Agc ( Automatic Gain Control ) - Yaesu FT dx 1200 Operating Manual

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The AGC system is designed to help compensate for fading and other propagation effects. The AGC characteristics can
be individually set for 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.
Press the [ AGC ] button repeatedly to select the desired
receiver-recovery time constant. You will observe the
AGC status notation in the AGC column of the Key
Function Display on the TFT display, denoting the AGC
receiver-recovery time currently in use. For most opera-
tions, we recommend the "AUTO" mode. Additionally,
you may disable the AGC by pressing and holding in the
[ AGC ] button for one second.
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ote
 The "AUTO" selection mode selects the optimum
receiver-recovery time for the reception mode.
In this case, the selected receiver-recovery time in
the AGC column of the Key Function Display glows
green (Normally glows blue).
 Pressing the [ AGC ] button allows selection of the
desired receiver-recovery time constant. Normally,
the "AUTO" selection is satisfactory for most situ-
ations, 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. The AUTO
mode selections are:
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perAting ode
LSB/USB/AM
CW/FM
RTTY/DATA
In traditional AGC systems, the audio output from the transceiver becomes essentially fixed once the threshold
for AGC action is reached (usually several dozen dB above the no-signal noise floor). The FT
includes an innovative Sloped AGC system on the Main band (VFO-A) receiver, that allows the audio volume
to rise and fall slightly according to signal strength. Although the rise/fall slope is not dramatic, it is sufficient to
allow you to use your ear to discern and separate signals according to signal strength, not just audio frequency.
Using Sloped AGC
1. Press the [ MENU ] button to engage the Menu mode.
2. Rotate the [ VFO-B/CLAR ] knob (or press the /
button) to select Menu item "004 AGC SLOPE".
3. Press the [ SELECT ] button, then rotate the [ VFO-B/
CLAR ] knob (or press the / button) to change the
setting to "SLOPE".
4. Press the [ SELECT ] button, then press the [ MENU ] but-
ton to lock in the new setting and exit to normal opera-
tion.You will now be using the Sloped AGC system.
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DX peraTing
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omfortable anD
Agc ( A
utoMAtic
Indicates the AGC
d
iSplAy
Auto Agc S
election
SLOW
FAST
MID
SLOPED AGC Operation
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anual
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ffective
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Ain ontrol
[ AGC ] Button
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 If the AGC receiver-recovery time is set
pressing and holding in the [ AGC ] button, 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.
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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
generally do not recommend any changes to the AGC
Menu selections until you are thoroughly familiar with
the performance of the FT
t :
erMinology
Automatic Gain Control, or AGC, is a circuit that senses
the received signal strength, and then limits the gain of
the RF and IF stages 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.
AGC start
Input Signal
r
eception
to "Off" by
1200.
DX
1200, however,
DX
SLOPED
NORMAL
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