Page 56
FT-
991
Operating Manual
Interference Rejection
Digital NOTCH Filter
(
DNF
)
Operation
The Digital NOTCH Filter (DNF)
is an effective beat-canceling filter that can null out a number of interfering beat notes
inside the receiver passband. Because this is an Auto-Notch feature, there is no adjustment knob associated with this fil
-
ter.
Advice:
If a very strong interfering carrier is encountered, we recommend using the IF NOTCH filter first, as it is the most effec
-
tive notching tool in the receiver section.
1. Press the
F
(M-LIST)
button to show the functions
listed on the TFT display, then touch [
DNF
] on the
TFT display. The Digital NOTCH Filter will be set
to “
ON
”.
F(M-LIST) Button
Digital Noise Reduction
(
DNR
)
Operation
The Digital Noise Reduction (DNR) system is designed to reduce the level of ambient noise found on the HF and 50
MHz bands. The (DNR)
system is especially effective during SSB operation. While DNR is functioning, rotate the
MULTI
knob to adjust the DNR level. Any of 15 different noise-reduction algorithms can be selected; each of these al
-
gorithms was created to deal with a different noise profile. You will want to experiment with the DNR system to find the
best setting corresponding to the noise currently being experienced.
1. Press the
F
(MLIST)
button to reveal the functions
list on the TFT LCD display.
2. Touch [
DNR
] on the LCD. The DNR function will
be set to “
ON
”.
MULTI Knob
F(M-LIST) Button
DNR indicator
DNR level indicator
To disable the Digital NOTCH Filter, just repeat the
above procedure, touching [
DNF
] on the LCD to choose
“
OFF
”. The “
DNF
” will turn off, confirming that the
Digital NOTCH Filter is not active.
3. Rotate the
MULTI
knob to choose one of 15 algo-
rithms that best reduces the noise level.
4. To cancel the DNR filter, touch
[
DNR
] on the LCD,
“
OFF
” will appear in the display, confirming that the
DNR system is no longer in operation.