VXR-5000
The CTC55 Tone
audio
level
output
is ad-
justed
by
VR2006
then
delivered to Q2002-3
and
the
transmitter line input.
Modulated
audio
from
the
Rx
unit
is deliv-
ered to
J2008-1
where
it
is fed
through
inti
ext
audio
select switch 52002 to Chebyshev Filter
Q2008-3 (NJM2902M)
and
then
high-pass fil-
tered
by
R2118
and
R2146. The
output
is then
delivered to five-section, active
HPF Q2008-1
which
rejects
audio
frequencies below 300
Hz. 3-pole active
LPF Q2006-3 rejects audio
frequencies above
3000 Hz.
Audio
is
de-emphasized
by
Q2006-2
(uPC4741G2)
and
R2043 & C2036, providing
flat
audio
response from 300
Hz
- 3 kHz. The
filtered
audio
then
passes
through
attenuator
52004
and
LINE
output
level potentiometer
VR2003
to
buffer
amplifier
Q2006-4
(uPC4741G2)
and
impedance
matching
transformer T2002 to LINE jack
J2001
pins 1
&2.
Repeater Operation
Duplex
Operation
The
demodulated
audio
is delivered from the
RX
unit
to Q2008
and
is high-pass filtered
and
de-emphasized as described above. Repeater
"sensitivity" is adjusted
using
VR2005 before
delivery to
Q2005 (uPC4741G2) via repeater
switch
52001-3.
When
the
repeater
mute
switch Q2001-4 is closed, the gain of Q2005 is
reduced
to
0,
effectively
muting
repeater
audio. Repeater
audio
deviation is controlled
by
potentiometer VR2004 before the signal
is
delivered to
audio
amplifier Q2003-4, where
the signal is processed
in
the
same
manner
as
previously described.
Intercom Function
Inserting a
standard
speaker I mic headset
into
the
INTERCOM jack 02010) provides
closed-loop
audio
for
test!
communications
with
an
installed remote base, for use
by
serv-
ice technicians. Inserting
the
headset
into the
jack disables
speaker
audio
via J2002,
pins
1
&
2.
Headset
microphone
audio
is delivered
to buffer amplifiers
Q2007-3
and
Q2007-4
(both NJM2902) before application to line
audio
selector Q2004.
2-4
Note!
If
using the optional YH-2
headset,
y~u
c~n
connect into either
the
line
or
Tx/Rx
ClrCUlts
for maintenance
or
testing.
Insert the
MIC/EAR
plug
of
the
YH-2 into
J2009
on
the CNTL-2 unit,
then
slide the IN-
TERCOM switch (S2003) to
the
desired
posi-
tion:
NOR -
normal
operation,
the
line is con-
nected to the
Tx/Rx
circuits.
TRCV - the YH-2 is connected
to
the
radio
Tx/Rx
circuits,
and
the
base
station
can
be
keyed
by
pressing the
blue
PTT
button
on
the
CNTL-l
Unit.
LINE - the YH-2 is connected
to
the line;
keying is
not
required.
Headset
level
is
adjusted
by
MON-LVL
(VR2007)
on
the CNTL-2 Unit.
The
default
setting
is
minimum
(fully
counter-clock-
wise). Note! -
remember
to set
the
switch
at
NOR for
normal
operation
when
the
YH-2
is
removed.
Power Supply
The
power
supply
includes
the
power
transformer
and
bridge
rectifier
D0002
(S25VB20)
on
the
chassis, a filter capacitor
bank
on
the
CAPA Unit,
and
various
regula-
tion
and
switching circuitry
on
the
REG Unit.
AC
power
is
applied
to
the
primary
of
TOOOI
through
fuse
FHOOOI
and
relay
RLOOOI.
The 16.5
VAC
at
the
secondary
is
then dual-fused
by
FH0002
and
FH0003 be-
fore delivery to full-wave
bridge
rectifier
D0002
and
the CAP A Unit.
The
output
of D0002 is
then
filtered
by
capacitor
bank
C8501
and
C8502
and
the re-
sulting DC is
applied
to
the
collectors of
Q7002
and
Q7004 (both
28018420)
on
the
REG
Unit,
and
regulator
Ie
Q70l3
(FMW1).
The control
output
of
Q7103 is
applied
to the
base of Q7007
(2SB1134R),
the
emitter
of
which
then
controls
the
bases
of
Q7002
and
Q7004,
thus
highly
regulating
the
voltages
at
the emitters. This
output
voltage is
then
de-
livered
through
relay RL7001 (FBR631 0012)
and
fuse FH7001
to
supply
the
13.5 VDC
bus
for
the
rest of
the
repeater. A
sample
of
the
13.5 VDC from
the
pass
transistors is also
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