2 1. Frequency Response Adjustments
SWEEP TIME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ms
SWEEP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CONT
148. On the spectrum analyzer, key in TRACE A
[
CLEAR
-
WRITE
),
MARKER (OFF),
As the spectrum
analyzer completes each sweep, a series of approximately 23 new
responses should be displayed. The peaks of these responses
coarsely outline the spectrum analyzer frequency response.
149. Gradually adjust (Band E Lower Segment)
El and
(Band E Upper Segment)
E2 for maximum flatness of
the displayed signal responses. The adjustments are interactive,
with
El having the most effect on the level of the
displayed signals below mid-band (approximately 20.3
and
E2 having the most effect on the level of
the displayed signals above mid-band. Adjust
El
counterclockwise to increase the level of the displayed signal
responses below mid-band. Adjust
E2 clockwise
to increase the level of
the
displayed signal responses above
mid-band. See Figure 3-90 for the locations of
El and
E2.
If the displayed signals at the high end of the band drop off by more
than 3-4
center
E2 and proceed to step 150.
150. On the spectrum analyzer, key in
[
SWEEP TIME
)
LOG SCALE
C
ENTER
1
TRACE B (VIEW),
4,
TRACE B
151. Readjust
(YTX Diode Bias) potentiometer
VE
to maximize the overall level of the displayed signal responses
from 18.6
to 22.0
on the spectrum analyzer display.
Then, adjust
VE clockwise until signal responses at
the high end of the band drop in amplitude by approximately 1.5
152. Readjust 22-turn (IF Offset) potentiometer
E as
necessary to maximize the
level of the displayed
responses from 18.6
to 22.0
on the spectrum analyzer
display. If the displayed
responses peak at widely different
settings of
E, perform the following steps:
a. Adjust 22-turn (YTX Linearity) potentiometers
LB4
and
LR4 fully counterclockwise if they have not
already been so adjusted;
do
not readjust
LB2,
LB3,
LR2, or
LR3.
b. Readjust 22-turn (IF Offset) potentiometer
E 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. Readjust 22-turn (YTX Linearity) potentiometer
LB4 clockwise until the displayed signal responses at the high
end of the band begin to drop. Continue to adjust
LB4 until the
point aligns with the position of the
Adjustments
99
