RCA Corp.'s second-quarter profits edged up 2 1/2 percent from a year earlier and revenues rose 5.1 percent to a record $2.06 billion on higher earnings by the communications and transportation units, the company said yesterday.

Profits of RCA's electronics unit fell, however.

Meanwhile, R.J. Reynolds Industries and Raytheon Co. posted higher second-quarter earnings and sales, and Georgia-Pacific Co. said its profits increased while sales declined.

RCA said it earned $60.5 million (58 cents a share) in the second quarter compared with $59 million (56 cents) a year earlier. Revenues climbed to $2.06 billion from $1.96 billion.

First-half net income rose by 19.8 percent to $121 million ($1.15) from $101 million (89 cents) in the comparable 1981 period, as revenues set a record at $4.02 billon, up from $3.90 billion.

RCA noted that its first-half profit included a net gain of $29.1 million in the first quarter from its program of divesting certain assets, including a greeting-card maker and other manufacturing operations.

Higher second-quarter earnings by RCA's communications segment were paced by its domestic satellite unit. Earnings also rose at its NBC television unit, mainly because of improved operations of its TV network and its owned and operated TV stations. RCA said NBC's results would have been higher except for "heavier than anticipated costs involved in news coverage of such events as the Falkland Islands and Middle East conflicts."

RCA's Hertz unit also had higher earnings, mainly because of improvements in its car rental and truck operations, RCA said.

But the company said that its electronics group continued to struggle amid an ailing economy despite improvement by the records and government systems operations.

One problem is RCA's SelectaVision videodisc player, which transmits movies and other programs from a grooved disc onto a TV screen. The company spent millions of dollars to develop and bring the players to market last year, but sales have been far less than RCA hoped, and it responded earlier this year by cutting the list price to $349.95 from $499.95. Since then it has introduced three other models ranging in price from $299.95 to $449.95.

RCA would not break down sales of the players in the latest quarter, but said earnings by its consumer electronics unit were hampered by heavy inventories of video products that "stimulated severe price competition . . ."

It also noted, on the other hand, that consumers have been purchasing an average of 32 video discs during the first 12 months of owning a player, which RCA said is "three times greater than originally anticipated."

R.J. Reynolds Industries Inc. had an 8 1/2 percent gain in earnings in the second quarter on a 5.1 percent rise in sales.

Domestic and international tobacco sales, foods and beverages and transportation revenues all were up, but energy revenues were down significantly, Chairman J. Paul Sticht reported yesterday. He said the cigarette business had both better unit sales and better price margins.

Net income was $295 million ($2.74 a share) on sales of $3.12 billion compared with 1981 second-quarter net income of $199 million ($1.82) on sales of $2.97 billion.

First-half profits were $480 million ($4.43) on sales of $5.988 billion, up from $387 million ($3.54) a year earlier on sales of $5.74 billion.

Raytheon Co. earned $85.8 million ($1.02 a share) in the second quarter, up from $84 million ($1.00) a year ago, as sales rose to $1.427 billion from $1.423 billion.

First-half profits were $165.2 million ($1.96) on sales of $2.843 billion compared with $157.2 million ($1.88) a year earlier on sales of $2.73 billion.

Strong government and commercial electronics business produced the gains, the company said.

The order backlog rose to $6.146 billion from $5.745 billion. About $2.599 billion of the backlog was funded by the federal government.

With the aid of revenues from the sale of oil and gas royalties and tax leasing benefits, Georgia Pacific Corp. earned $71 million (66 cents a share fully diluted) in the second quarter, up from $55 million (51 cents) a year ago, in spite of a drop in sales to $1.415 billion from $1.443 billion.

The company said its basic forest products business remains severely depressed.

First-half profits rose to $226 million ($2.08) from $107 million (99 cents) a year ago solely because of an accounting change on investment tax credits. Without these credits, first-half earnings were only 91 cents a share. Sales dropped to $2.614 billion from $2.791 billion.