Yaesu FT DX 9000D - COMPUTER AIDED TRANSCEIVER, Operation Manual

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Page 76 FT
DX
9000D O
PERATION
M
ANUAL
SUB(VFO-B)
AGC switch
MAIN(VFO-A)
AGC switch
MAIN (VFO-A)
SUB (VFO-B)
SUB(VFO-B)
RX switch
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.
Main (VFO-A) Band AGC Selection
Rotate the Main (VFO-A) band’s AGC switch (# ) to
select the desired receiver-recovery time constant. For most
operation, we recommend the “AUTO” mode.
Sub (VFO-B) Band AGC Selection
1. Press the Sub (VFO-B) band’s RX switch (# ) to
engage Dual Receive operation.
2. Rotate the Sub (VFO-B) band’s AGC switch (# )
to select the desired receiver-recovery time constant.
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 selec-
tions are:
Operation Mode AUTO AGC Selection
LSB SLOW
USB SLOW
CW FAST
AM FAST
FM FAST
RTTY SLOW
PKT(FM) FAST
PKT(LSB) SLOW
Advice
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 amplifi-
ers and the following stages are probably being overloaded.
Quick 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.
T
OOLS FOR
C
OMFORTABLE AND
E
FFECTIVE
R
ECEPTION
Terminology
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 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.