Specifications

to instant, the number of RF amplifiers that are switched on also
changes.
For a positive modulation peak, which requires a high RF voltage
(and power) at the transmitter output, a large number of RF
Amplifiers are turned on. For a 100% negative modulation peak,
which corresponds to zero transmitter RF voltage (and power)
output, all the RF Amplifiers are turned off.
An important point to note is that the transmitter reaches it’s
positive peak modulation capability when all the RF Power
Amplifiers are turned on and it’s negative peak (-100%) when all
the modules are turned off.
4.2.6.4 Conclusion
The transmitter uses Digital Amplitude Modulation for superior
audio performance and highest AC to RF efficiency.
Digital Amplitude Modulation is created by a two step process.
1. Audio +DC (carrier level) is converted into digital
wordsbyanA/DConverter.
2. The digital words are used to turn on/off the 160 RF
Power Amplifiers which create amplitude variations of
the RF according to the incoming audio signal and
carrier set level.
The peak positive modulation of the transmitter occurs when all
160 RF Power Amplifiers are turned on.
The peak negative modulation (-100%) occurs when all the RF
Power Amplifiers are turned off.
WARNING
ENSURE THAT THE TRANSMITTER IS TURNED OFF AND ALL
PRIMARY POWER IS TURNED OFF AT THE WALL DISCONNECT
SWITCH BEFORE OPENING ANY DOOR OR PANEL. BEFORE
REMOVING PANELS OR OPENING DOORS, VERIFY THAT THE
RF AMP POWER SUPPLY IS DISCHARGED BY CHECKING
“PA+VDC” ON THE FRONT PANEL MULTIMETER. USE A VOLT-
METER TO VERIFY THE POWER SUPPLIES HAVE BEEN DIS-
CHARGED PRIOR TO TOUCHING ANY COMPONENTS.
4.3 Protection Of Personnel
The following is a list of protection devices installed in the
transmitter designed for the safety of maintenance personnel. It
Figure 4-4. Digital AM Modulation
12/16/03 888-2339-002 4-7
WARNING: Disconnect primary power prior to servicing.