UBS Axcera 837B-5 5000-Watt UHF Translator User Manual 315947
UBS-Axcera 5000-Watt UHF Translator 315947
Contents
Chapter 5
4-6 kW UHF Translator Chapter 5, Detailed Alignment Procedures
837B, Rev. 0 5-1
Chapter 5
Detailed Alignment Procedures
The 837B translator was aligned at the
factory and should not require any
additional alignments to achieve normal
operation.
This translator takes the On channel RF
input to the Receiver Tray and converts it
to the desired UHF On Channel RF Output
at the systems output power level.
If the (Optional) Modulator Kit is
purchased, this translator can also
operate using the baseband audio and
video inputs or, if the (Optional) 4.5-MHz
composite input kit is purchased, either a
single composite video + 4.5-MHz input
or separate baseband video and audio
inputs.
Make sure that the RF output at J2 of the
(A11) coupler is terminated into a
dummy load of 4000 to 6000 watts,
depending on your systems output
power. While performing the alignment,
refer to the test data sheet for the
translator and compare the final readings
from the factory with the readings on
each of the trays. They should be very
similar. If a reading is off by a significant
amount, the problem is likely to be in
that tray.
Switch on the main AC and the UHF
exciter circuit breakers on the AC
distribution panel behind the rear cabinet
door of the Exciter Cabinet.
5.0 UHF/VHF Receiver
Tray.)(1142479 or 1265-1100;
Appendix C)
Connect a UHF or VHF Input that is
at the desired Channel Frequency, to
J1 50Ω or J5 75Ω located on the rear
of the (A7) VHF/UHF Receiver Tray.
Check that the On/Off Switch located
on the rear of the Tray is On.
Note: If the Red LED, DS1 is lit, +12
VDC is present at the input of the
Receiver Tray and may damage any test
equipment connected to it. Remove the
fuse F1, DS1 will not be lit, before
connecting test equipment to the input
jack of the Receiver Tray.
5.0.1 (A7) UHF Filter, DC Multiplexed
{(1035-1204, 50
Ω
or 1035-1207,
75
Ω
), VHF Filter, LB, DC Multiplexed
(1035-1902, 50
Ω
or 1035-1903,
75
Ω
) or VHF Filter, HB, DC
Multiplexed (2065-1024, 50
Ω
or
2065-1023, 75
Ω
); Appendix D)}
The input UHF or VHF signal (-61 dBm to
-16 dBm) is fed to the filter which has
been factory swept for 6 MHz Bandwidth
at the Channel frequency and should not
be tuned in the field. The output of the
filter is directed to the J1 input of (A8)
the Dual Stage Amplifier Assembly.
5.0.2 (A8-A1) Dual Stage Amplifier
Board (1227-1501; Appendix D)
Mounted in: (A8) a Dual Stage Amplifier
Assembly (1227-1503).
The Dual Stage Amplifier Board has been
factory set to the channel frequency and
contains no customer tuning
adjustments. The board has
approximately +13 dB or +26 dB of gain,
depending on whether Jumper W1 on J5
is in place.
5.0.3 (A9) UHF Filter {(1007-1101),
VHF LB Filter (1034-1202) or VHF HB
Filter (2065-1000); Appendix D}
The UHF or VHF Filter has been factory
swept for 6 MHz Bandwidth at the
Channel Frequency and should not be
tuned in the field. The output of the filter
(-50 dBm to -5 dBm) is fed either
through the additional amplifier stage on
the Variable Gain Amplifier Board or to
4-6 kW UHF Translator Chapter 5, Detailed Alignment Procedures
837B, Rev. 0 5-2
(A10-A1) the Downconverter/Filter
Board.
5.0.4 (A4) Channel Oscillator
Assembly, Dual Oven (1145-1202;
Appendix D)
Contains: The Channel Oscillator Board,
Dual Oven (1145-1201).
1. Connect the main output of the
Channel Oscillator (J1) to a
spectrum analyzer, adjusted to
view the crystal frequency.
Peak the tuning capacitors C6 and
C18 for maximum output. Then
tune L2 and L4 for maximum
output. The output level should
be approximately +5 dBm and the
Oven Temperature should be
maintained at 50°C.
If a spectrum analyzer is not
available, connect a DVM to TP1
on the x8, x4 or x2 Multiplier
Board. Tune capacitors C6 and
C18 for maximum voltage at TP1.
Then tune L2 and L4 for maximum
voltage at TP1.
2. Connect the sample output of the
Channel Oscillator at J2 to a
suitable counter and tune C11,
Coarse Adjust, and C9, Fine
Adjust, to the crystal frequency.
Do not re-peak C6, C18, L2 or L4
because this may change the
output frequency.
Note: While adjusting C9 and C11 to the
crystal frequency the peak voltage
monitored at TP1 of the Multiplier
Board should not decrease. If a
decrease does occur a problem
with the crystal is likely.
3. Reconnect the main output at J1
of the Channel Oscillator to the
Input Jack J1 of the Multiplier
Board.
Note: If the Optional Frequency
Correction Kit is purchased a VCXO
Assembly (1145-1206), containing
a VCXO Board (1145-1204), will be
used instead of the standard
Channel Oscillator Board. The
adjustment will be the same as
above except that the frequency is
adjusted by moving the Jumper
W1 on Jack J6, located on the IF
PLL Board (1109-1002), to Pins 2
& 3, Fixed Bias, and adjusting R15
on the IF PLL Board for -3 VDC at
FL2 of the VCXO Assembly. Move
the Jumper W1 on Jack J6 to
between Pins 1 & 2, AFC. Connect
the Oscillator Sample output, at
(J2) of the Channel Oscillator or
the Front Panel Sample Jack (J9),
to a suitable Frequency Counter
and tune C11, Coarse Adjust, to
the desired frequency. Do not
re-peak C6, C18, L2 or L4 because
it may change the output
frequency.
Reconnect the main output (J1) of
the Channel Oscillator (+5 dBm) to
the input (J1) of the Multiplier
Board. DS1 the Red Unlock
Indicator, located on the IF PLL
Board, should not be lit.
5.0.5 (A5-A1) x8 Multiplier Board
{(1227-1002), x4 Multiplier Board
(1227-1525) or x2 Multiplier Board
(1227-1524); Appendix D}
Mounted in (A5) a Multiplier Enclosure
(1265-1125).
During Normal operation, the Green LED
DS1, which can be seen through the
access hole in the Enclosure Assembly,
will be lit to indicate that the L.O. is
present at the output of the x8 Multiplier
Board.
1. Connect a Spectrum Analyzer to
the Output Jack (J2) of the board.
2. Tune C4, C6, C10, C12, C18 and
C20 on the x8 and the appropriate
caps on the other boards for
maximum output. Readjust all the
4-6 kW UHF Translator Chapter 5, Detailed Alignment Procedures
837B, Rev. 0 5-3
Capacitors to minimize the
seventh and the ninth harmonics,
they should be at least -30 dB
down, without affecting the x8
Multiplier Output.
If a Spectrum Analyzer is not available a
DC voltmeter can be used as follows but
the harmonic frequencies must be
minimized to prevent interference with
other Channels.
1. While Monitoring each Test Point
with a DC voltmeter, maximize the
voltage by tuning the Broadband
Multipliers in the following
sequence.
2. For x8 Multiplier Board: Monitor
TP1 with a DVM and tune C4 for
maximum. (Typical .6 VDC)
Monitor TP2 and tune C6 and C10
for maximum. (Typical 1.2 VDC)
Monitor TP3 and tune C12 and C18
for maximum. (Typical 2 VDC)
Monitor TP4 and tune C20 for
maximum.
Re-peak C12 and C10 while
monitoring TP4. (Typical 3.5 VDC)
For x4 Multiplier: Monitor TP1 with
a DVM and tune C4 for maximum.
