The outlook for the fixed-income markets over the next couple of months is not good. A seemingly determined policy by the Federal Reserve Board to fight inflation with a restrictive monetary policy led by higher interest rates will send bond prices tumbling.

Since Paul A. Volcker has been Fed chairman, the federal funds rate has risen about 100 basis points. This upward thrust has sent shock waves through the various debt markets but tax-exempts have been hit the hardest.

Until mid-August, the tax-free market had outperformed the other bond markets with good supply and attractive returns for investors. However, dealers had become top-heavy with inventory and, as the short rates were jacked up by the Fed, price adjustments had to be made in the tax-exempt area. Buyers fled the marketplace, and the dealers were left with unsold bonds.

Price-cutting began, and yields jumped up. A block of unsold triple-A California general obligation bonds due in the mid''80s that initially sold on a 5.00 percent basis sold last week on a 5.50 basis for a loss to underwriters of $28.75 per $1,000 bond.

Long tax-exempt dollar bonds now were being offered with 25 basis points more yield than two-weeks ago (a basis point is one-hundredths of a percentage point).

To put it all in perspective, the Bond Buyer Index moved from 6.16 percent in mid-August to 6.47 percent last week, a significant price adjustment.

Price declines occured in Treasurys and corporates as well. If the supply should increase dramatically, these markets would decline sharply.

The key to the entire picture right now is short-term interest rates. The Fed tightens or eases

Lebherz has 19 years experience in fixed-income investments. credit through the federal funds rate, which it influences by purchasing or selling securities. The main thrusts of its policy are carried out through this short-term rate which, in turn, affects all other short-term rates and influences long-term rates as well.

Consequently, however the Fed reacts to the economy, inflation, the growing monetary aggregates and the dollar situation will be reflected inshort-term rates first. Currently, these rates are headed higher.

The best investment posture now would be a short position, like a money market fund which pays more than 10 percent. As attractive issues that fit your investment objectives are marketed, shift into these new issues.

Once again, the tax-exempt area especially will be offering attractive merchandise over the next two months.