Interference Rejection; R.flt (Roofing Filters) - Yaesu FTDX9000D Operation Manual

Interference Rejection

Narrow-band Roofing Filters of 15 kHz, 6 kHz, and 3 kHz bandwidths are provided in the first IF, right after the first mixer.
These filters provide protection fort the 2nd mixer, DSP, and other circuitry that followm and can dramatically improve
reception on a very crowded band (during a contest, etc.). Typically, the AUTO selection mode is satisfactory for most
operating situations, but in an extremely crowded phone band you may wish to select, for example, the 3 kHz roofing filter
for SSB operation.
Main Band Roofing Filter Operation
Press the Main (VFO-A) band's R.FLT switch (#
to toggle the Roofing Filter selection.
AUTO © 15kHz © 6kHz © 3kHz © AUTO
H As you repeatedly press this switch, you will observe different
LEDs lighting up in the Roofing Filter area of the front panel,
denoting the Roofing Filter currently in use. Also, the selected
Roofing Filter bandwidth will be indicated on the TFT.
H Typically, this selection will be set to "AUTO."
H The Roofing Filter selection will be memorized independently
on each VFO in the VFO stack.
Sub (VFO-B) Band Roofing Filter Operation
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) band's R.FLT switch (#
to toggle the Roofing Filter selection.
AUTO © 15kHz © 6kHz © 3kHz © AUTO
H As you repeatedly press the RX switch (#
bandwidth will appear on the TFT.
H Typically, this selection will be set to "AUTO."
H When "AUTO" is selected, the LED imbedded in the switch
will go out (there always is a roofing filter in the receiver path).
H The Roofing Filter selection will be memorized independently
on each VFO in the VFO stack.
Quick Point
H The "AUTO" selection of the Roofing Filter is based
on the operating mode. However, you may override
the automatic selection, if band conditions warrant a
different (usually, a tighter) selection.
H The AUTO mode Roofing Filter selections are shown
below:
AM/FM/FM-PKT
LSB/USB/PKT
CW/RTTY
H When the Roofing filter mode is set to "AUTO" and
the Noise Blanker is turned On, the Roofing Filter
bandwidth will automatically be set to 15 kHz, as this
setting provides the most effective noise blanking.
However, you still may override the automatic set-
ting, and select a more narrow Roofing Filter. Noise
blanking may be compromised, however, with a tighter
Roofing Filter in the line.
Terminology
A "Roofing Filter," as its name implies, places a "Roof" over the receiver's IF system bandwidth. This "Roof" protects the
circuitry downstream from the first mixer from interference, just as a roof on a house protects the contents from rain and
snow.
FT 9000D O
DX PERATION
(Signals Off Frequency by Just a Few kHz)
R.FLT (R
OOFING
)
)
), the selected
15kHz
6kHz
3kHz
M
ANUAL
F )
ILTERS
MAIN(VFO-A)
R.FLT switch
SUB(VFO-B)
R.FLT switch
Roofing Filter
bandwidth will be
indicated on the TFT
Roofing Filter
bandwidth will be
indicated on the TFT
Roofing Filter bandwidth will be
indicated on the TFT
SUB(VFO-B)
RX switch
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