Interference Rejection; Roofing (Roofing Filters) - Yaesu FT DX 9000 CONTEST - MANUAL 2 Operation Manual

I
NTERFERENCE
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 for the 2nd mixer, DSP, and other circuitry that follow, 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.
Press the ROOFING switch (#
ing Filter selection.
AUTO 15 kHz
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.
Typically, this selection will be set to "AUTO."
The Roofing Filter selection will be memorized independently on
each VFO in the VFO stack.
Quick Point
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.
The AUTO mode Roofing Filter selections are shown
below:
AM/FM/FM-PKT
LSB/USB/PKT
CW/RTTY
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 9000 C
DX ONTEST
R
EJECTION
ROOFING ( R
) to toggle the Roof-
6 kHz 3 kHz AUTO
15 kHz
6 kHz
3 kHz
O M
PERATION ANUAL
(S O F
IGNALS FF REQUENCY BY
)
F
OOFING ILTERS
ROOFING switch
J F )
UST A EW KHZ
Roofing Filter bandwidth will be
indicated on the LCD
Roofing Filter bandwidth
will be indicated
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