(Typical .6 VDC)
Monitor TP2 and tune C6 and C10
for maximum. (Typical 1.2 VDC)
Monitor TP3 and tune C12 for
maximum.
Re-peak C12 and C10 while
monitoring TP3. (Typical 2 VDC)
For x2 Multiplier: Monitor TP1 with
a DVM and tune C4 for maximum.
(Typical .6 VDC)
Monitor TP2 and tune C6 for
maximum.
Re-peak C4 and C6 while
monitoring TP2. (Typical 1.2 VDC)
The Green LED DS1 should be lit which
indicates that the L.O. is present at the
Output Jack J2 of the Multiplier Board.
The output of the Multiplier at J2 is
connected to (A6) a UHF or VHF Filter.
5.0.6 (A6) UHF Filter {(1007-1101),
VHF LB Filter (1034-1211) or VHF HB
Filter (2065-1000); Appendix D}
This filter has been factory swept at the
L.O. frequency and should not be tuned
without proper equipment. The output of
the filter (+15 dBm) is connected to J2
on (A10) the Downconverter/Filter
Assembly.
5.0.7 (A10-A1) Downconverter/
Amplifier Board (1227-1502;
Appendix D)
Mounted in: The (A10)
Downconverter/Amplifier Assembly
(1227-1505).
The Mixer contains no adjustments and
has a L.O. input of approximately +12
dBm in level applied to J2 and a -47 dBm
to -2 dBm RF input applied to J1. The
output IF level at J3 will be -55 dBm to
-10 dBm.
1. Connect a Spectrum Analyzer to
the Output Jack J3 and adjust L1,
C2 and L3 for best frequency
response.
2. Adjust C8 and R3 to notch out the
Aural IF Frequency.
The IF output at J3 (-55 dBm to -10
dBm) is fed to the IF Filter/ALC Board. If
needed a 10 dB Pad can be added to the
circuit by moving the jumpers on J4 and
J5 to the In position.
5.0.8 (A11-A1) IF Filter/ALC Board
(1227-1504; Appendix D)
Mounted in: The (A11) IF Filter/ALC
Enclosure (1265-1105).
1. Check that Switch S1, located on
the IF Filter/ALC Board, is in the
Auto ALC and that the output of
the Board at J2 is approximately 0
dBm Output, adjust R23 if needed.
4-6 kW UHF Translator Chapter 5, Detailed Alignment Procedures
837B, Rev. 0 5-4
5.0.9 (A11-A2) (Optional) SAW
Filter/Amplifier Board (1035-1211;
Appendix D)
Mounted in: The (A11) IF Filter/ALC
Enclosure (1265-1105).
This board is used for additional adjacent
Channel rejection only if needed and may
not be part of the Tray.
The board contains no tuning
adjustments. The Jumpers W1 and W2
on J4 and J5 are placed for Attenuator In
or Attenuator Out as needed to give the
same output level at J2 as was at J1.
5.0.10 (A2) ±12V Power Supply
Board (1092-1206; Appendix D)
This board contains no adjustments.
Note: If the (Optional) Frequency
Corrector Kit is part of the tray, perform
the following adjustments. If the
Frequency Corrector Kit is not part of the
tray, the tray is aligned and ready for
normal operation.
5.0.11 (A15) (Optional) IF Carrier
Oscillator Board (1100-1206;
Appendix D)
1. Monitor J3 with a Spectrum
Analyzer and observe the 38.9
MHz Visual IF signal at +5 dBm.
2. Connect a Frequency Counter to J2
on the board or to J9 on the Front
Panel and adjust C17 for 38.9
MHz.
3. Connect a Frequency Counter to J1
and check for the 50 kHz signal.
Adjust C17, if needed, to attain
the 50 kHz frequency. Remove
the Jack on J5. DS2 the Unlock
Indicator should light. Replace the
Jack onto J5.
5.0.12 (A13) (Optional) IF Filter/
Limiter Board (1109-1001; Appendix
D)
1. Monitor the Aural Notch Test
Output of the board at J5 and
move the Jumper W1 on Jack J4 to
between Pins 2 & 3, Test Position.
Adjust C17 to the Aural IF
Frequency, then adjust R10 to
eliminate or minimize the Aural IF
signal. Move the Jumper W1 on
Jack J4 back to between Pins 1 &
2, Operate Position.
2. Monitor the IF CW Output of the
board at J6 with an Oscilloscope
and adjust R12 and C21 for
maximum Video Signal or connect
a Spectrum Analyzer, in Zero
Span, to J6 and adjust R12 and
C21 for Minimum Video Signal
amplitude ripple on the displayed
signal.
3. Adjust R15 for +3 dBm or
Maximum output level if +3 dBm
cannot be attained.
5.0.13 (A14) (Optional) IF PLL Board
(1109-1002; Appendix D)
Check that the Red LED DS1, Unlock
Indicator, located on the board is not lit.
If DS1 is lit, follow the alignment
procedure for setting up the VCXO
Channel Oscillator using R9 on the IF PLL
Board to set up the AFC Voltage for the
Frequency of the VCXO. If it is still lit,
check the 50 kHz reference output of the
(A15) IF Carrier Oven Oscillator. If
needed, follow the alignment procedure
for the IF Carrier Oven Oscillator Board.
5.0.14 (A16) (Optional) IF Amplifier
Board, High Gain (1197-1126;
Appendix D)
This board contains no customer
adjustments. The amplified IF output
from the IF Filter/ALC Board connects to
the IF Filter Limiter Board.
4-6 kW UHF Translator Chapter 5, Detailed Alignment Procedures
837B, Rev. 0 5-5
The Receiver Tray is now set up and
ready for normal operation.
5.1 UHF Exciter Tray with Baseband
Video and Audio Inputs (Must have
Optional Modulator Kit.)(1142458 or
1245-1100; Appendix C)
This tray has adjustments for video
levels, audio modulation levels, and other
related parameters.
Connect an NTSC baseband video test
signal input (1 Vpk-pk) to the translator
video input jacks J2 or J1 on the rear of
the tray. Jacks J1 and J2 are loop-
through connected; the unused jack can
be used as a video source for another
transmitter by removing jumper W4 on
jack J3 on (A5) the sync tip clamp/
modulator board (1265-1302). Connect a
baseband audio input (+10 dBm) to the
balanced audio input terminal block TB1-
1 [+], TB1-2 [-], and TB1-3 [ground] or,
if stereo/composite audio is provided,
connect it to BNC jack J3 or J13, the
composite audio input jack. Jacks J3 and
J13 are loop-through connected; the
unused jack can be used as an audio
source for another transmitter by
removing jumper W1 on jack J15 on the
aural IF synthesizer.
Select the baseband input operation by
applying a baseband select, using a
jumper or closed contacts, connected
between J7-6 and J7-7 on the rear of the
tray. Look at the front panel meter on
the UHF exciter tray. In the video
position, the meter indicates active video
from 0 to 1 Vpk-pk. The normal video
input level is 1 Vpk-pk on the meter. If
this reading is not at the proper level, the
overall video level can be changed by
adjusting video level control R12 on (A5)
the sync tip clamp/modulator board
(1265-1302).
Switch the meter to the audio position
that indicates the audio deviation
(modulation level) of the signal from 0 to
100 kHz. The aural IF synthesizer board
was factory set for a ±25-kHz deviation
with a balanced audio input of +10 dBm.
If the reading is not at the correct level,
adjust balanced audio gain pot R13 on
the aural IF synthesizer board, as
necessary, to attain the ±25-kHz
deviation. The aural IF synthesizer board
was factory set for a ±75-kHz deviation
with a composite audio input of 1 Vpk-
pk. If this reading is not correct, adjust
composite audio gain pot R17 on the
aural IF synthesizer board, as necessary,
for the ±75-kHz deviation.
