Specifications

AN93
Rev. 0.9 205
Power Line Related Noise
Figure 73. Odd Harmonics of 50 Hz Manifest as Horizontal Lines Spaced at 100 Hz
Causes:
 Unbalanced Phone Line
 High AC Leakage supply
 Poor CMR in Modem
Solutions:
 Fix Phone Line.
 Ground the system to earth or Float completely via battery.
 Use analog supply with lower ac Leakage