Description / Abstract: DO-186B recommends standards and test procedures for airborne VHF communication transmitters and includes test conditions and procedures for installed equipment. This update incorporates Changes 1 and 2 of DO-186A and establishes performance standards for equipment designed for offset carrier operations, i.e., equipment classes A and C. An exclusion band to enable a successful and appropriate Radio Frequency Susceptibility Test (DO-160 Section 20.0) is defined. The document also includes class E receivers which are able to be used in an 8.33 kHz channel separation environment. This document supersedes DO-186A.