate with their constituents.

But, as the Senate Recording Studio indicates, the distinction is not always clear. The studio's financing is illustrative: both taxpayer and campaign funds are mixed in its operation, and, as Senate Sergeant-at-Arms F. Nordy Hoffmann noted at a little-publicized Rules Committee meeting last July, "the law does not specify" that the studio be used for official purposes only.

"We do not monitor now," said Hoffmann, who supervises the studio, and he agreed "absolutely" that it would be difficult to determine what is official and what political.

Although members and their staffs continue to maintain that the tapes they turn out are official, most of them pay for the studio fees and tapes out of campaign funds.

Then they almost always send both radio and television tapes out under their frank and include a return postage sticker that is also franked. Thus the government pays for transporting material that was produced by campaign funds.

In Anderson's case the Oct. 19 radio tape was paid for from his campaign funds. But because of its obvious political content, he decided not to use the frank - as he usually did for radio tapes. In this case he used political funds.

Between June and September, Anderson's campaign committee reported it spent $2,500 in the recording studio.

Anderson, since August, has done a weekly 4 1/2-minute radio program that is sent free to Minnesota stations. On it he answers questions posed to him by his press aide, Robert Woodrum.

As Woodrum now describes the Oct. 19 program, the question about his opponent was "legitimate news" of the kind radio stations wanted covered on such a program.

In the biweekly television question-and-answer session Anderson had done immediately before recording his radio session, reporters from seven of the eight Minnesota stations that participated in the call-in format asked about Boschwitz.

The idea for the radio program, Woodrum said, came from a tour he made last summer to minnesota radio and television stations.

TV men wanted a flexible telephone interview format, one where they could call questions in to the senator while he was in front of a camera, record his answers and have the tape flown to them for immediate use.

The Senate Recording Studio is set up to handle just such a format, and it's regularly used by several senators along with Anderson.

A quick tour of the facility, located in part of the Capitol basement that once was the old Senate subway station, shows it is readily adaptable to any number of programs.

There's the Capitol backdrop that makes it appear you are in an office elegant gold curtain or a plain gray one.For interview programs there are chairs for guests and for personal statements there is a desk or podium, with or without a bookcase or fire-place background.

The facility also has a film studio and two radio studios. Since most members send their tapes statewide, the copying facilities are impressive. Six copies of a television program can be made simultaneously and eight radio tapes can be done at once, at speeds faster than they were recorded.

Prices are cut-rate. It cost $70 for studio time to do a 30-minute program, far below what is charged at a commercial facility.

According to Senate aides, at least one-third of the members use the recording studio on a weekly or biweekly basis.

On Nov. 8 for example, when the, Senate was not in session, eight members made use of the television facilities. Three of the eight are up for re-election next year and do regular shows.

The day before, Sen. Sam Nunn (D-Ga.) who also is running for re-election next year, did his monthly 30-minute interview program. In it he questions someone from Washington who is involved in a major policy area. Nunn's guest for the Nov. 7, session was Sen. Henry M. Jackson (D-Wash.) and the discussion was on energy, since Jackson chairs the Senate Energy Committee.

The Nunn show goes to all of Georgia's education television stations, and, according to Nunn's press aide, was originally requested by them.

Nunn also sends it to several commercial stations and they use it.

The Macon television station, for example, often uses a chunk of the show, which features Nunn answering questions from an aide about issues current that week. The radio end of the same station occasionally takes one segment for use on news shows over the weekend, since the tape arrives on a Thursday or Friday.

"We put Nunn's franking label back on," a Macon radio man said recently, "and send it back."

Senators want the radio and television tapes returned since they can be reused and are the most costly part of the studio usage.

Not all Senate aides promote use of the studio. As one put it recently, "TV news directors are turned off by a canned tape or film in front of the Capitol background . . . Those tapes are not as effective as other means to show the ordinary and necessary business of being a senator."

In the year a senator is up for re-election, the equal time provisions of the law make the sending out of free tapes less attractive.

"Our business is off election years," Charles Jones, director of the Senate studio said recently, "because the member has to list the expense as part of his campaign."

In other years, however, it gets substantial use and many seasoned Senate campaigners say re-election is often decided by a member's campaigning one or two years before election time.