Yaesu FT DX 9000D - COMPUTER AIDED TRANSCEIVER, Operation Manual

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Page 68 FT
DX
9000D O
PERATION
M
ANUAL
SUB(VFO-B)
CONT switch
MAIN(VFO-A)
CONT knob
MAIN(VFO-A)
CONT switch
SUB(VFO-B)
CONT knob
SUB(VFO-B)
RX switch
B
C
A
CONT
(
C
ONTOUR
)
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
)
Using Contour on the Main (VFO-A) Receiver
1. Press the Main (VFO-A) CONT switch (# ). The
LED imbedded in the switch will glow Red to con-
firm that the Contour filter is engaged.
2. Rotate the Main (VFO-A) CONT knob (# ) to
achieve the most natural-sounding audio reproduction
on the incoming signal. To cancel Contour tuning, press
the Main (VFO-A) CONT switch once more.
Using Contour on the Sub (VFO-B) Receiver
1. Pressing the Sub (VFO-B) band’s RX switch will
engage Dual Receive operation.
When the imbedded LED grows green, this is your
confirmation that Dual Receive is in operation.
2. Press the Sub (VFO-B) CONT switch (# ). The
LED imbedded in the switch will glow Orange, con-
firming that the Contour filter is engaged.
3. Rotate the Sub (VFO-B) CONT knob (# ) to
achieve the most natural-sounding audio reproduction
on the incoming signal. To cancel Contour tuning, press
the Sub (VFO-B) CONT switch once more.
Advice
The TFT’s Audio Scope (on the “Oscilloscope” page)
is particularly useful when adjusting the Contour con-
trol. Not only can you see the effect of the notch/peak
of the Contour system, but you also can see the posi-
tion of the notch/peak with respect to frequency com-
ponents of interest on the incoming signal. You may
then observe (on the Audio Scope) the effect of the
Contour control while listening to the effect on the
signal, and this will help build your intuition on how
best to use Contour tuning in the future.
The Width of the Contour filter effect, and the degree
of nulling or peaking, may be adjusted using the menu.
G
The Contour filter’s level (either nulling or peaking) may be
adjusted using Menu Item “RX DSP 078 MAIN-CONTOUR-
LEVEL” for Main (VFO-A) Band and “RX DSP 080 SUB-
CONTOUR-LEVEL” for Sub (VFO-B) Band. The factory de-
fault setting is –15.
G
The bandwidth over which the Contour filter effect is applied
may be adjusted using Menu Item “RX DSP 079 MAIN-CON-
TOUR-WIDTH” for Main (VFO-A) Band and “RX DSP 081
SUB-CONTOUR-WIDTH” for Sub (VFO-B) Band. The fac-
tory default setting is 10.
With reference to Figure (B), note the initial position (12 o’clock)
of the CONT 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
towered 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 components on the incoming signal, it is
possible to make the desired signal rise out of the background
noise/interference, enhancing intelligibility.
IF
BANDWIDTH
IF
BANDWIDTH
IF
BANDWIDTH
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.