Rca1948FrequencyModu.. - The New Jersey Antique Radio Club

COMMON- AND ADJACENT-CHANNEL INTERFERENCE 325Phase-Angle VariationsThe two signals e i sin ut and e 2 sin (w + 2ir\x)t are in phase when t = 0.Since the frequency of the second signal is higher than the frequency of thefirst signal, this means that a vector representing e 2 will rotate with respectto one representing e t . If ei is a vector rotating at w radians per second,then e 2 will rotate at w + 2tt',j. radians per second.Figure 3 shows the variation of the phase angle cp which the resultant,R, of ei and e 2 makes at any given instant with the vector ei. Whent = 0, the two vectors are in phase and cp = 0. At a later time 2iryl =90 degrees, so e 2 and ei are at right angles and tan cp = e 2/ei = x. When2ir[j.t = 180 degrees, cp is again zero. This process gives the variations incp shown by Figure 4 . Themaximum value of