RF
Section
The RF section includes the following assemblies:
A7 SLODA (switched LO distribution amplifier)
A8 low band mixer
A9 input attenuator
A10 YIG-tuned filter/mixer (RYTHM)
All YTO (YIG-tuned oscillator)
Al3 second converter
Al4 frequency control assembly (also in synthesizer section)
Al5 RF assembly (also in synthesizer section)
FLl,
FL2 low-pass filters
The RF section converts all input signals to a fixed IF of 10.7 MHz. The RF section
microcircuits are controlled by signals from the Al4 frequency control and Al5 RF assemblies.
Band 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 kHz to 2.9 GHz
Bands 1 through 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.2.75
to 13.2 GHz
Band 0 uses triple conversion to produce the 10.7 MHz IF and a fourth conversion used
only in the digital resolution bandwidths
(5100
Hz). 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 the digital resolution
bandwidths
(5100
Hz).
Bands 1 and 2 use double conversion. A third conversion is used for the digital resolution
bandwidths
(<lo0
Hz). A10 YIG-tuned filter/mixer (RYTHM) down-converts the RF input
to a first IF of 310.7 MHz. Although this IF passes through the Al3 second converter, it
bypasses the second mixer. The second conversion on the Al5 RF assembly down-converts
the 310.7 MHz IF to 10.7 MHz. A third conversion on the A4 log amplifier assembly
down-converts the second IF to the 4.8 kHz third IF used only in the digital resolution
bandwidths
(5100
Hz).
A7 SLODA
The A7 SLODA
(
switched LO distribution amplifier) levels the output of the All YTO
and distributes the power to the front-panel First LO OUTPUT, A8 low band mixer, A10
YIG-tuned filter/mixer, and
A15UlOO
sampler. The leveling circuitry is on the Al4 frequency
control assembly.
A8 Low Band Mixer
A8 low band mixer is ac-coupled and contains a limiter. The high band mixing is done in
the A10 YIG-tuned filter/mixer. A PIN diode switch in A10 directs the RF input to the
appropriate mixer. A PIN diode switch in A7 SLODA directs the first LO to the appropriate
mixer. Low band mixer power is provided by the Al4 frequency control assembly.
General Troubleshooting 7-43
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