Yaesu FTdx5000MP, Руководство по эксплуатации

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Page 67 FT
DX
5000 O
PERATING
M
ANUAL
AGC
(
A
UTOMATIC
G
AIN
C
ONTROL
)
The AGC system is designed to help compensate for fading and other propagation effects, with characteristics that can be
of particular value on each operating mode. The basic objective of AGC is to maintain a constant audio output level once
a certain minimum threshold of signal strength is achieved.
VFO-A AGC Selection
Press the [ A
] button briefly to enable VFO-A (the LED
in the [
A
] button will glow red).
Move the [ AGC
] knob up or down to set the desired
receiver recovery time constant of the VFO-A receiver.
The selected recovery time will be indicated in the AGC
column of the Block Diagram Display.
Hold the [ AGC
] knob up or down for two seconds to
disable the AGC (for testing or weak-signal reception).
For most operations, we recommend using the “AUTO”
mode by pressing the [
AGC
] knob in briefly, or mov-
ing the [ AGC
] knob to set the ATT display to the
“AUTO” position.
VFO-B AGC Selection
Press the [ B
] button (the [
B
] button glows orange).
Move the [
AGC
] knob up and down to set the desired
receiver recovery time constant of the VFO-A receiver.
The selected recovery time will be indicated in the AGC
column of the Block Diagram Display.
Hold the [ AGC
] knob up or down for two seconds to
disable the AGC (for testing or weak-signal reception).
For most operations, we recommend using the “AUTO”
mode by pressing the [
AGC
] knob in briefly, or mov-
ing the [
AGC
] knob to set the ATT display to the
“AUTO” position.
T
OOLS FOR
C
OMFORTABLE AND
E
FFECTIVE
R
ECEPTION
N
OTE
:
When the AGC receiver recovery time is set to “OFF”,
the S-meter will no longer deflect. Additionally, you
will likely encounter distortion on stronger signals, as
the IF amplifiers and the following stages are prob-
ably being overloaded.
Normally, the AGC “AUTO” selection is satisfactory
for most situations, but in the event of operation on a
crowded band where you wish to receive a weak sig-
nal, you may change the setting (to “FAST”, for ex-
ample). The AGC “AUTO” mode selections are:
[A] Button
[AGC] Knob
[B] Button
[AGC] Knob
A
DVICE
:
When a received signal becomes degraded due to pulse
type noise, you may improve signal readability by setting
Menu items “
002 AGC FST HLD ”, “ 004 AGC MID
HLD
”, and “
006 AGC SLW HLD
” to “0 msec”.
Q
UICK POINT
Several aspects of AGC performance may be configured
via the Menu. However, because AGC can have such a
profound impact on overall receiver performance, we gen-
erally do not recommend any changes to the AGC Menu
selections until you are thoroughly familiar with the per-
formance of the
FT
DX
5000 .
T
ERMINOLOGY
:
Automatic Gain Control, or AGC, is a circuit that senses
the incoming signal strength, and then limits the gains of
the RF and IF stages, to maintain the output audio volume
at a more-or-less constant level. AGC also protects the
RF, IF, Audio, and DSP stages from overload, by limiting
the signal strength applied to circuits, regardless of the
input signal level.
O
PERATING
M
ODE
LSB
USB
CW
AM
FM
RTTY
PKT (FM)
PKT (LSB)
AUTO AGC S
ELECTION
SLOW
SLOW
FAST
FAST
FAST
SLOW
FAST
SLOW