Chapter 7 353
General Troubleshooting
Block Diagram Description
RF Section
The RF section of the 8564EC and 8565EC includes the following
assemblies:
A7 LOMA (LO multiplier/amplifier)
A8 low band mixer
A9 input attenuator
A10 RYTHM (YIG-tuned filter/mixer)
A11 YTO (YIG-tuned oscillator)
A12 SBTX (switched barium-tuned mixer)
A13 second converter
A14 frequency control assembly (also in synthesizer section)
A15 RF assembly (also in synthesizer section)
FL1, FL2, FL3, and FL5 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 A14
frequency control and A15 RF assemblies.
Band 0 .............................................................. 9 kHz to 2.9 GHz
Bands 1 through 3 .............................................. 2.9 to 26.5 GHz
Bands 4 and 5 ...................................................... 26.5 to 50 GHz
Band 0 and bands 4 and 5 use triple conversion to produce the
10.7 MHz IF, and a fourth conversion used only in the digital resolution
bandwidths (≤100 Hz). In band 0, A8 low band mixer up-converts the
RF input to a 1st IF of 3.9107 GHz. In bands 4 and 5, A12 SBTX
down-converts the RF input to a 1st IF of 3.9107 GHz. A13 second
converter down-converts the 3.9107 GHz IF to an IF of 310.7 MHz. A
third conversion on the A15 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 (≤100 Hz).
Bands 1 through 3 use double conversion. A third conversion is used for
the digital resolution bandwidths (≤100 Hz). A10 RYTHM
down-converts the RF input to a 1st IF of 310.7 MHz. Although this IF
passes through the A13 second converter, it bypasses the second mixer.
The second conversion on the A15 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 (≤100 Hz).
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