LOCAL OPERATION
3-60
Look and Listen
C6055
RF
DET.
LOCAL
OSCILL-
ATOR
RECEIVER
CIRCUITS
AUDIO
AMP.
SWEEP
GEN.
OSCILLO-
SCOPE
LOG.
AMP.
AM/FM
DEMOD
20 dB
ATTEN.
I/O
SWITCH-
ING
!
!
Fig. 3-15 Spectrum Analyzer setup, Look and Listen function
The optional Look and Listen facility allows the instrument to be used for ‘OFF-AIR’ monitoring
of transmissions while examining the area of radio spectrum on which the transmission being
monitored is centered. The width of RF spectrum scanned in the Look and Listen mode is
adjustable in steps from a minimum of 100 kHz to 1 MHz.
The RF signal from a suitable antenna is coupled to the Service Monitor through either the antenna
BNC connector or the ‘N type’ connector on the front panel. The signal is passed through the
spectrum analyzer circuits to be displayed as a conventional spectrum analyzer display. The listen
demodulator obtains its signal from a non-sweeping IF circuit and is tuned to the center frequency
of the display. The output from it is routed through an AF amplifier to the internal loudspeaker, to
the accessory socket and to the ‘demod out’ socket. See Fig. 3-15, Spectrum Analyzer setup, Look
and Listen function.
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