5.2 UHF Exciter Tray with (Optional)
4.5-MHz Composite Input Kit
With the (Optional) 4.5-MHz composite
input kit, the UHF exciter can operate
using either the separate video and audio
baseband inputs or the single 4.5-MHz
composite input. The 4.5-MHz composite
input kit includes a composite (A24) 4.5-
MHz filter board and (A25) a 4.5-MHz
bandpass filter board.
To operate the transmitter using the 4.5-
MHz composite input, remove the
baseband select command from J7-6 and
J7-7 on the rear of the tray.
Connect a multiburst test signal from an
envelope delay measurement, set to the
input of the tray, at J1 or J2. On (A24)
the composite 4.5-MHz filter board,
connect an oscilloscope between J7, the
center pin, and pin 1 or 3, which are
ground. If necessary, adjust C21 for the
best frequency response. Adjust R32 for
a signal level of 1 Vpk-pk on the
oscilloscope. The output, as measured at
J6 and J7 of the board, should be video
only, with a minimum 4.5-MHz aural
subcarrier.
On (A25) the 4.5-MHz bandpass filter
board, adjust the filter with L2, C3, L4,
and C7 for a frequency response of no
greater than ±.3 dB from 4.4 to 4.6 MHz.
Adjust C19 for an overall peak-to-peak
variation of less than ±.3 dB from 4.4
MHz to 4.6 MHz. Recheck the frequency
4-6 kW UHF Translator Chapter 5, Detailed Alignment Procedures
837B, Rev. 0 5-6
response; it may have changed with the
adjustment to the envelope delay.
5.3 UHF Exciter Tray with Receiver
Tray, or either (Optional) Baseband
or (Optional) 4.5-MHz Composite
Input
The IF section of the UHF exciter tray
includes adjustments for automatic level
control (ALC), linearity (amplitude
predistortion), and phase (phase change
vs. level) predistortion for correction of
the nonlinearities of the RF amplifier
trays. The upconverter section also
includes adjustments to the local
oscillator chain tuning and the local
oscillator center frequency tuning. Both
of these were completed at the factory
and should not need to be adjusted at
this time.
Move the Operate/Standby switch on the
UHF exciter tray to Standby. The setup of
the RF output includes adjustments to
the drive level for the UHF amplifier
trays, the adjustment of the linearity and
phase predistortion that compensate for
any nonlinear response of the amplifier
trays, and the gain and phasing
adjustments of the UHF amplifier trays.
Verify that all red LEDs on the ALC board
are extinguished. The following list
describes the meaning of each LED when
it is illuminated:
• DS1 (Input Fault) – Indicates that an
abnormally low or no IF is present at
the input of the board
• DS2 (ALC Fault) – Indicates that the
ALC circuit is unable to maintain the
signal level requested by the ALC
reference. Normally, this is due to
excessive attenuation in the linearity
signal path or the IF phase corrector
signal path or because jumper W3 on
J6 is in the Manual ALC gain position.
• DS3 (Video Loss) – Indicates a loss of
video at the input of the board
• DS4 (Mute) – Indicates that a visual
Mute command is present (not used
in this configuration)
• DS5 (Modulator Enable) – Indicates
that the modulator IF output is
selected. This LED is only used if a
receiver tray is present in the system.
DS5 is always on when there is no
receiver.
The ALC is muted when the translator is
in Standby. To monitor the ALC, check
that the on/off circuit breakers on the AC
input assembly in the rear of the
Amplifier Array Cabinets are Off and
switch the translator to Operate. Adjust
the power adjust gain pot on the front
panel of the UHF exciter tray to obtain
+0.8 VDC on the front panel meter in the
ALC position. On (A8) the ALC board,
move jumper W3 on J6 to the Manual
position, between pins 2 and 3, and
adjust R87 on the ALC board for +0.8
VDC on the front panel meter in the ALC
position. Move jumper W3 back to Auto,
between pins 1 and 2; this is the normal
operating position. The detected IF signal
level at J19-2 on the ALC board is
connected to the transmitter control
board that distributes the level to the
UHF amplifier trays. The level is used as
a reference for the automatic gain control
(AGC) in each amplifier tray.
5.3.1 (A6) (Optional) Delay Equalizer
Board (1227-1204; Appendix D)
This board has been factory tuned and
should not be retuned without the proper
equipment. If it is necessary to tune the
board:
1. Select a sinX/X test signal as the
video source to the delay equalizer
board.
2. Monitor the video output of the
board at video sample jack J2 with
a video measuring set (VM700) that
has been adjusted to measure
group delay.
4-6 kW UHF Translator Chapter 5, Detailed Alignment Procedures
837B, Rev. 0 5-7
3. Tune the four stages of the board
using the variable inductors (L1-L4)
and potentiometers (R7, R12, R17,
and R22) until the signal attains the
FCC group delay curve. The stages
are arranged in order of increasing
frequency. Adjust R29 as needed to
attain the same level coming out of
the board as is going into the
board.
5.3.2 (A24) (Optional) Composite
4.5-MHz Filter Board (1227-1244;
Appendix D)
The (A24) (optional) composite 4.5-MHz
filter board will only function properly
with a 4.5-MHz composite input signal
and with the 4.5-MHz composite input
selected.
Connect the test signal from an envelope
delay measurement set to the video
input of the tray at J1 or J2.
Connect an oscilloscope to jack J7, video
out, between the J7 center pin and pin 1
or 3 ground. Adjust C21, frequency
response, if needed, for the best
frequency response. Adjust R32, video
gain, for a signal level of 1 Vpk-pk on the
oscilloscope.
The output at J6 and J7 of the board
should be video only with no 4.5-MHz
aural subcarrier.
5.3.3 (A25) (Optional) 4.5-MHz
Bandpass Filter Board (1265-1307;
Appendix D)
The (A25) (optional) 4.5-MHz bandpass
filter board will only function properly
with a 4.5-MHz composite input signal
and with the 4.5-MHz composite input
selected.
Adjust the filter with L2, C3, L4, and C7
for a frequency response of no greater
than ±.3 dB from 4.4 to 4.6 MHz.
Adjust C19 for an overall peak-to-peak
variation of less than ±.3 dB from 4.4
MHz to 4.6 MHz.
Recheck the frequency response; it may
have changed with the adjustment of the
envelope delay. If necessary, retune the
board.
5.3.4 (A7) (Optional) IF Carrier
Oscillator Board (1191-1404;
Appendix D)
To align (A7) the IF carrier oscillator
board:
1. While monitoring J3 with a
spectrum analyzer, observe the
45.75-MHz visual IF (typical +5
dBm).
2. Connect a frequency counter to J3
and adjust C17 for 45.750000 MHz.
3. Connect a frequency counter to J1
and check for 50 kHz; this is the
aural phase lock loop (PLL)
reference.
5.3.5 (A5) (Optional) Sync Tip
Clamp/ Modulator Board (1265-
1302; Appendix D)
To align (A5) the sync tip clamp/
modulator board:
1. Determine if jumper W4 on jack J3
is present. Jumper W4 terminates
the video input into 75Ω. Remove
jumper W4 if the video loop-
through is required on the rear
chassis at jacks J1 and J2.
2. Set the controls R20, the white clip,
R24, the sync clip, and R45, the
sync stretch cut-in, to their fully
counter-clockwise (CCW) position.
Set R48, the sync magnitude, fully
clockwise (CW).
3. Place the jumper W7 on jack J4 to
the clamp off, disable, position.
4-6 kW UHF Translator Chapter 5, Detailed Alignment Procedures
837B, Rev. 0 5-8
4. Connect a 5-step staircase video
test signal to the input of the
transmitter.
