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

I I I I I
NTERFERENCE NTERFERENCE NTERFERENCE
NTERFERENCE 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 to toggle the Roofing Fil-
ter selection.
AUTO 15 kHz
A
DVICE
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 inde-
pendently on each VFO in the VFO stack.
Q
UICK
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
FT 9000 C O
DX ONTEST
R R R R R
EJECTION ( S S S S S
EJECTION EJECTION
EJECTION EJECTION
ROOFING ( R
[ ROOFING ] Switch
6 kHz 3 kHz AUTO
P
OINT
15 kHz
6 kHz
3 kHz
M
PERATION ANUAL
O O O O O F F F F F
IGN IGN IGN IGNALS ALS ALS ALS FF FF FF FF FF REQUENCY REQ REQ
IGN ALS REQ REQ
)
F
OOFING ILTERS
LCD Display
Roofing Filter bandwidth
will be indicated
T
ERMINOLOGY
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.
J J J J J F F F F F
UENCY UENCY BY BY BY BY BY UENCY UST UST A A A A A UST EW EW EW EW EW KHZ KHZ KHZ KHZ
UENCY UST UST KHZ
VDD BIAS TEMP SWR
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