Chapter 8 433
IF Section
A5 IF Assembly
CAUTION For troubleshooting, it is recommended that you use an active probe,
such as an HP 85024A, and another spectrum analyzer. If an HP 1120A
active probe is being used with a spectrum analyzer having dc-coupled
inputs, such as the HP 8566A/B, HP 8569A/B and the HP 8562A/B,
either set the active probe for an ac-coupled output or use a dc-blocking
capacitor between the active probe and the spectrum analyzer input.
CAUTION Do not short control voltages to ground. These voltages are not
short-circuit protected. DACs damaged by shorting these voltages
might not fail until several weeks after the shorting takes place.
Do not short power-supply voltages to ground. The spectrum analyzer
power-supply current limiting cannot protect the resistors in series
with the power supply.
NOTE Some transistors have collectors connected to the case. Electrical
connection of the case to the collector might not be reliable, making
collector voltage measurements on the transistor case unreliable.
IF Signature
1. Disconnect W27 (coax 3) from A5J5.
2. Connect an SMB tee to A5J5, using a short coaxial cable with SMB
connectors.
3. Connect one output of the tee to cable W27 (coax 3).
4. Connect an HP 85024A active probe, with a 10:1 divider installed, to
the other output of the tee.
5. Connect the output (type N connector) of the active probe to the
input of the HP 8566A/B spectrum analyzer.
6. Connect the probe power cable to the HP 8560E/EC front panel
PROBE POWER connector (you may need to use a probe power
extension cable, HP 10131B).
7. Set the HP 8566A/B controls as follows:
Reference level ......................................................... +10dBm
Center frequency .................................................... 10.7MHz
Span .................................................................................0Hz
Resolution bandwidth .............................................. 300kHz
Video bandwidth ....................................................... 300kHz
Sweep time ....................................................................... 5.5s
Trigger .......................................................................... Single
8. On the HP 8566A/B, press
SHIFT (trace A blank) to set detector to
SAMPLE mode.
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