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OCUBIC
COMMUNICATIONS
S"".IfI
DIVISION
"T"
L'"
)
ound.
CIIS and R12? shape the audio response.
When in the transmit condition, and when sending CW, the sidetone audio
signal is applied to the other input of UlO);
thus, the operator is able to
monitor his own sending.
CIIJ and Cl14 form an audio shaping network for more pleasing response,
and Cl12 couples the output to the speaker.
ClIO and Clll are RF bypasses.
CI09 bypasses
certain internal circuitry of
UIOJ, while RIJO and Cl15 pro-
vide a tYJ?e of feedback path known as "bootstrap" •
AUTOMATIC GAIN CONTROL
RIII
CI041
'='
C"107
""0
CIII05
QI04
A8C IVITrM
+8V
RIOI
AGe
SET
I'ROM CIOI
AI'
>-iHH-I
The audio frequency sig-
nal is coupled to the base of
QIOI
via ClOl.
Bias
is set
by RIOI,
RI02 and RIOJ, with
RIOI
serving as the AGC th-
reshold adjustment.
When the
audio peaks are of sufficient
amplitude, QJ.OI conducts, wh-
ich causes a
current to flow
through
RI05
and the D:l:!DAY
control,
a variabIe
resist-
anceto ground.
The
voltage
drop
across this combination
charges capacitor CI02,
with
series resistor RI06 control-
ling the
charging time,
and
thereby the attack time. When
the AF signal
disappears, C-
102 discharges through RI06 and the RI05-DECAY control combination, thus the
setting of the control varies thedecay time of the
AcC.
The voltage across CI02 is applied to the non-inverting input of ampli-
fier UlOlA.
Provided the output
of UlOIA
is greater than any reverse bias
to CRIOI supplied through
CRIOJ
by
the I.F. GAIN control,
the output of.U-
IOIA is applied to the AGC line
through CRI06,
and to the S meter through
calibration control RIIO and voltage dropping diodes CRI04 and CRI05.
RIO?,
RIOS and RI09 establish a reference level and the gain of UlOlA.
When in the transmit condition,
the "T" line goes high, and applies a
voltage through CRIOS to the inverting input of UlOlA, causing its output to
go low and remain there so long as the "T" line remains high, thus disabling
the amplifier.
This ensures that the S meter is disabled in transmit.
This
same voltage is applied, through CRIO?, to the AGC line to force maximum at-
tenuation of the AGC PIN diode in the IF amplifier chain, and to cut off the
I.F. integrated circuit amplifier, UIOl , on the exciter board.
This ensures
that no signal
is present in the AGC loop
during transmit and full gain is
available when switched back to receive.
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