Effective Reception; Agc (Automatic Gain Control) - Yaesu FT DX 9000 CONTEST Operation Manual

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.
Rotate the [ AGC ] switch to select the desired receiver-
recovery time constant. For most operation, we recom-
mend the "AUTO" mode.
Rotation of the [ AGC ] switch allows selection of the de-
sired receiver-recovery time constant. Normally, the
"AUTO" selection is satisfactory for most situations, but
in the event of operation on a crowded band where you
wish to receive a weak signal, you may wish to change
the setting (to FAST, for example). The AUTO mode se-
lections are:
O M AUTO AGC S
PERATING ODE
LSB
USB
CW
AM
FM
RTTY
RKT ( FM )
RKT ( LSB )
FT 9000 C O
DX ONTEST
T T T T T C C C C C
OOLS OOLS OOLS FOR FOR FOR FOR OMFOR OMFOR OMFOR T T T T T ABLE
OOLS OOLS FOR OMFOR OMFOR
AGC ( A
UTOMATIC
[ AGC ] Switch
ELECTION
SLOW
SLOW
FAST
FAST
FAST
RTTY
FAST
SLOW
M
PERATION ANUAL
E E E E E
ABLE AND ABLE ABLE AND AND AND FFECTIVE FFECTIVE FFECTIVE
ABLE AND FFECTIVE FFECTIVE
)
G C
AIN ONTROL
VDD
A
DVICE
If the [ AGC ] switch is set to the "Off" position,
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 probably being overloaded.
Q
UICK
Several aspects of AGC performance may be con-
figured via the Menu. However, because AGC can
have such a profound impact on overall receiver
performance, we generally do not recommend any
changes to the AGC Menu selections.
T
ERMINOLOGY
Automatic Gain Control, or AGC, is a circuit that
senses the incoming signal strength, and then lim-
its the gains of the RF and IF stages so as to keep
the output audio volume at a more-or-less constant
level. AGC also protects the RF, IF, Audio, and
DSP stages from overload, as it limits the signal
strength that is allowed to flow, irrespective of the
input signal level.
A A A A A
D D D D D VICE
When a received signal becomes degraded due to
pulse type noise, you may improve signal readabil-
ity by setting the AGC HOLD TIME in Menu
Items AGC 002, AGC 004, AGC 006, AGC 008,
AGC 010, and AGC 012 to "0 msec".
R R R R R
ECEPTION ECEPTION ECEPTION
ECEPTION ECEPTION
BIAS TEMP SWR
P
OINT
VICE VICE VICE VICE
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