Rf Section; A7 Loda; A8 Low Band Mixer; A9 Input Attenuator - HP 8560A Service Manual

RF Section

The RF Section includes the following assemblies:
A7 LODA (LO Distribution Amplifier)

A8 Low Band Mixer

A9 Input Attenuator

A10 Tracking Generator (Option 002)
All YTO (YIG-Tuned Oscillator)

Al3 Second Converter

Al4 Frequency Control Assembly (also in Synthesizer Section)
Al5 RF Assembly (also in Synthesizer Section)
The RF Section converts all input signals to a fixed IF of 10.7 MHz. The RF Section's
microcircuits are controlled by signals from the Al4 Frequency Control and Al5 RF
assemblies.
The HP 8560A Spectrum Analyzer uses triple conversion to produce the 10.7 MHz IF and
a fourth conversion used only in 100 Hz, 30 Hz, and 10 Hz resolution bandwidths. A8 Low
Band Mixer up-converts the RF input to a first IF of 3.9107 GHz. Al3 Second Converter
down-converts the 3.9107 GHz IF to an IF of 310.7 MHz. A third conversion on the Al5 RF
assembly down-converts the second IF to the 10.7 MHz third IF. A fourth conversion on the
A4 Log Amplifier assembly down-converts the third IF to the 4.8 kHz fourth IF used only in
100 Hz, 30 Hz, and 10 Hz resolution bandwidths.

A7 LODA

The A7 LODA (LO Distribution Amplifier) levels the output of the All YTO and distributes
the power to the front-panel 1ST LO OUTPUT, A8 Low Band Mixer, Option 002 Tracking
Generator, and A15A2 Sampler. The leveling circuitry is on the Al4 Frequency Control
Assembly.
A8 Low Band Mixer
A8 Low Band Mixer is dc-coupled and contains a limiter.
A9 Input Attenuator
The attenuator is a 500 precision, coaxial step attenuator. Attenuation in 10 dB steps from
0 dB to 70 dB is accomplished by switching the signal path through one or more of the three
resistive pads. The attenuator automatically sets to 70 dB and DC block when the analyzer
turns off, providing ESD protection. (Note that the input attenuator is not field-repairable.)

All YTO

All is a YTO (YIG-Tuned Oscillator). YIG (yttrium-iron-garnet) is a ferro-magnetic material
which is polished into a small sphere and precisely oriented in a magnetic field. Changes in
this magnetic field alter the frequency generated by the YTO. Current control of the magnetic
field surrounding the YIG sphere tunes the oscillator to the desired frequency.
6-36 General Troubleshooting