5. Monitor TP2 with an oscilloscope.
Adjust R12, the video gain pot, for
1 Vpk-pk.
6. Change the video input test signal
to a multiburst test pattern. While
monitoring TP2, adjust C8 and R32
for a flat-frequency response.
Change the input video test signal
back to the 5-step staircase.
7. Monitor TP2 with an oscilloscope.
Adjust the pot R41, manual offset,
for a blanking level of -0.8 VDC.
The waveform in Figure 5-1 should
be observed at this point. Move
jumper W2 on J4 to the clamp
enable position. Adjust pot R152,
depth of modulation, for a blanking
level of -0.8 VDC.
0
V
o
lt
s
.1 Volts
Figure 5-1. Waveform at TP2.
Note: The waveform in Figure 5-1 represents the theoretical level for proper
modulation depth. Step 8 below describes how to set the modulation depth
through the use of a television demodulator or a zero-spanned spectrum
analyzer tuned to the visual IF frequency.
8. The following test setup is for the
adjustment of the depth of modulation
and ICPM at IF:
A. Remove the cable that is now
on J18. Connect the double
sideband 45.75-MHz visual IF
signal from J18 to a 10-dB
splitter/coupler. Connect the
coupled port of the splitter/
coupler to the RF input of a
television demodulator.
Connect the direct port to a
spectrum analyzer.
B. Connect the 75-Ω video output
of the demodulator to the video
input of a waveform monitor.
For incidental carrier phase
modulation (ICPM)
measurements, also connect
the quadrature output of the
demodulator to the horizontal
input of the waveform monitor
using a 250-kHz low-pass filter.
(An oscilloscope can be used in
place of a waveform monitor).
C. Set the controls of the
demodulator as follows:
• Detector Mode: Cont
• Sound Trap: In
• Zero Carrier: On
• Auto: Sync
• Audio Source: Split
• De-Emphasis: In
9. Move jumper W7 on J4 to the clamp
disable position. Readjust pot R41,
4-6 kW UHF Translator Chapter 5, Detailed Alignment Procedures
837B, Rev. 0 5-9
manual offset, for the correct depth
of modulation by observing the
demodulated waveform on the
waveform monitor or on the
spectrum analyzer set to zero span.
10. Check the demodulated video for
the proper sync-to-video ratio (sync
is 28.6% of the total white video
signal). If sync stretch is needed,
adjust R45, sync stretch cut-in,
until sync stretch occurs. Adjust
R48, sync stretch magnitude, for
the proper amount of stretch.
Readjust R41, manual offset, if
necessary, for the correct depth of
modulation.
11. Move jumper W7 on J4 to the clamp
enable position. Readjust pot R152,
the depth of modulation, for the
correct depth of modulation.
12. Set the waveform monitor to
display ICPM. Preset R53 fully CCW,
adjust C78 for the greatest effect at
white on the ICPM display, and
adjust R53 for minimum ICPM.
13. Recheck the depth of modulation
and, if necessary, adjust R152,
depth of modulation.
14. Adjust pot R70 for a level of
approximately -10 dBm on the
spectrum analyzer at J18.
15. Remove the video input. Place the
front panel meter in the video
position and, while monitoring the
meter, adjust pot R144, zero
adjust, for a reading of zero.
16. Replace the video input test
signal (the 5-step staircase).
Turn the front panel meter to
the Video position and adjust
R20 on the transmitter control
board for a reading of 100 (10
on the 0-to-10 scale). This
board does not have sync
metering.
17. Reconnect the plug to J18 and
move the spectrum analyzer test
cable to 41.25 IF output jack J16.
Tune C59 and L17-L20 to maximize
the 41.25-MHz aural IF signal and
minimize the out-of-band products.
Adjust pot R97 for -20 dBm at J16.
18. Reconnect the plug to J16 and
move the spectrum analyzer test
cable to IF output jack J20. Preset
R62, the visual IF gain pot, to the
middle. Insert a multiburst test
signal into the translator and
observe the visual frequency
response with the spectrum
analyzer set at 1 dB/division. Tune
R63 and C30, the IF frequency
response adjustments, for a flat-
frequency response (±0.5 dB).
19. While still monitoring J20 with a
spectrum analyzer, readjust R62,
visual IF gain, for a visual output
level of 0 dBm. Adjust R85, A/V
ratio, for a -10 dB aural-to-visual
ratio or to the needed A/V ratio.
Reconnect the plug to J20.
20. Using an input video test signal (the
5-step staircase) with a 100 IRE
white level, monitor TP2 with an
oscilloscope. Set the control R24,
the sync clip, just below the point
where sync clipping begins to occur.
Also, set R20, the white clip, to the
point just below where the white
video begins to clip.
Note: This procedure should be
performed after the system setup or
if linearity problems occur.
5.3.6 (A4) (Optional) Aural IF
Synthesizer Board, 4.5 MHz (1265-
1303, Appendix D)
1. The test equipment setup for (A4)
the aural IF synthesizer board, 4.5
MHz, is as follows:
A. Connect a 600-Ω balanced
audio output from an audio
oscillator to the balanced audio
4-6 kW UHF Translator Chapter 5, Detailed Alignment Procedures
837B, Rev. 0 5-10
input terminals of the tray at
TB1-1 (+), TB1-2 (-), and TB1-
3 (ground) on the rear chassis.
B. Connect the combined IF
output at J21, the IF sample on
the clamp modulator board, to
the input of an IF splitter.
Connect one output of the
splitter to the video
demodulator and the other
output to the spectrum
analyzer.
C. Connect a short cable at the
front of the demodulator from
the RF-out jack to the IF-in
jack.
D. Connect a cable from the 600-
Ω audio output jack of the
demodulator to the input of an
audio distortion analyzer.
2. Set the output frequency of the
audio oscillator to 400 Hz and the
output level to +10 dBm.
3. Center the aural carrier on the
spectrum analyzer with the
spectrum analyzer set to the
following:
• Frequency/Division: 10 kHz
• Resolution Bandwidth: 3 kHz
• Time/Division: 50 msec
• Trigger: Free run
A. Adjust L5 for approximately
+3.5 VDC at TP2.
B. The green LED DS1 should be
illuminated, indicating a locked
condition. If not, retune L5 for
a locked condition.
4. Adjust R13, balanced audio gain, on
the aural IF synthesizer board for
±25 kHz deviation.
5. Check the distortion on the aural
distortion analyzer (< 0.5%).
6. Disconnect the 600-Ω balanced
audio input to the tray. Connect a
75-Ω stereo audio input (400 Hz at
1 Vpk-pk) to composite audio input
jack J3 on the rear of the tray.
Follow the procedure in the stereo
generator instruction manual for
matching the level of the generator
to the exciter. R17 is used to adjust
the composite audio gain.
7. Check the distortion level on the
distortion analyzer (< 0.5%).
5.3.7 (A8) ALC Board (1265-1305;
Appendix D) (Part 1 of 2)
The following details the meaning of each
LED of (A8) the ALC board when it is
illuminated:
• DS1 - Red LED: Indicates that an
abnormally low IF signal level is
present at IF input connector J1
• DS2 - Red LED: Indicates that the
ALC circuit is unable to maintain the
signal level requested by the ALC
reference; this is usually due to
excessive attenuation in the linearity
or the IF phase corrector signal path,
or because the jumper W3 on J6 is in
manual gain
• DS3 - Red LED: Indicates a video loss
fault
• DS4 - Red LED: Indicates that a Mute
command is present (not used in this
configuration)
• DS5 - Green LED: Indicates that the
output from the modulator is selected
as the input to the ALC board
1. To align the ALC board, preset the
following controls in the UHF exciter
tray:
• ALC board – Move jumper W1 on J4
to disable, between pins 2 and 3 (to
disable linearity correctors); move
jumper W3 on J6 to manual, between
pins 2 and 3 (for manual gain
4-6 kW UHF Translator Chapter 5, Detailed Alignment Procedures
837B, Rev. 0 5-11
control); adjust R87, the manual gain
pot, to mid-range.
