UHF Analog Driver/Transmitter/
Chapter 5, Detailed Alignment Procedures
Translator
LX Series, Rev. 3
5-5
channel that the upconverter is on. The
channel number should be blinking.
To change the channel, hit the
+
button
to step through the channels until the
desired channel is reached.
To select a 10kHz offset to the channel
frequency, use the
>
button to move
the curser to the LO frequency listed
below the Channel number, and keep
pressing the
>
button until the desired
digit is blinking, and then use the
+
button to change the frequency.
Example:
Nominal LO frequency for Channel 14 =
0517.00 MHz. To generate a + offset,
change the LO frequency to 0517.01
MHz. To generate a – offset, change the
LO frequency to 0516.99 MHz.
5.2.7 Linearity Correction
Adjustment
As shipped, the exciter was preset to
include amplitude and phase pre-
distortion. The pre-distortion was
adjusted to approximately compensate
the corresponding non-linear distortions
of the Power Amplifier.
NOTE:
On the IF processor board inside
the module the correction enable/disable
jumper W12 on J30 must be in the
Enable position, on pins 2 & 3. This is
the normal operating position.
Set up a spectrum analyzer with
100 kHz resolution bandwidth and
100 kHz video bandwidth to monitor the
intermodulation products of the RF
output signal of the Power Amplifier.
A typical red field spectrum is shown in
Figure 5-1. There are three Linearity
Corrector stage adjustments located on
the front panel of the IF Processor
Module. The adjustments are threshold
settings that are adjusted as needed to
correct for any amplitude or phase
intermod problems. Adjust the top
linearity correction adjustment R211
threshold cut in for the in phase
amplitude distortion pre-correction that
is needed. Next adjust the middle
linearity correction adjustment R216
threshold cut in also for the in phase
amplitude distortion pre-correction that
is needed. Finally adjust the bottom
linearity correction adjustment R231
threshold cut in for the quadrature
phase distortion pre-correction that is
needed. The above pots are adjusted
for the greatest separation between the
peak visual carrier and the intermod
products.
NOTE:
These pots affect
many other video parameters, so care
should be taken when adjusting the
linearity correction.
Figure 5-1. Typical Red Field Spectrum
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Страница 99: ...APPENDIX A LX SERIES ANALOG SYSTEM SPECIFICATIONS...
Страница 102: ...APPENDIX B DRAWINGS AND PARTS LISTS...
Страница 105: ...APPENDIX C TRANSMITTER LOG SHEET...
