HP 8444A - Page 23

Model 8444A
Figure 8-7. 23 MHz Low-Pass Filter CRT Display
3-19. Swept Return Loss Measurement
3-20. Figure 3-8 illustrates the CRT display for a
swept return loss or reflection coefficient measure-
ment. A directional bridge (HP 8721A) was used to
separate the incident from the reflected signal. The
filter under test is the same 23-MHz Low-Pass (para-
graph 3-18). Control settings same as paragraph
3-18 except analyzer gain adjusted so that the top
graticule line represents 0 dB return loss or total
reflection (e.g. a short or open circuit). Return loss
is greater than 15 dB (00.18, SWR 1.44) over the
filter range of 0 to 23 MHz.
Figure 3-8. Swept Return Loss Measurement
CRT Display
3-21. Amplifier Gain and Bandwidth Measurement
3-22. Figure 3-9 illustrates the CRT display for a
1 to 400 MHz amplifier with gain of approxi-
mately 19 dB. A reference level is first established
by connecting the Tracking Generator output to the
Spectrum Analyzer (through a 30 dB attenuator)
and scanning over the range of interest. The ampli-
fier is then connected between the Tracking Gener-
ator and the Spectrum Analyzer and the same
Operation
frequency range scanned. The Spectrum Analyzer
(8554B) set to full scan (0--1250) provides a CRT
display indication as follows: 3-dB bandwidth
approximately 500 MHz (level at +1 graticule line)
and zero gain point of approximately 1025 MHz.
a 30 dB Coaxial Attenuator installed at
Tracking Generator RF OUTPUT.
b. Spectrum Analyzer (8554B) control
settings:
BANDWIDTH solera ets 800 KHZ
SCAN WIDTH ...............-..0—-1250 MHz
INPUT ATTENUATION .............. 10dB
SCAN TIME PER DIVISION 10 MILLISECONDS
LOG/LINEAR 2.4. pe ak rada LOG
LOG REF LEVEL 2.240.022: 710. dBm
VIDEO PIETER ssp ra ees eye OFF
SCAN MODE „2448 500 Op aie ae bods eda .. INT
SCAN TRIGGER 4 waw gawa a AUTO
c. Tracking Generator control settings:
TRACK ADS: ua. ned zen, Peak
A Diocese Oech ra wn biwara Rage DUB
Figure 8-9. Amplifier Gain and Bandwidth
CRT Display
3-23. Precision Frequency Measurements
3-24. An external frequency counter may be used
with the Tracking Generator/Spectrum Analyzer
System for frequency measurements at any point
on the CRT display. With the counter connected to
the Tracking Generator AUX RF OUTPUT jack
(rear panel) and the system operated in the
MANUAL SCAN mode; the scan can be stopped at
any point for frequency measurement.
CAUTION
Do not leave System stopped in MAN-
UAL SCAN with high INTENSITY. Dam-
age to the display CRT can result.