9) Check that the 4.2 GHz (5.5 GHz, Option 01) marker
is within 8.4 MHz (11.0 MHz, Option 01) of screen
center. (If the error is large it may be necessary to
change the SPAN/DIV to 5 MHz.) If the error is
greater than 8.4 MHz (11.0 MHz, Option 01) proceed
with the next step, if not proceed to paragraph
1 1
.
10) Center the 4.2 GHz (5.5 GHz, Option 01) marker on
screen with the FREQUENCY control.
a) If the readout is equal to or greater than
4.216 GHz (5.522 GHz Option 01) adjust the 1st
LO Offset R1032, on the 1st LO Driver board,
(Fig. 3-31) to move the marker 4 MHz (5.5 MHz,
Option 01) lower.
b) If the readout is between 4.208 and 4.216 (5.511
and 5.522, Option 01) adjust R1032 to move the
marker one half the difference between the error
and 4.208 GHz (5.511 GHz, Option 01); for ex
ample, a readout of 4.212 would require a 4.210
(4.212 - 4.208) correction.
11) Tune the FREQUENCY readout to 4.207 GHz (5.510
GHz, Option 01) and adjust the 1st LO Sensitivity
R1031, on the 1 st LO Driver board, (Fig. 3-31) so the
marker is at center screen.
12) Recheck readout accuracy as described in the Per
formance Check part (step 2) of this section, across
band 1 (band 1 and 2 of Option 01 instruments) to
ensure that the accuracy is within performance
requirement.
ALTERNATE PROCEDURE TO CALIBRATE FRE
QUENCY SPAN
TO
CENTER
FREQUENCY
READOUT, FOR 492P INSTRUMENTS.
Instructions for the 4050 program are given in
parentheses.
1
. Send
■INIT.REF -20,'SPAN 2M;SIG”
■FREQ
100M;DEG;SIG; WAIT; FREQ
1.8G;DEG;-
SIG;WAIT; REP 1200”
This
will give an adjustment sequence for about two min
utes.
If necessary, re-send the command to complete the
adjustm ent.
(Press USER key 3 to start the sequence and press the
BREAK key to stop.)
Calibration—492/492P Service Vol. 1 (SN B030000 & up)
Adjustment Procedure
2.
If the adjustments are fairly close, two signals will ap
pear on screen on alternate sweeps; a large and a small
signal. The small signal is 1
. 8
GHz, the large at
1
00 MHz.
Proceed with the following adjustments:
a) Adjust the 1st LO Offset R1032 on the 1st LO
Driver board, to bring the two signals to the same
horizontal position. If one or no signals appear on
screen, adjust R1031 until a signal comes on
screen. Then adjust R1032 (1st LO Offset) until
the second signal appears while alternately ad
justing the 1st LO Sense R1031 to keep the first
■
■
signal on screen.
b) Adjust 1 st LO Sense R1031, on the 1 st LO Driver
board, to align the two signals with the vertical
centerline of the graticule.
c) Send “FREQ 4.2 G;DEG”
(For Option 01, send; “FREQ 5.5 G; Deg”)
d) If the marker is greater than
8 . 6
MHz (11.0 MHz,
Option 01) perform steps d(10) and d(11)
e) Recheck across band 1 by re-sending the 4050
program of paragraph
1
above and repeat para
graph
2
procedure.
e. Adjust 1st LO Sweep (Applicable to both 492 and
492P instruments)
1) With the Calibrator output applied to the RF IN
PUT, set the FREQ SPAN/DIV to 100 MHz and
tune the FREQUENCY to about 500 MHz.
2) Adjust Tune Coil Swp R1065 (Fig. 3-31) on the
Span Attenuator board so the 100 MHz harmonics
of the Calibrator are spaced at one division inter
vals over the center eight divisions of the graticule.
Adjust the FREQUENCY as necessary to align the
markers.
3) Remove the Calibrator signal.
4) Set the FREQ SPAN/DIV to 2 MHz, REF LEVEL to
+ 10 dBm, FREQUENCY about 15 MHz, then ap
ply 0.5 μβ markers from a time-mark generator to
the RF INPUT.
5) Adjust the 1st LO FM Coil Swp R1071 (Fig. 3-31)
for
1
marker/division over the center eight divisions
of the display.
f. Max Span Dot (Offset to align dot with display).
a) Remove 50 Ω cable from 492 RF INPUT.
b) Set 492 CENTER FREQUENCY to exactly 0 MHz,
AUTO RESOLUTION pushbutton on, FREQ
SPAN/DIV to MAX, and VIEW A and VIEW B both
OFF.
c) Select R1028 on the YIG Driver board to set the
MAX SPAN DOT directly on the Start Spur. See
Fig. 53B.
NOTE
A larger resistor will move the Dot to the right and a
smaller resistor will move it to the left. A 1K change in
resistance will move the dot approximately one minor
division.
3-52
REV NOV 1982