• IF phase corrector board – Move
jumper W2 on J9 to the phase
correction enable position; move the
jumper W3 on J10 to the amplitude
correction disable position.
2. The combined IF output of the sync
tip clamp modulator board is cabled
to jack J32 of the ALC board.
Remove J32 from the board and
check to see that DS1, Input Fault,
is illuminated. Reconnect J32 and
check to see that DS1 is
extinguished.
3. Jumper W3 on J6 should be in the
manual position; monitor jack J3
with a spectrum analyzer.
4. With a multiburst video signal
present, tune C4 for a flat-
frequency response of ±0.5 dB.
5. Before proceeding with part 2 of the
ALC board alignment (described in
section 5.1.10), check the IF phase
corrector board to make sure that it
is functioning properly.
5.3.8 (A9) IF Phase Corrector Board
(1227-1250; Appendix D)
Refer to the system alignment
procedures at the end of this chapter for
the set up of (A9) the IF phase corrector
board in the exciter tray. The signal level
into the board should be approximately
the same as the output of the board.
The IF input jack of the IF phase
corrector board is fed from J3, the IF
output jack of (A8) the ALC board.
The IF output jack of the IF phase
corrector board is fed to J7, the IF input
jack of (A8) the ALC board.
5.3.9 (A8) ALC Board, NTSC (1265-
1305; Appendix D) (Part 2 of 2)
Input a multiburst video test signal at the
baseband video input. Connect a
spectrum analyzer to J11. Tune C63 for a
flat-frequency response of ±0.5 dB.
Move the Operate/Standby switch on the
front panel of the translator to the
Operate position.
Place jumper W3 on jack J6 in the
Manual mode and adjust R87 for 0.8
volts at TP4.
Place jumper W3 on J6 in the Auto mode
and adjust the front panel power adjust
control A20 fully CW. If the optional
remote power raise/lower kit is present,
adjust switch S1 on the board to
maximum voltage at TP4. Adjust R74,
the range adjust, for 1 volt at TP4.
Adjust the front panel power adjust
control (A20) for 0.8 VDC at TP4. If the
optional remote power raise/lower kit is
present, adjust switch S1 on the board to
the mid-range of its travel and then
adjust the front panel Power Adjust
control (A20) for 0.8 VDC at TP4.
Disconnect the plug that is now on J12
(IF output) and monitor the output with a
spectrum analyzer. The output should be
approximately 0 dBm. Adjust R99, if
necessary, to increase the output level. If
a smaller output level is needed, move
the jumpers J27 and J28 to pins 2 and 3
and adjust R99 as needed. Reconnect
J12.
Move W2 on J5 to the cutback enable
position. Remove the input video signal
and verify that the output of the
translator drops to 25%. Adjust R71, the
cutback level, if necessary. Restore the
video input signal.
Note: This step affects the response
of the entire translator. Connect a
video sweep signal to the input of
the tray. Monitor the output of the
system with a spectrum analyzer.
Adjust C71 with R103 and C72 with
R106, as needed, to flatten the
response. C71 and C72 can be
4-6 kW UHF Translator Chapter 5, Detailed Alignment Procedures
837B, Rev. 0 5-12
adjusted for the frequency of the
correction notch being applied to the
visual response of the translator.
R103 and R106 are used to adjust
the depth and width of the correction
notch.
Controls R13, R18, and R23, the
magnitude controls, should be set fully
CW. Controls R34, R37, and R40 are the
linearity cut-in adjustments.
5.3.10 (A11) UHF Upconverter Board
(1265-1310; Appendix D)
To align (A11) the UHF upconverter
board, place W1 on J10 in the Manual
position. R10 is a gain control that is
adjusted to give a maximum output of
approximately +17 dBm at J5 of the
board with an input of 0 dBm of IF.
5.3.11 (A14-A1) Channel Oscillator
Board (1145-1201; Appendix D)
The (A14-A1) channel oscillator board is
mounted in (A14) the channel oscillator
assembly. To align this board:
1. Connect J1, the main output of the
channel oscillator, to a spectrum
analyzer tuned to the crystal
frequency. Peak the tuning
capacitors C6 and C18 for
maximum output. Tune L2 and L4
for maximum output. The output
level should be about +5 dBm. The
channel oscillator should maintain
an oven temperature of 50° C.
If a spectrum analyzer is not
available, connect a digital
voltmeter (DVM) to TP1 on the x8
multiplier board. Tune capacitors C6
and C18 for maximum voltage and
tune L2 and L4 for maximum
voltage output at TP1.
2. Connect J2, the sample output of
the channel oscillator, to a suitable
counter and tune C11, coarse
adjust, to the crystal frequency.
Tune C9 for the fine-frequency
adjustment.
Caution: Do not repeak C6, C18, L2,
or L4. This can change the output
level.
Note: While adjusting C9 and C11 to
the crystal frequency, the peak
voltage monitored at TP1 of the x8
multiplier board should not decrease.
If a decrease does occur, there may
be a problem with the crystal.
Contact the Axcera Field Service
Department for further instructions.
Note: If the VCXO oscillator in the
channel oscillator assembly is used,
the C9 fine-frequency adjust is not
on the channel oscillator board. It
can be found on the FSK w/EEPROM
board by using R9.
3. Reconnect J1, the main output of
the channel oscillator, to J1, the
input of the x8 multiplier.
5.3.12 (A15-A1) x8 Multiplier Board
(1227-1002; Appendix D)
The (A15-A1) x8 multiplier board is
mounted in an x8 multiplier enclosure
assembly. During normal operation, the
green LED DS1, which can be seen
through the access hole in the enclosure
assembly, will be lit to indicate that the
LO is present at the output of the x8
multiplier board.
Connect a spectrum analyzer to output
jack J2 of the board.
Tune C4, C6, C10, C12, C18, and C20 for
maximum output.
Readjust all of the capacitors to minimize
the seventh and the ninth harmonics of
the channel oscillator frequency. They
should be at least -30 dB down without
affecting the x8 multiplier output.
If a spectrum analyzer is not available, a
DC voltmeter can be used. When a
voltmeter is used, the harmonic
4-6 kW UHF Translator Chapter 5, Detailed Alignment Procedures
837B, Rev. 0 5-13
frequencies must be minimized to
prevent interference with other channels.
While monitoring each test point with a
DC voltmeter, maximize each test point
by tuning the broadband multipliers in
the following sequence:
• Monitor TP1 with a DVM and tune C4
for maximum (typical 0.6 VDC).
• Monitor TP2 and tune C6 and C10 for
maximum (typical 1.2 VDC).
• Monitor TP3 and tune C12 and C18
for maximum (typical 2.0 VDC).
• Monitor TP4 and tune C20 for
maximum.
• Repeak C12 and C10 while
monitoring TP4 (typical 3.5 VDC).
• The typical output level is +15 dBm.
5.3.13 (A3) +12 VDC (4A)/-12 VDC
(1A) Power Supply Board (1265-
1312; Appendix D)
There are no adjustments that need to
be made to (A3) the +12 VDC (4A)/-12
VDC (1A) power supply board. DS1 will
be lit if a +12 VDC output is connected to
J6. DS2 will be lit if a +12 VDC output is
connected to J3. DS3 will be lit if a +12
VDC output is connected to J4. DS4 will
be lit if a +12 VDC output is connected to
J5. DS5 will be lit if a -12 VDC output is
connected to J7 and J8.
5.3.14 (A17) Transmitter Control
Board (1245-1101; Appendix D)
To align the video metering, insert a
composite or some other 100-IRE test
signal into the exciter tray. Adjust R20
for a full-scale reading (1 volt) on the
bottom scale of the front panel meter of
the exciter tray in the video metering
position.
