User's Manual

Innovator CU0TD-1/CU0RD-1 – CU4TD/CU4RD System Description
ATSC Transmitter/Regenerative Translator
Instruction Manual, Rev. 2 18
Pre-Filter Sample (Non-Linear Distortion)
The pre-filter sample from the pre-filter coupler connects to (J3), the RF input 1 jack,
located on the rear panel of the driver drawer. This sample connects to the modulator
board where it is used in the correction system.
Post-Filter Sample (Linear Distortion)
The post-filter sample from the post-filter coupler connects to (J4), the RF input 2 jack,
located on the rear panel of the driver drawer. This sample connects to the modulator
board where it is used in the correction system.
IMPORTANT NOTES:
RF feedback sample lines must not be disturbed when adaptive pre-correction is
enabled. If a sample line is removed, the appropriate pre-correction mode must first be
disabled and only re-enabled after the feedback signal is re-connected. RF feedback
sample #1 is feedback for the non-linear pre-corrector system and sample #2 is used
for the linear pre-corrector system.
The adaptive pre-correction systems are likely to be significantly affected if the sense
port is moved to another coupler port with a different level or if a sample level is
changed significantly (a few dB). If the linear pre-corrector system is exposed to this
scenario it may generate a notable ripple in the output that may translate into an
increase (or decrease) of the measured RMS level. Should this situation occur, the only
way to restore proper operation is to reset the linear corrector using the controller's 'Set
To Neutral' command or the web interface's 'Reset Current Curve To Factory' command
and allow the pre-corrector system to start over again.
The On Channel RF output of the amplifier drawer either connects directly to the low
pass filter and digital mask filter and then to the antenna in single amplifier systems or
to a combiner, pre-filter coupler, low pass filter, the digital mask filter, post-filter output
coupler and finally to the antenna in multiple amplifier systems. The post-filter output
coupler provides a forward and a reflected power sample to the system metering board
which detects the samples and supplies the forward and reflected power levels to the
exciter/driver drawer for use in the metering circuits.