Contour Control Operation - Yaesu FT-991A Operating Manual

Interference Rejection
The Contour filter system provides a gentle perturbation of the IF filter passband. The Contour is set to either suppress,
or boost specific frequency components, and thus enhances the sound and readability of a received signal.
1. Press the F ( M-LIST ) button to display the function
menu list. Touch [ CONT ] to activate the CONTOUR
function and set the MULTI knob as the CONTOUR
adjustment knob.
2. Touch [ CONT ] on the TFT display. The Contour
function will be set to "ON".
CONT ( Contour ) indicator
CONT ( Contour ) level indicator
3. Rotate the MULTI knob to achieve the most natural
sounding audio reproduction of the incoming signal.
Advice:
 Rotate the MULTI knob to display the Contour
center frequency ( 10 Hz to 3,200 Hz ) below the
[ CONT ] indicator.
 The level indicator shows the amount of attenua-
tion for your reference.
4. To cancel Contour tuning, touch [ CONT ] on the
TFT display.
Advice:
 The Contour circuit operation will be set to "OFF".
 Touching [ CONT ] changes the Contour circuit op-
eration between "ON" and "OFF".
 The Contour function attenuation and bandwidth can
be set in Menu items "112 CONTOUR LEVEL" and
"113 CONTOUR WIDTH" ( refer to the instruction
on the right ) .
Quick Point:
By judicious use of the Contour filter, the "shoulder" of the passband response may be altered, or components may be
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.
Page 50

CONTOUR Control Operation

F ( M-LIST ) Button
MULTI Knob
Refer to Figure "B", this illustrates a "dip" in the
center of the Contour filter passband. The Con-
tour filter places a low-Q "notch" in the passband,
per the settings of Menu items "112 CONTOUR
LEVEL" and "113 CONTOUR WIDTH". Counter-
clockwise rotation of the MULTI knob causes the
notch to move toward a lower frequency within
the passband, while clockwise rotation causes the
notch to move toward a higher frequency within
the passband. By removing interference or un-
wanted frequency components of the incoming
signal, it is possible to make the desired signal
rise out of the background noise/interference, and
significantly enhance intelligibility.
A B
IF BANDWIDTH IF BANDWIDTH
MULTI MULTI
FT- 991 Operating Manual
C
IF BANDWIDTH
MULTI