To align the audio metering, adjust the
audio input level for a ±25 kHz deviation
using a spectrum analyzer. Adjust R19 on
the board for a 25-kHz reading on the
bottom scale of the front panel meter of
the exciter tray.
This completes the detailed alignment
procedures for the UHF exciter tray.
5.4 (A1, A2, A3 & A4 and A5(5kW) &
A6(6kW) UHF Amplifier Trays,
LDMOS (1301560, low
band/1301561, mid band/1301562,
high band; Appendix C)
The UHF amplifier trays have been
adjusted at the factory to meet all
specifications, including phase
adjustment, to match the multiple trays
in an amplifier array when they are
combined. The trays should not need to
be adjusted to attain normal operation.
Any adjustments to the boards in the
trays should be performed in the Manual
Gain position, with S1 on (A8) the
amplifier control board (1265-1414) in
Manual. The idling current for the
amplifier boards are adjusted with no RF
drive applied. S1 should be in the Auto
AGC position for the normal operation of
the translator.
Connect a dummy load with a rating of a
least 600 watts to J2, the “N” connector
RF output jack of the tray being tested.
5.4.1 (A2-A1) Variable Gain/Phase
Board (1301549; Appendix D)
The board is mounted in (A2) the
variable gain/phase enclosure. There are
no adjustments to this board; it has an
AGC adjustable gain of 0 to 20 dB.
Typically with an input of +3 dBm output
is set at +19 dBm.
5.4.2 (A3-A1) 1-Watt UHF Amplifier
Board (1301547; Appendix D)
The board is mounted in (A3) the 1-watt
UHF amplifier enclosure. There are no
adjustments to this board; it has
approximately 10 dB of gain.
4-6 kW UHF Translator Chapter 5, Detailed Alignment Procedures
837B, Rev. 0 5-14
5.4.3 (A1) UHF Filter (1007-1101;
Appendix D)
Apply a multiburst test signal to the
translator. Monitor J2 with a spectrum
analyzer and tune C1 and C3 for peak
output with a flat-frequency response.
There is approximately 1 dB loss through
the filter.
5.4.4 (A4-A1) 40-Watt Amplifier
Module, (51-5379-308-00;
Appendix D)
The module is part of the 40 Watt UHF
amplifier assembly (1206693).
Gain adjustment (for the complete
amplifier), as well as quiescent current
setting by means of potentiometers
R807 and R808, is factory implemented
and should not be altered.
5.4.5 (A4-A2) Coupler Board
Assembly (1227-1316; Appendix D)
There are no adjustments to this board.
5.4.6 (A4-A3) LDMOS Amplifier
Module, (51-5379-309-00;
Appendix D)
The module is part of the LDMOS
amplifier assembly (1301556).
The working point setting is factory
implemented by means of
potentiometers R9, R11 and R12 and
should not be altered.
5.4.7 (A5-A1) 4-Way Splitter
Assembly (1301580; Appendix D)
There are no adjustments to this
assembly.
5.4.8 (A5-A2, A5-A3, A5-A4 & A5-
A5) LDMOS Amplifier Modules,
(51-5379-309-00;Appendix D)
Each module is part of a LDMOS
amplifier assembly (1301556).
The working point setting is factory
implemented by means of
potentiometers R9, R11 and R12 and
should not be altered.
5.4.9 (A5-A6) 4-Way Combiner
Assembly, (1301557, low
band/1301558, mid band/1301559,
high band; Appendix D)
This assembly contains (A5-A6-A1) a 4-
way combiner board. There are no
adjustments to the board.
5.4.10 (A5-A6-A2) Circulator
There are no adjustments to the
circulator.
5.4.11 (A6-A1) Dual Peak Detector
Board (1227-1333;Appendix D)
This board is mounted in (A6) a Dual
Peak Detector enclosure (1227-1317).
There are no adjustments to this board.
5.4.12 (A7) Amplifier Protection
Board (1207117;Appendix D)
There are no adjustments to this board.
5.4.13 (A8) Amplifier Control Board
(1265-1414;Appendix D)
To check the operation of the overdrive
circuit, increase the gain pot of the UHF
amplifier tray to approximately 110%.
The Overdrive LED DS2 should light and
the output power should not increase
above the 110% level. If the LED does
not light, adjust the overdrive threshold
as needed.
5.4.14 (A12) +32V/2000W
Switching Power Supply
This switching power supply does not
contain any customer repairable items. If
the power supply should malfunction, do
not attempt to repair the power supply
without first consulting the Axcera Field
Support Department. The power supply
is adjusted to provide an output of +32
VDC.
4-6 kW UHF Translator Chapter 5, Detailed Alignment Procedures
837B, Rev. 0 5-15
5.4.15 Calibration of Output Power
and VSWR Cutback of the Tray
Place a wattmeter and dummy load of at
least 600 watts at the output of the tray
that is to be calibrated and switch the
front panel meter to the % Output Power
position. Preset R16, manual gain, on
(A8) the amplifier control board fully
CCW. Move switch S1 on the amplifier
control board to the Manual position.
Insert a visual-only with a sync-only test
signal to the system and verify 40 IRE
units of sync or insert a digital test
signal. Adjust R16 for 360 watts sync-
only analog, 300 watts 64 QAM or 8-VSB
digital.
To test for analog, using zero span and
aural addition, monitor a sample of the
output with a spectrum analyzer set to
the 0 span position and adjust the
spectrum analyzer so that the level of the
output is at the top line of the graticule.
Insert -10 dB of aural to the visual sync-
only test signal and adjust R16 for the
same reference level on the spectrum
analyzer as with the visual-only input.
The output power on the wattmeter
should be approximately 550 watts visual
and -10 dB aural or 300 watts 64 QAM or
8-VSB digital. Calibrate the front panel
output power meter to 100% with R2,
forward calibration, on the amplifier
control board.
Reduce manual gain pot R16 to a 50%
reading on the front panel meter in the
% Output Power position. Turn off the
tray. Remove the load from the output
of the tray and switch the front panel
meter to the Reflected Output Power
position. Switch on the tray. Adjust
reflected power adjust pot R22 on the
amplifier control board to a 50% reading.
Then adjust R29, the VSWR threshold
cutback pot, on the amplifier control
board until the VSWR Cutback LED DS1
on the front panel just lights. This sets
up the VSWR cutback circuitry. After the
setup is completed, move switch S1 on
the amplifier control board to the
Automatic Gain Control position; this is
the normal operating position for the
switch. The UHF amplifier tray is now
aligned, calibrated, and ready for normal
operation. Repeat as needed for the
other Amplifier Trays in the System
5.5 Phase and Gain Adjustment of
the UHF Amplifier Trays in each
Amplifier Array
Switch the Translator to Standby and
switch Off the Main AC Circuit Breaker
located on each of the AC Distribution
Assemblies in the Amplifier Array
Assemblies. Switch Off all the AC Circuit
Breakers, located on the AC Distribution
Assembly, for the individual Amplifier
Trays.
1. Adjust all gain controls located on
the UHF Amplifier Trays full CCW.
2. Switch On the Main AC Circuit
Breaker for the Side A Amplifier
Array Assembly and switch On the
AC Circuit Breaker for Amplifier #1.
3. Place the Translator in Operate and
adjust the Gain control on the
Amplifier Tray for 50% output
power and adjust the Phase control
to mid range.
4. Monitor the output power of the
Translator by connecting a
Spectrum Analyzer to the Sample
Jack located on the Metering Panel.
Adjust the Spectrum Analyzer for
Zero Span operation. The power
could be monitored by watching the
meters on the panel but the power
change is easier to see on the
analyzer.
5. Turn On the AC to Amplifier Tray #2
and adjust its' output power to
50%.
