Yaesu FT DX 9000 CONTEST - 2, Руководство по эксплуатации

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Page 56 FT
DX
9000 C
ONTEST
O
PERATION
M
ANUAL
CONTOUR knob
CONT switch
B
C
A
CONTOUR C
ONTROL
O
PERATION
The Contour filtering system provides a gentle perturbation of the IF filter passband, so as to suppress or enhance certain
frequency components modestly, so as to enhance the natural-sounding received signal.
I
NTERFERENCE
R
EJECTION
(S
IGNALS WITHIN
3
KHZ
)
1. Press the CONT switch (# ). The LED imbed-
ded in the switch will glow Red to confirm that the
Contour filter is engaged.
2. Rotate the CONTOUR knob (# ) to achieve the
most natural-sounding audio reproduction on the in-
coming signal. To cancel Contour tuning, press the
CONT switch once more.
Advice
When the optional Data Management Unit (DMU-
9000) and TFT Display Unit (TFT-9000) are installed,
you may use the Audio Scope on the Audio Scope/
Oscilloscope page on the TFT to help you adjust the
setting of the Contour control for the optimum perfor-
mance. The effect of the Contour filter adjustments
within the Audio Scope passband will be easy to see
on the Audio Scope.
The Width of the Contour filter effect, and the degree
of nulling or peaking, may be adjusted using the menu.
The Contour filter’s level (either nulling or peaking) may be
adjusted using Menu Item “
RX DSP 078 MAIN-CONTOUR-
LEVEL .” The factory default setting is –15.
The bandwidth over which the Contour filter effect is applied
may be adjusted using Menu Item “
RX DSP 079 MAIN-
CONTOUR-WIDTH .” The factory default setting is 10.
Quick Point
The steep slopes of the DSP filtering can, when adjusted
aggressively, impart an unnatural sound to an incoming
signal. Oftentimes, though, a narrow bandwidth is not the
key to improving copy; the incoming signal itself may have
undesirable or excessive frequency components, especially
in the low-frequency range around 400 Hz. By judicious
use of the Contour filter, the “shoulder” of the passband
response may be altered, or components removed from
within the passband, allowing the desired signal to rise
above the background noise and interference in a manner
not obtainable with other filtering systems.
IF
BANDWIDTH
IF
BANDWIDTH
IF
BANDWIDTH
With reference to Figure (B), note the initial position (12 o’clock) of
the CONTOUR control when the CONT switch is pushed. You
may observe the "indentation" in the receiver passband where the
Contour filter is placing a low-Q “notch” (per the setting of Menu
#078, referenced above). Counter-clockwise rotation (to the left) of
the Contour knob causes the indentation to move toward a lower
frequency within the passband, while clockwise rotation (to the right)
causes the indentation to move toward a higher frequency within
the passband. By removing interference or unwanted frequency com-
ponents on the incoming signal, it is possible to make the desired
signal rise out of the background noise/interference, enhancing in-
telligibility.