Yaesu FT-847, Руководство по эксплуатации

Страница: 39 / 108

37
FT-847 O
PERATING
M
ANUAL
OPERATION
RF G
AIN
C
ONTROL
The R F G
AIN
control provides a
manual way to control the gain of the
receiver’s RF and IF amplifier stages.
For most operation, this control
should be left in the fully
clockwise
position, which provides maximum gain and best sen-
sitivity. However, under particularly noisy conditions,
net Signal-to-Noise Ratio may be improved by rotat-
ing the
RF
(G
AIN
) control counter-clockwise so that
the S-Meter reading holds a steady position slightly
higher than the (variable) S-Meter reading of the noise
itself. Signals weaker than this fixed S-Meter reading
may still be plainly audible, but they will no longer be
affecting the AGC system.
By doing this, you have
•
eliminated annoying noise
which does not contribute to effective reception, and
‚
created a new threshold for the onset of AGC ac-
tion, perhaps allowing even more effective action by
the DSP’s N
OISE
R
EDUCTION
, N
OTCH
, and/or the H
IGH
C
UT
/L
OW
C
UT
features (see pages 38, 40, 41).
When the noisy conditions have subsided, return the
RF (G
AIN
) control to its fully clockwise position.
IF N
OISE
B
LANKER
For reduction of impulse noise, such as that produced
by automotive ignition systems, the N
OISE
B
LANKER
fea-
ture may prove helpful. To activate the IF N
OISE
B
LANKER
:
•
Turn the Noise Blanker on by press-
ing the [
NB
] switch. The “
NB
” icon
will appear on the display, and you
should observe a reduction in the
ignition noise.
‚
To turn the Noise Blanker off, press
the [
NB ] switch again; the “
N B
”
icon will disappear from the display.
Note that the IF N
OISE
B
LANKER
may, under crowded
band conditions with extremely strong signals, cause
a slight degradation in overload immunity, or it may
create the sound usually associated with “splatter” on
a nearby signal (if that station is very strong). Try
switching off the N
OISE
B
LANKER
if you observe these
conditions.
R
ECEIVER
F
EATURES
C
LARIFIER
(R
ECEIVER
I
NCREMENTAL
T
UNING
)
The C
LARIFIER
provides a means of separating the re-
ceiver and transmitter frequencies by up to ±9.99 kHz.
This may be required for a number of situations:
l
If the station you are receiving should start to drift,
the C
LARIFIER
allows you to follow the drifting sig-
nal without requiring you to move your transmit
frequency.
l
In DX pile-up situations, the C
LARIFIER
offset capa-
bility may be sufficient to cover many “Split” call-
ing situations.
l
For VHF/UHF EME (“Moonbounce”) work, the
C
LARIFIER
allows you to set up a frequency differ-
ence corresponding to the predicted Doppler Shift
for the EME path. See “
Appendix ” beginning on
page 98 for more details regarding EME operation.
To utilize the C
LARIFIER
feature:
•
Press the [ CLAR ] switch; the
“
C L A R
” icon will appear on the
display.
‚
Rotate the SUB-TUNE control to
set the desired frequency offset for
the receiver relative to the transmit
frequency.
ƒ
To switch the C
LARIFIER
off, press the [
CLAR
]
switch once more.
Note : If you switch the C
LARIFIER
Off and do not touch
the
MAIN VFO
Tuning Dial, the contents of the
C
LARIFIER
’s register will be preserved. However,
if you change frequencies via the MAIN VFO
tuning Dial after turning the C
LARIFIER
Off, the
C
LARIFIER
’s register will be “cleared” to a zero
offset.