Lesson 1/ Learning Event 3
(1) An input level of -26 dBm arrives on the receive line and enters
the equalizer (EQ) which introduces a 6-dB loss, resulting in an output
level of -32 dBM.
The input attenuator ahead of the line amplifier
inserts 22 dB loss, reducing the amplifier input level to -54 dBm.
Amplification of 52 dB produces -2 dBm, the required value of equal-level
patching.
(2) The input attenuator ahead of the second amplifier inserts a 21-dB
loss, reducing the amplifier input level to -23 dBm. Amplification of 35
dB gives 12 dBm level for the equipment.
(3) Every amplifier is rated in terms of its maximum undistorted output
level.
Care must be exercised in adjusting circuit gains and losses to
never exceed that output level, especially when the amplifiers carry
multi-channel (multiplexed) signals.
Overloading an amplifier causes it
to operate in a nonlinear manner; this in turn causes crosstalk between
the various multiplexed channels.
This type of impairment is called
interchannel interference.
Figure 1-6.
Energy Level Diagram of an Equal-Level
Patching Circuit.
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