Yaesu FT-2000D, Руководство по эксплуатации

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Page 53 FT-2000D O
PERATING
M
ANUAL
The FT-2000D includes an unmatched array of RF selectivity-enhancing features. Please study the material below care-
fully, so as to understand the various features completely.
U
SING THE
VRF
(
V
ARIABLE
RF F
RONT
-
END
F
ILTER
)
The VRF system is a high-performance RF front-end preselector that has high Q factor and low insertion loss. VRF pro-
vides outstanding rejection of out-of-band signals, and can significantly improve reception in tough co-location operations
such as a contest or DX-pedition. The
FT-2000D
’s VRF system affects the 1.8 - 28 MHz amateur bands only.
A
DVANCED
I
NTERFERENCE
-S
UPPRESSION
F
EATURES
:
RF F
RONT
E
ND
1. Press the [
VRF
] button momentarily. The “
” icon
will appear at the FLT column of the Receiver Con-
figuration Indicator on the display, and the VRF sys-
tem will be
e n g a g e d ,
centered on
your current Amateur band.
2. You may rotate the [ VRF
] knob to skew the position
of the VRF system relative to your operating frequency.
Because the VRF system is relatively broad, although
still much narrower than the fixed bandpass filter), you
may not hear much difference in the background noise
or signal quality when you make minor adjustments.
However, if you have receiving problems associated
by a very strong signal, rotation of the [
VRF
] knob
may help reduce the strength of the interfering station,
allowing improved reception of the desired signal if
overload was degrading reception.
A
DVICE
:
ˆ You may observe the
relative skew of the
VRF system in the Tun-
ing Offset Indicator on
the display while turning
the [
VRF
] knob.
ˆ After moving the passband of the VRF system
manually, you may re-center it on the current Ama-
teur band by pressing and holding in the [
VRF
]
button for two seconds.
3. To switch VRF off, press the [
VRF
] button until the
“ ” icon shows “ ” in the FLT column of the
Receiver Configuration Indicator on the display; this
confirms that the VRF circuit has been removed from
the incoming received signal path.
Receiver Configuration Indicator
[VRF] Knob
[VRF] Button
A
DVICE
:::::
ˆ The VRF filter affects both the Main (VFO-A) and Sub
(VFO-B) bands.
ˆ The VRF Filter operational status will be memorized
independently on each VFO in the VFO stack.
Q
UICK
P
OINT
:
The VRF filter, utilizing high-quality coils and capacitors
that provide high Q, yields a passband that is approximately
20% to 30% the width of a traditional, fixed bandpass fil-
ter. As a result, significantly more “unwanted” signal re-
jection is provided. Within each Amateur band, the fol-
lowing adjustment steps are provided, if you wish to skew
the response in a particular direction so as to enhance in-
terference rejection even more. The actual “sound” of the
signal you are listening to will remain unchanged, how-
ever.
Offset Tuning Indicator
A
MATEUR
B
AND
1.8 MHz
3.5 MHz
5 MHz
7 MHz
10 MHz
14 MHz
18 MHz
21 MHz
24.5 MHz
28 MHz
VRF A
DJUSTMENT
S
TEPS
62 steps
62 steps
62 steps
62 steps
30 steps
30 steps
20 steps
20 steps
20 steps
20 steps