User's Manual

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connect the left spectrum analyzer to a particular test point, left-click on the
green test point. Its color will change to red. Right-clicking on a dot will
connect it to the right analyzer, and the color will change to blue. If both
displays are connected to the same test point, the point color will turn
magenta.
Within the displayed spectra, a red color frequency cursor can be manually
dragged, using the left mouse button, over a particular spectral component.
The two
Vector Voltmeter
displays labeled Left/Right indicate the relative
amplitude and phase difference between the two spectral components at the
cursor frequency.
There are two additional tools provided in this window:
THD
(total harmonic
distortion) and
SINAD
(signal-plus-noise-plus-distortion to noise-plus-
distortion) meters. They can be used to test the overall receiver performance
as well as provide indication of the sound card quality. To use these
facilities, a pure tone-modulated signal must be applied to the receiver
antenna input, and the frequency of the modulating tone must be equal to
the
Test freq
setting.
When either of the
THD
or
SINAD
buttons is activated, the right-hand
spectrum display will be automatically connected to the end of the
demodulator chain (i.e. right-clicking on any other test points will not work
until both the
THD
and
SINAD
buttons are released).
For synchronous demodulation of amplitude modulated signals (the
AMS
mode) without carrier or with a fluctuating one, the G3 SERIES Professional
Demodulator uses a PLL carrier recovery technique based on the Costas
loop:
Synchronous AM Demodulator Structure