Fairness in Media, the conservative group supported by Sen. Jesse Helms (R-N.C.) and Rep. Phil Crane (R-Ill.), unveiled plans yesterday for a newspaper and television advertising campaign designed to encourage conservatives to purchase stock in CBS Inc. and to convince the public that the "CBS Evening News" and its anchorman, Dan Rather, are anti-Reagan and liberally biased.

FIM has said since January that it will try to gain financial control of CBS to end what it believes is a "liberal bias" in CBS network news coverage. FIM cofounder Jim Cain said the first advertisement would appear in today's Washington Post. He said the extent of future advertising is uncertain because he does not know how much money the group will be able to raise. But FIM cofounder R. E. Carter Wrenn said copies of the ad will be mailed to the group's 25,000 supporters, who will be encouraged to raise money to run the ad in their local newspapers.

Cain said the campaign probably also will be aired on cable television. Wrenn said the group would like to broadcast the ad on Ted Turner's Atlanta-based WTBS Superstation and other major cable channels.

Turner has launched his own bid for control of CBS, and Cain said yesterday that, while FIM believes Turner is a "preferable alternative to current management, we are conducting our campaign completely separately. If he succeeds in gaining control of CBS , we'll continue to urge conservatives to purchase CBS stock," Cain said.

The Washington Post reported in March that Turner told CBS lawyers he had held discussions with Helms and FIM about launching a joint takeover bid for the network. But when Turner announced his bid for CBS in April, he said he was acting independently.

"This is another step in an endless campaign to raise money for political purposes at the expense of CBS," said CBS spokeswoman Anne Luzzatto. "Fairness in Media has launched numerous gambits, but there is one common denominator -- to raise money for Sen. Helms and his associates."

FIM said it is launching the campaign in response to ads on CBS that say the network's news coverage has "objectivity, accuracy and reliabilty." George Schweitzer, vice president of the CBS broadcast group, said: "We have great respect for the intelligence of the American people. They decide each night what news broadcast they prefer. The fact that they freely and consistently choose the 'CBS Evening News' with Dan Rather over all other choices speaks for itself."

FIM's television ads were produced by Jefferson Marketing, a corporation controlled by FIM cofounders Wrenn and Thomas F. Ellis. Jefferson provides conservative candidates and causes with assistance in fund-raising activities, including direct mail, automated telemarketing and the production and placement of commercials.

Wall Street analysts estimate Turner's bid is worth about $150 a share. CBS stock closed yesterday at 118 7/8, up 3/8.