2 1. Frequency Response Adjustments
clockwise to increase the level of the displayed signal responses
above 500 MHz.
It might be helpful to increase or decrease the spectrum analyzer
[
SWEEP TIME
)
setting while adjusting
A2 and
Al,
particularly when making fine adjustments. An increase in spectrum
analyzer sweep time results in closer spacing of the displayed
responses, but slows the adjustment.
36.
37.
38.
39.
On the synthesized sweeper, key in
LEVELING,
[
SWEEP
S
WEE
P
SW
EEP
On the spectrum analyzer, key in SWEEP TIME
TRACE B
(
CLEAR
-
WRITE
],
TRACE B
On
the
synthesized sweeper, press SWEEP
and wait for
a sweep to complete (150 seconds) and the SWEEP LED to turn
off. As the synthesized sweeper tunes from 10 MHz to 2.5
the
input signal should be displayed as a TRACE A response, and
the spectrum analyzer frequency response should be displayed as
TRACE B, as shown in Figure 3-93.
S T A R T
M H Z
S T O P 2
3 MHZ
3 MHZ
5 2 . 3
Figure 3-93.
Typical Frequency Response (10 MHz 2.5
On the spectrum analyzer, key in TRACE B
TRACE A
MARKER
and use the DATA knob to position a
marker on the lowest point on the TRACE B waveform. Then,
press MARKER
MARKER
(
PEAK SEARCH
)
to position a second
marker on the highest point on the TRACE B waveform. Total
peak-to-peak deviation of the displayed trace should be less than
1.20
To provide the spectrum analyzer with a 10 MHz to 2.5
input
signal of sufficient flatness for measuring frequency response, the
synthesized sweeper must be leveled externally with a power meter
with a relatively slow sweep time (at least 40 seconds). However,
relative flatness adjustments are made with the synthesized sweeper
82 Adjustments
