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When triggered, the attenuators effectively attenuate the signal level at the
input to the RMS Rectifier by 20 dB and boost its output by an equal
amount. The attenuators are automatically reset by the Switching Circuit
when the meter indication falls to 25 dB below FSD. The 5 dB difference
between the Switching Circuit triggering levels removes the possibility of
signal ripple causing the dynamic range to be extended accidentally. The
overall RMS circuit gain is therefore not changed, but the dynamic range is,
and is extended to 50 dB.
The linear DC output from the RMS Rectifier which is now proportional
to the RMS value of the signal applied to the 2010 is amplified 10 dB by the
final stage of the RMS circuit and passed to the display meter, either direct-
ly or via the Lin/Log converter. The RMS value can be read directly from
the meter when it is used with any one of the appropriate Lin or Log scales
supplied with the 2010.
5.3. ANALYZER SECTION
The block diagram of the analyzer and oscillator section is shown in
Fig.5.7. The analyzer section is driven by the two oscillators of the BFO
section:
a) a fixed frequency crystal oscillator, connected to frequency con-
verters which provide all the fixed frequencies necessary, and
b) a voltage controlled oscillator (V.C.O.) which provides the variable
frequency.
5.3.1. Fixed Frequency Oscillator
The fixed frequency oscillator is a quartz crystal parallel resonance type
oscillator which generates approximately 1 Volt peak-to-peak at a frequency
of 960kHz.
The signal then is processed by frequency converters which produce the
following frequency outputs:
46
f
0
=
1.20 MHz for the B.F.O. and an external output
f
1
=
1.23 MHz for the second mixer and the V.C.O. stabilization
f
2
=
30.75 kHz for the 3rd mixer
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