4-32
888-2629-200
10/6/10
WARNING: Disconnect primary power prior to servicing.
Section 4 Theory of Operation
Maxiva ULX COFDM Series
The CD2007 output amplifier board and the phase and gain board receive their power
form the power supply board mounted on the tray. This power supply produces 28 Vdc
at 4.5 amps maximum.
The phase and gain board provides a continuously variable phase change of 180
degrees, which is used to combine multiple PA cabinets. It also has an attenuator, driven
by the transmitter’s ALC (automatic level control) circuit, which has a 0 to 15 dB
variable range. The phase and gain board is used by the transmitter to control cabinet
power (by driving the PA modules with more or less input power) and cabinet phasing.
Figure 4-12 gives a block diagram of the phase and gain board.
Figure 4-12 Phase and Gain Board Block Diagram
The CD2007 output amplifier has a peak rating of 35 watts and is generally operated
over a 0.3 to 4.0 watt average range for digital, to allow adequate peak to average power
headroom. In the analog TV mode its output is up to 6 watts peak of sync with 10%
aural. At 28 Vdc supply voltage this amplifier requires approximately 5.2 amps to
produce 35 watts output. It has an efficiency of 24% at 35 watts output.
The typical gain of the predriver tray is 32 dB, and the gain of the predriver assembly
(which includes the 2-way splitter) is 28 dB.
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