Superposition of Two Modulated Radio Frequencies

If two modulated radio frequencies are added, the envelope of the resulting signal can be found by means of a vector diagram. A number of envelopes corresponding to various conditions are shown. The distortions in the resulting envelopes are mainly due to phase shifts of audio frequency. Low percentage modulation helps to keep distortions small. The treatment applies to common-frequency broadcasting and to all cases in which the received signal consists of a direct and a reflected beam.