The complete Maxwell‐Vlasov equations together with feedback are analyzed in the quasi‐homogeneous case, using the Nyquist criterion. A class of feedback loops, satisfying sufficient conditions for stability but depending on the wave number k, is found. If the instability satisfies certain properties, a subclass of feedback loops, independent of the wave number, can be constructed. The classical amplification‐delay feedback, generally used in experiments, does not belong to the subclass; and therefore designing an adapted feedback loop is of importance. Applications of the general theory to the low‐frequency electrostatic microinstability and the double beam instability are given.