Vertex Standard FT-2000 ユーザーズマニュアル
Page 54
FT-2000 O
PERATING
M
ANUAL
R.FLT (R
OOFING
F
ILTERS
)
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 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.
These filters provide protection fort 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.
I
NTERFERENCE
R
EJECTION (S
IGNALS
O
FF
F
REQUENCY
BY
J
UST
A
F
EW
KHZ
)
Press the [R.FLT] button to toggle the Roofing
Filter selection.
Filter selection.
AUTO
15 kHz 6 kHz 3 kHz AUTO
A
DVICE
:
The Roofing filter selection affects the Main band
(VFO-A) only. The Sub band’s (VFO-B) Roofing fil-
ter is fixed at a bandwidth of 15 kHz.
ter is fixed at a bandwidth of 15 kHz.
As you repeatedly press the [R.FLT] button, you will
observe changes in the notation in the R.FLT column
of the Receiver Configuration Indicator on the display,
denoting the
Roofing Fil-
ter currently
in use.
of the Receiver Configuration Indicator on the display,
denoting the
Roofing Fil-
ter 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
P
OINT
:
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 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:
15 kHz
LSB/USB/PKT:
6 kHz
CW/RTTY:
3 kHz
When the Roofing filter mode is set to “AUTO” and
the Noise Blanker is turned On, the Roofing Filter band-
width will automatically be set to 15 kHz, as this set-
ting provides the most effective noise blanking. How-
ever, you still may override the automatic setting, and
select a more narrow Roofing Filter. Noise blanking
may be compromised, however, with a tighter Roofing
Filter in the line.
width will automatically be set to 15 kHz, as this set-
ting provides the most effective noise blanking. How-
ever, you still may override the automatic setting, and
select a more narrow Roofing Filter. Noise blanking
may be compromised, however, with a tighter Roofing
Filter in the line.
T
ERMINOLOGY
:
A “Roofing Filter,” as its name implies, places a “Roof”
over the receiver’s IF system bandwidth. This “Roof” pro-
tects the circuitry downstream from the first mixer from
interference, just as a roof on a house protects the contents
from rain and snow.
over the receiver’s IF system bandwidth. This “Roof” pro-
tects the circuitry downstream from the first mixer from
interference, just as a roof on a house protects the contents
from rain and snow.
Receiver Configuration Indicator
[R.FLT] Button