2 1. Frequency Response Adjustments
126.
127.
128.
129.
the high end of the band drop in amplitude by approximately
0.75
Readjust 22-turn (IF Offset) potentiometer
D as
necessary to maximize the overall level of the displayed signal
responses from 12.5
to 18.6
on the spectrum analyzer
display. If the displayed signal responses peak at widely different
settings of
D, perform the following steps:
a. Adjust 22-turn (YTX Linearity) potentiometers
LB2,
LB3,
LB4,
LR2,
LR3, and
LR4 fully counterclockwise
if they have not already been so adjusted; do
not
readjust
LB1 or
b. Readjust 22-turn (IF Offset) potentiometer
D as
necessary to maximize
the
overall level of the displayed signal
responses at the low end of the band.
c. On the spectrum analyzer, key in MARKER
and
position
the
marker at the point in the band where the signal
responses begin to fall off from their maximum value.
d. Adjust 22-turn (YTX Linearity) potentiometer
LB2
clockwise until the displayed signal responses at the high end
of the band begin to drop. Continue to adjust
LB2
until the
point aligns with the position of the marker.
See Figure 3-90 for the location of
LB2,
LB3,
LR2 and
LR3.
e. Readjust 22-turn (YTX Linearity) potentiometer
LR2 clockwise to maximize the displayed signal responses for
approximately 3 divisions to the right of the marker.
f. On the spectrum analyzer, key in MARKER
and
position the marker at the point in the band where the signal
responses begin to fall off from their maximum value.
g. Readjust 22-turn (YTX Linearity) potentiometer
LB3 clockwise until the displayed signal responses at the high
end of the band begin to drop. Continue to adjust
LB3 until the
point aligns with the position of the
marker.
h. Readjust 22-turn (YTX Linearity) potentiometer
LR3 clockwise to maximize the displayed signal responses at
the high end of the band.
i. Readjust
D,
LR2, and
LR3
as necessary to maximize the displayed signal responses from
12.5
to 18.6
on the spectrum analyzer display.
Gradually readjust (Band D Lower Segment)
and (Band D Upper Segment)
D2 as necessary for
maximum flatness of the displayed signal responses.
On the spectrum analyzer, key in SWEEP
[
SWEEP TIME
)
TRACE A [BLANK), TRACE B
6, TRACE B
5,
Press SWEEP
on the spectrum analyzer and wait for the
sweep to complete (150 seconds) and the SWEEP LED to turn
off. As the spectrum analyzer tunes from 12.5
to 18.6
the spectrum analyzer frequency response should be displayed as
TRACE B.
3-196 Adjustments
