Preamplifier/Mixer; Injection Amplifier; Image/Injection Filter - Motorola MSF 5000 Instruction Manual

MSF
5000
Instruction Manual
Chapter 1 Description
Preamplifier/Mixer
Injection Amplifier
Receiver Circuitry
The
preamplifier
mixer is
a
circuit board located between
the preselector
casing
and the casting of the
RF
Tray, next to the
image/injection
filters. The preamplifier
is
a
single
stage, common emitter amplifier. The received
RF
signal is passed
through the preamplifier. The output of
the
preamplifier is connected to the
image
filter before being passed onto
the mixer.
The mixer has
an
input port for the received
RF
signal and an input port for
the
Local Oscillator
(LO)
signal. The
LO
port is driven
by
the injection amplifier.
The
mixer is double-balanced
with
a
low
pass filtered output.
The output filter allows
the difference between the received
RF
signal and the
LO
signal
to
be applied to
the
I-F
amplifier.
The injection amplifier is located on the left-hand side of the
RF
Tray
between the
Receive
VCO
and the injection filters. The injection amplifier boosts the
VCO
output
to
sufficiently reduce mixer intermodulation products.
Image/injection Filter
68P81092E02
3/19/94
The image injection filter is
located
in
the front left-hand corner of the
RF
Tray.
The image filter portion is used
to filter the received
RF
signal between the
output
of the preamplifier and the mixer. The injection filter portion filters the
LO
signal
between the output of the injection amplifier and the mixer. Each of the filters
have tuning screws which extend through
the front of
the
RF
Tray casting.
1-65
MSF
5000
Instruction Manual
Chapter 1 Description
Preamplifier/Mixer
Injection Amplifier
Receiver Circuitry
The
preamplifier
mixer is
a
circuit board located between
the preselector
casing
and the casting of the
RF
Tray, next to the
image/injection
filters. The preamplifier
is
a
single
stage, common emitter amplifier. The received
RF
signal is passed
through the preamplifier. The output of
the
preamplifier is connected to the
image
filter before being passed onto
the mixer.
The mixer has
an
input port for the received
RF
signal and an input port for
the
Local Oscillator
(LO)
signal. The
LO
port is driven
by
the injection amplifier.
The
mixer is double-balanced
with
a
low
pass filtered output.
The output filter allows
the difference between the received
RF
signal and the
LO
signal
to
be applied to
the
I-F
amplifier.
The injection amplifier is located on the left-hand side of the
RF
Tray
between the
Receive
VCO
and the injection filters. The injection amplifier boosts the
VCO
output
to
sufficiently reduce mixer intermodulation products.
Image/injection Filter
68P81092E02
3/19/94
The image injection filter is
located
in
the front left-hand corner of the
RF
Tray.
The image filter portion is used
to filter the received
RF
signal between the
output
of the preamplifier and the mixer. The injection filter portion filters the
LO
signal
between the output of the injection amplifier and the mixer. Each of the filters
have tuning screws which extend through
the front of
the
RF
Tray casting.
1-65