Cubic SWAN SS-15 User Manual

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AGC/ALC
-
The
AGC/ALC circuits
are
used
to
develop
and apply
the
AGC and ALC
control
voltages.
The AGC
samples
the output
of
the
second
IF amplifier
and
develops
a negative
voltage which
is
used
to control
the
gain
of the
RF amplifier
and the
first IF
amplifier.
The
purpose of the AGC is
to
maintain
a
nearly
constant
audio
output
level
for
a wide
range
of signal
levels
and
to
preven
overloading
and
cross rnodulation
of
the RF
amplifier
ald
IF
1mp1i-
fier
due to
strong signals
received
at
the
antenna.
The RF
GAIN
control
is
located
in-the
AGC system
and it
controls the start
of
AGC action
by-
controLling
the
receiverts
maximum RF
gain.
Since
ALC
pertains to
the transnitter,
it
will
be
described
later
in
this section.
VFO
-
The
VFO
is
a
three
stage
osciLlator
anpLifier.
The basic
oscillator
is
a
dual
gate
MOSFET
q501
followed
by
a
FET
Q302
and
a bipolar
Q303
transistor
conbination
which
provides
high isola-
tion,
stability,
and
gain
1eveLi1g.
E19h
band
has
a separate
LC
circuit for
individual
barr-dspread
tracking
and temperature
compen-
sation.
The
VFO
frequency
is
5.5 MHz
lower
than
the;
received
frequency
on 20r
15 dnd 1'0 meters
and
5.5
MI{z
higher
on 40 and
80
meters.
i
PROD
DET
-
The product
detector
is essentiaLLy
a nixer-9!age.
It
mixes the
SSB
IF
signal
frequency
with
the
carrier
oscillator
frequency
(the
carrier
osciilator
is
described
later
in this
secdion)
.
-fne
resultant
difference
signal,
from the
sum
and
difference
nixing, is
the
audio
conponent
of the
received
signal.
The
signal
produ-ed from
the sum_nixing
is
an_RF
signal
and
it
is shuited
to
ground
and
not
used.
The transistor
used
for
the
product
detector
is
a
dual
gate
MOSFET
Q410.
CARRIER OSC
-
The carrier oscillator
is
a
crystal
controlled
osciLlator
amplifier
Ql07.
Two crystals
are
provided
for
the
control of
upler
and iower
sideband.
The 5.5
MHz
crystal
is
selected
by the
NORM
position of the
MODE
switch.
In this
position, th"
lower sideband
is
detected
or-generlt..$
on
80 and
?0
neteri
and
the
upper sideband
is
selected
on
20,
15
and 10
meters.
The
reason-ior
the
change
from
lower to
upper
sideband
is
the
change
from
sum
to
difference
mixing
in both
the
receiver
and
the
traismitter
mixer
stages.
The 5.5053
MHz
crystal
is
selected
by
the
OPP
position
of
the
MODE switch.
This
shifts
the carriei^
oscillatbr
to
the other
end
of
the
crystal
filter
causing a
reversal
of
the sideband
selected
from
that
noted
above.
This
oicillator
is also
used
in the
transnitter.
-
23-

Cubic SWAN SS-15 Specifications

General

Brand	Cubic
Model	SWAN SS-15
Category	Transceiver
Language	English