6. While monitoring the output power
of the Translator, adjust the Phase
Control until the power reaches a
peak. If the Phase adjust reaches
its end of travel, add a 2 inch cable
4-6 kW UHF Translator Chapter 5, Detailed Alignment Procedures
837B, Rev. 0 5-16
to the RF Input (J1) of the amplifier.
Re-adjust the Phase to peak the
System output power. If the Phase
Control again reaches its end of
travel before a peak in power is
reached, remove the 2 inch cable
and add a 3 inch cable to J1 of
amplifier and readjust phase for
peak output power. The adding of
cables should be done during the
adjustment anytime the range of
the phase adjust needs extended.
7. Repeat steps 5 and 6 for the
remaining Amplifiers.
8. Increase the output power on
Amplifier #1 and Amplifier #2 to
90%.
9. Adjust the Phase Control on
Amplifier #2 to peak the System
output power.
10. Increase the output power on
Amplifier #3 to 90% and adjust the
Phase control for maximum System
output power.
11. Increase the output power on
Amplifier #4 to 90% and adjust the
Phase control for maximum System
output power.
12. Increase the output power on
Amplifier #5, if present, to 90%
and adjust the Phase control for
maximum System output power.
13. Increase the output power on
Amplifier #6, if present, to 90%
and adjust the Phase control for
maximum System output power.
14. Monitor the Reflected Power on all
of the UHF Amplifier Trays. The
Reflected Power should read <5%.
If an amplifier is showing high
reflected power adjust the Phase
control to minimize Reflected
Power. Be careful not to increase
Reflected Power on the other
Amplifier Trays. The Amplifier
Trays should interact in such a way
that the phasing of any one
Amplifier will affect the Reflected on
the other Amplifiers.
5.6 Calibration of the Side A and Side
B Amplifier Arrays Forward Output
Power Level
Note: Perform the following
procedure only if the power
calibration is suspect.
Perform the following adjustments with
no aural present by removing jumper
cable W1, the aural IF loop-through that
is connected to J16 on (A5) the sync tip
clamp/modulator board. Connect a sync
and black test signal to the video input
jack of the UHF exciter tray. Switch the
translator to Operate.
Next, set up the translator for the
appropriate average output power level:
• Sync + black 0 IRE setup/wattmeter
= (1309 watts for 4kW) or (1636
watts for 5kW) or (1964 watts for
6kW)
• Sync + black 7.5 IRE
setup/wattmeter = (1200 watts for
4kW) or (1499 watts for 5kW) or
(1799 watts for 6kW)
(2200 Watts peak of sync Visual + 10%
Aural for 4 kW transmitter), or (2750
Watts peak of sync Visual + 10% Aural
for 5 kW transmitter) or (3300 Watts
peak of sync Visual + 10% Aural for 6
kW transmitter)
Note: The translator must have 40
IRE units of sync.
With the spectrum analyzer set to zero
span mode, obtain a peak reference on
the screen. Reconnect jumper cable W1
to J16 on (A5) the sync tip clamp/
modulator board. Turn the gain adjust
pot, located on the front panel of the
Phase/Gain Tray, until the original peak
reference level is attained.
4-6 kW UHF Translator Chapter 5, Detailed Alignment Procedures
837B, Rev. 0 5-17
Begin the power calibration with the
Amplifier Array adjusted to {2200 Watts
(4kW) or 2750 Watts (5kW) or 3300
Watts peak of sync Visual + 10% Aural
for 6 kW transmitter)}.
Side A Forward Power Calibration.
In (A6) the Metering Control Panel,
located in the UHF Exciter Cabinet, find
the (A9) Dual Peak Detector Board
(1159965). Adjust R9 for 100% on the
Side A Power Meter.
Side B Forward Power Calibration.
In (A6) the Metering Control Panel,
located in the UHF Exciter Cabinet, find
the (A8) Dual Peak Detector Board
(1159965). Adjust R9 for 100% on the
Side B Power Meter.
5.7 Calibration of the Side A and Side
B Amplifier Arrays Reflected Output
Level
Monitor the Side A Power Meter, in the
Forward Power position, and turn the
power adjust pot, located on the (A4)
Phase/Gain Tray, to 20%. Move the
cable connected to J3, located on the
(A8) Output Coupler, inside the Side A
Amplifier Cabinet, to Jack J6 and the
cable on J6 to J3. Adjust R10 on (A9)
the Dual Peak Detector Board, located in
the Metering Control Panel, for a 20%
reading in the Reflected Power position.
At this 20% reference power reading, the
VSWR LED mounted on the front panel of
the Exciter Tray should be illuminated. If
the VSWR LED is not illuminated, adjust
R5 on (A18) the Detector Threshold
Board, located in the Metering Control
Panel, until the LED just begins to turn
on. Turn the power adjust pot slightly
CCW and the LED should go out. Turn the
pot CW until the LED just begins to turn
on. The reflected output power for the
amplifier array is now calibrated. Move
the cable connected to J6 back to J3 and
the cable on J3 back to J6, on the (A8)
Coupler.
Monitor the Side B Power Meter, in the
Forward Power position, and turn the
power adjust pot, located on the (A5)
Phase/Gain Tray for Side B, to 20%.
Move the cable connected to J3, located
on the (A8) Output Coupler, inside the
Side B Amplifier Cabinet, to Jack J6 and
the cable on J6 to J3. Adjust R10 on the
(A8) Dual Peak Detector Board, located
in the Metering Control Panel, for a 20%
reading in the Reflected Power position.
At this 20% reference power reading, the
VSWR LED mounted on the front panel of
the Exciter Tray should be illuminated. If
the VSWR LED is not illuminated, adjust
R12 on (A18) the Detector Threshold
Board, located in the Metering Control
Panel, until the LED just begins to turn
on. Turn the power adjust pot slightly
CCW and the LED should go out. Turn the
pot CW until the LED just begins to turn
on. The reflected output power for Side B
is now calibrated. Move the cable
connected to J6 back to J3 and the cable
on J3 back to J6, on the (A8) Coupler.
5.8 Phase and Gain Adjustment
Procedure for entire Amplifier Array
Assembly
1. Begin the alignment with all
Amplifier Trays up and running.
Monitor the Reject Power by setting
the Combined Metering switch to
the Reject position and adjusting
the Phase Control on either, or
both, of the Phase/Gain Modules to
minimize the Reject reading.
2. Adjust the Amplifier Gain controls
so that all amplifiers have equal
output power.
3. The Gain control on the Phase/Gain
Module can be used to balance the
output power between Sides A and
B. This adjustment has a 10%
range. If the end of its' range is
reached, you must adjust the gain
of each amplifier in the Amplifier
Side to balance the power of each
Side.
4-6 kW UHF Translator Chapter 5, Detailed Alignment Procedures
837B, Rev. 0 5-18
5.9 Calibration of the Forward
Output Power Level of the Translator
Note: - Perform the following only if the
power calibration is suspect.
Switch the Translator to Standby and
preset R51, Aural Null pot, located on the
Visual/Aural Metering Board (1265-1309)
in the Metering Panel, full CCW. Adjust
R48, the Null Offset pot, located on the
Visual/Aural Metering Board, for 0%
Visual Output. Do the following
adjustments with no Aural present, by
removing the Jumper Cable W1, Aural IF
Loop-Thru, connected to J16, located on
the Sync Tip Clamp/Modulator Board
(1265-1302) in the selected UHF Exciter.
Connect a Sync and Black Test Signal to
the Video Input Jack J2 on the Remote
Interface Assembly of the UHF Exciter
Tray. Switch the Translator to Operate.
Next, set the Translator up for the
appropriate Average Output Power Level.
