UHF Analog Driver/Transmitter/
Chapter 2, System Description,
Translator
Maintenance & Remote Control Connections
LX Series, Rev. 3
2-7
Table 2-12. IF Processor Front Panel Control Adjustments
POTENTIOMETERS
DESCRIPTION
FREQUENCY
RESPONSE
EQUALIZER
These three variable resistors, R103, R106 & R274, adjust the
depth of gain for the three stages of frequency response correction.
ALC GAIN
Adjusts the gain of the transmitter when the transmitter is in the
Auto ALC position.
MAN GAIN
Adjusts the gain of the transmitter when the transmitter is in the
Manual ALC position.
LINEARITY
CORRECTION
These three variable resistors adjust the threshold cut in for the
three stages of linearity pre-correction. R211 and R216, the top
two pots, are adjusted to correct for in phase amplitude distortions.
R 231, the bottom pot, is adjusted to correct for quadrature phase
distortions.
Table 2-13. IF Processor Front Panel Sample
SMA CONNECTOR
DESCRIPTION
IF SAMPLE
Sample of the pre-corrected IF output of the IF Processor
2.1.4 (A5) VHF/UHF Upconverter
Module Assembly (1303829;
Appendix B)
The VHF/UHF Upconverter Module
Assembly contains (A1) a Downconverter
Board Assembly (1303834), (A3) a First
Conversion Board, LX Series (1303838),
(A2) a L-Band PLL Board, LX Series
(1303846) and (A4) an Upconverter
Control Board (1304760).
A 0 dBm 44 MHz IF input to the
upconverter through the backplane
board is applied to a mixer mounted on
the first conversion board. Also applied
to the mixer is a nominal 1 GHz LO1.
The mixer converts it to a nominal
frequency centered at 1044 MHz. A
filter selects the appropriate conversion
product, which is then amplified to a
level of approximately –4 dBm. The
frequency of the first conversion LO1
can be shifted by ± 10 kHz to generate
channel offsets of 10kHz. For +offsets
the frequency is 999.99 MHz and for –
offsets the frequency is 1000.01 MHz.
This signal is applied to a second mixer
mounted on the downconverter board
that converts it back to a broadcast
channel (2-69) by an LO2 that operates
in 100kHz steps between 1.1-1.9 GHz
depending on the channel selected. The
LO2 frequency equals the Channel
center frequency plus the LO1 frequency
plus 44 MHz. (As an example CH14+:
Center Frequency is 473.01 MHz and
LO1 is 999.99 MHz therefore LO2 is
473.01 + 999.99 + 44, which equals
1517.00 MHz.)
The output of the mixer is applied to a
900 MHz Low pass filter to remove
unwanted conversion products. The