Peak of Sync Visual + Black 0 IRE Setup
equals; for 4 kW 2380 Watts, for 5 kW
2975 Watts and for 6 kW 3570 Watts.
Peak of Sync + Black 7.5 IRE Setup
equals; for 4 kW 2180 Watts, for 5 kW
2725 Watts and for 6 kW 3270 Watts.
NOTE: Must have 40 IRE Units of Sync.
Adjust R28, Visual Calibration, located on
(A10) the Visual/Aural Metering Board
(1265-1309) in the Metering Panel, for
100% on the front panel Combined Meter
in the % Visual Position.
With the Spectrum Analyzer set to Zero
Span Mode obtain a peak reference on
the screen. Reconnect the Jumper Cable
W1 to J16 located on (A5) the Sync Tip
Clamp/Modulator Board in the UHF
Exciter. While in the Combined Visual
Output Power position, adjust L3 for
minimum visual power reading. Turn the
power adjust pot on the front panel of
the Exciter until the original peak
reference level is attained. Switch to the
Combined Aural Output Power position
and peak L1 and C8 for maximum Aural
Power reading. Then adjust R20 also for
100% Aural Power reading. Switch to
Combined Visual Output Power position
and adjust R51 for 100% Visual Power.
5.10 Calibration of the Reflected
Output Level of the Translator
Turn the Power Adjust Pot on the UHF
Exciter to 20% on the Metering Panel
Combined Meter in the Visual Power
position. NOTE: Check that the Jumper
is in Manual on the UHF Upconverter
Board (1265-1310) in the UHF Exciter.
On (A11) the Output Coupler for the
Translator, move the cable on J6 to J5
and the Termination on J5 to J6. Adjust
R10 on the (A7) Dual Peak Detector
Board (1159965), in the Metering Panel,
for a 20% reading in the Combined
Reflected Power position. At this 20%
Reference Power reading, the VSWR LED
mounted on the front panel of the UHF
Exciter should be illuminated. If not
adjust R19 on the Detector Threshold
Board, in the Metering Control Panel,
until the VSWR LED just turns On. Turn
the Power Adjust pot slightly CCW and
the LED should go out, turn the pot CW
until the LED just turns On. The
Reflected Output Power is now calibrated.
Switch the Translator to Standby. Move
the cable on J5 to J6 and the Termination
on J6 back to J5. Switch the Translator
to Operate and adjust the front panel
power pot for 100% Visual Power reading
on the Combined Meter.
5.11 Calibration of the Reject Power
of the Translator
Check that the System is operating at
100% Output Power. Remove the AC
power to the Side A Amplifier Array by
switching Off CB1 the Main AC circuit
breaker, located on the AC Distribution
Panel for the Side A Amplifier Array.
Adjust R9 on the (A7) Dual Peak Detector
Board, located in the Metering Control
Panel, for a 25% Power reading in the
reject power position. The Reject power
is now calibrated.
4-6 kW UHF Translator Chapter 5, Detailed Alignment Procedures
837B, Rev. 0 5-19
Return CB1, the Main AC circuit breaker
for the Side A Amplifier Array, to the On
position.
5.12 IF Phase Corrector Adjustment
of the Translator
As shipped, the exciter was preset to
include linearity (gain vs. level) and
phase (phase vs. level) predistortion. The
predistortion was adjusted to
approximately compensate the
corresponding non-linear distortions of
the amplifier trays and should not require
additional adjustments.
Locate (A9) the IF phase corrector board
(1227-1250) mounted in the UHF exciter.
Because the amplitude correction portion
of the board is not utilized in this
configuration, the jumper W3 on J10
should be in the disable position, to +6.8
VDC, and R35 and R31 should be fully
CCW. R68 is the range adjustment and
should be set in the middle of the range.
The phase correction enable/disable
jumper W2 on J9 should be in the enable
position to ground.
Switch the video input test source to
select an NTSC 3.58-MHz modulated
staircase or ramp test waveform and set
up the station demodulator and
monitoring equipment to monitor the
differential phase or intermodulation
products of the RF output signal. There
are three corrector stages on the IF
phase corrector board, each with a
magnitude and a threshold adjustment,
that are adjusted as needed to correct for
any differential phase or intermodulation
problems. If necessary, adjust the R3
threshold for the cut-in point of the
correction and the R7 magnitude for the
amount of the correction.
Jumper W1 on J8 is set to give the
desired polarity of the correction that has
been shaped by the threshold R11 and
magnitude R15 adjustments. After
setting the polarity, adjust the R11
threshold for the cut-in point of the
correction and the R15 magnitude for the
amount of the correction that is needed.
Finally, adjust the R19 threshold for the
cut-in point of the correction and the R23
magnitude for the amount of the
correction that is needed.
Note: Adjusting these pots changes
all visual parameters and should be
done cautiously.
On the IF phase corrector board (1227-
1250), preset pots R7, R15, R23, and
R35 fully CW and R3, R11, R19, and R31
fully CCW.
Set the waveform monitor to differential
step filter and the volts/division scale to
.1 volt. Center the display around
blanking.
Gradually adjust pots R3, R11, and R19
CW, as needed, on the IF phase corrector
board to minimize the observed thickness
of the intermodulation as seen on the
display.
While performing the preceding
adjustments, the intermodulation beat
products between the colorburst and the
aural carrier at 920 kHz above visual
carrier should be observed on the
spectrum analyzer. The frequency will
vary for different video systems. When
the adjustments are performed properly,
the intermodulation products on the
spectrum analyzer should be at least -52
dB down, with a red field input, from
peak visual carrier. The intermodulation
distortion, as displayed on the waveform
monitor, should be no more than 1 unit
of IRE. The pot R31 on the IF phase
corrector board is used for any extra
intermodulation corrections that may be
needed.
Note: Any adjustment to the above
pots affects other visual parameters
and some slight adjustments to all of
the pots may be needed to
simultaneously meet all of the
specifications.
4-6 kW UHF Translator Chapter 5, Detailed Alignment Procedures
837B, Rev. 0 5-20
5.13 Linearity Corrector Adjustment
for Translator
The IF linearity correction function
consists of three non-linear cascaded
stages, each having adjustable
magnitude and threshold, or cut-in
points, on the ALC board. The threshold
adjustment determines at what IF signal
level the corresponding corrector stage
begins to increase gain. The magnitude
adjustment determines the amount of
gain change for the part of the signal that
exceeds the corresponding threshold
point. Refer to the UHF exciter tray
assembly drawing (1245-1100) and the
ALC board parts location drawing (1265-
5305) for the adjustments for the first
through third linearity corrector stages.
Because the stages are cascaded, the
order of correction is important. The first
stage should cut-in near white level, with
the cut-in point of the next stage toward
black, and with the last stage primarily
stretching sync.
To initially adjust the linearity correctors,
make sure that the translator is
operating at full power with the desired
A/V ratio. Check that the jumper W1 on
J4 on the ALC board is enabled, between
pins 1 and 2. Check that the ALC voltage
is set to +0.8 VDC as monitored on the
front panel meter in the ALC position.
Insert a modulated ramp video test
signal into the video input connector on
the remote interface panel of the
translator. Demodulate the output signal
of the translator and observe the
waveform on a waveform monitor while
also looking at the signal on a spectrum
analyzer. On the IF ALC board (1265-
1305), preset pots R34, R37, and R40
(threshold) fully CCW, and the magnitude
adjustments R13, R18, and R23 fully CW.
Adjust pots R34, R37, and R40 CW on
the IF ALC board, as necessary, to give
correction at sync or at low luminance
levels; these are viewed at the right-
hand edge of the waveform monitor.
If the translator is being driven very
hard, it may not be possible to get
enough sync stretch while maintaining a
flat differential gain. In this case, some
video sync stretch may be used from the
sync tip clamp on the modulator board.
The sync stretch adjustment is R48 on
the sync tip clamp on the modulator
board. Switch the translator to Standby.
The Translator is fully aligned and ready
for normal operation.