Moseley Associates RPL-4 User manual
www.SteamPoweredRadio.Com
I .
II.
III.
IV.
VI.
VII.
VIII.
IX.
x.
RPL-4
lNT~ODUCTION
SPECIFICATIONS
A.
Overall
System
B.
Transmitter
c~
R,eceiver
UNPACKING
TABLE
OF
CONTENTS
INITIAL
CHECK-OUT
P~OCEDURE
INSTALLATION
A.
Transmitter
B.
Receiver
c.
Antenna
and
Transmission
Line
OPERATION
A.
Transmitter
B.
Receiver
CIRCUIT
DESCRIPTION
A.
Transmitter
B.
Receiver
FIELD
ADJUSTMENTS
A.
Transmitter
B.
Receiver
SERVICING
OPTIONAL
MODEL
AMP-4
RF
POWER
AMPLIFIER
-i-
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1
2
2
2
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5
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14
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I.
INTRODUCTION
INSTRUCTION
MANUAL
MODEL
-
RPL-4
REMOTE
p·
rcKUP
:
LINK
The
Model
RPL-4
Remote
Pickup
Link
was
designed
to
provide
a
high-
quality
program
link
between
~he
broadcast
studio
and
an
outside
or
remote
broadcast
location.
Operating
in
the
450-470
MHz
band,
the
RPL-4
System
is
designed
for
two-channel
operation
with
the
second
set
of
crystals
optionally
available
.
The
RPL-4
consists
of
a
Transmitter
and
a
Receiver.
The
Transmitt
eL
was
designed
to
operate
continuously
from
120/240
VAC,
50-60
Hz
and
from
13.5
voe
negative
ground,
and
it
is
supplied
with
an
AC
power
cord
and
a
DC
cable
connector.
The
Transmitter
has
been
compactly
and
ruggedly
designed
to
facili-
tate
its
use
in
mobile
or
fixed
portable
service.
All
input
and
output
connectors
are
conveniently
located
near
the
front
panel
of
the
Transmitter
for
operator
convenience.
Easy
access
is
afforded
to
all
circuitry
du~
to
the
modular
design
of
the
system
.
Metering
of
important
parameters
is
provided
on
the
RPL-4
Trans-
mitter.
For
monitoring
audio
levels,
a .
PEAK
AUDIO
position
is
provided.
Metering
is
also
provided
for
relative
FORWARD
POWER,
relative
REFLECTED
POWER,
relative
I.P.A
DRIVE,
actual
FINAL
CURRENT,
and
POWER
SUPPLY
VOLTAGE.
For
applications
requiring
higher~
output,
the
Moseley
Associates
Model
AMP-4
may
be
used
in
conjunction
with
the
RPL-4
Transmitter.
The
Model
AMP-4
provides
a
5
dB
power
gain.
With
a
10-watt
input,
the
AMP-4
will
yield
32
watts
of
RF
output.
This
amplifier
is
not
recommended
in
aeronautical
service.
This
follows
the
policy
of
limiting
airborne
transmitter
power
output
to
18
watts.
The
Receiver
requires
only
1-3/4
inches
of
vertical
rack
space
.. To
assist
the
operator
in
optimizing
antenna
orientation
for
remote
pickup
broadcasts,
a
front-panel
signal-strength
meter
continuously
monitors
the
received
signal.
Selectors
are
provided
to
select
the
desired
frequency
channel
either
from
the
front
panel
or
from
a
remote
location
.
RPL-4
Rev.
3/ 78
-1-
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II,
SPECIFICATIONS
A.
OveralT
System
Audio
Response
Distortion
Signal-to-noise
ratio
Frequency
Range
B'.
Transmitter
±1.5
dB,
30-10,000
Hz
Less
than
1.3%,
30-10,000
Hz
55
dB
below
100%
modulation
(60
dB
typical)
450-470
MHz,
Two
Frequency
opera-
tion
within
2
MHz
spacing.
One
set
of
crystals
supplied
with
link.
RF
Output
13
watts
maximum,
10
watts
mini-
mum
into
50Q
load.
Output
connector
Typ
·e BNC
female.
VSWR
Protection
Deviation
Frequency
Stability
RPL-4A
Frequency
Group
No.
2
Group
No.
2
Channels
are:
450.0875
RPL-4
Rev.
4/78
450.1125
450.1875
450.2125
450.2875
450.3125
450.3875
450.4125
450.4875
450.5125
450.5875
450.6125
Withstands
infinite
VSWR
at
all
phase
angles.
RPL-4A
5
kHz
(7
.5
kHz
max
audio)
for
100%
modulation.
RPL-4B
10
kHz
(15
kHz
max
audio
as
appli-
cable)
optional
for
100%
mod
ulation.
±
0• 00025
% (-
30°
C
to
50°
C)
(MHz)
455.0875
455.1125
455.1875
455.2125
455.2875
455.3125
455.3875
455.4125
455.4875
455.5125
455.5875
455.6125
-2-
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R.PL-4B
Frequency
Group
Nl,
Rands
Group
No.
1
Channels
are
:
(MHz}
450
.'
050
455.050
450.150
455.150
450.250 455.250
450.350
455.350
450.450
455
.
450
450.550 455.550
Group
R
Channels
are:
(MHz}
450.650
455
,
650
450.700 455.700
450
.
750
455.750
450.800 455.800
450
.
850
455.850
Group
S
Channels
are:
(MHz)
450.925
455.925
Operating
Temperature
Range
-30°C
to
50°C
Audio
Inputs
3
independent
channels
(two
micro-
phone
and
one
line).
Audio
Input
Impecances
Line
so,ooo
n
bridging,
unbalanced
Microphone
S0-150n,
balanced,
floating
Audio
Input
Levels
Line
-15
dBm
to
+10
dBm
from
600
Q
sour
ce
Microphone
-60
dBm
to
-40
dBm
Audio
Peak
Limiter
Control
Range
greater
than
25
dB,
attack
time
1
ms,
release
time
700
ms
Metering
Audio
Monitoring
RPL-4
Rev.
4/
78
Peak
Audio,
Forward
RF
Power,
Re-
flected
RF
Power,
Final
Amp.
Current,
I 1P .A.
RF
Drive,
and
Power
Supply
Voltage
Utility
output
with
adjustable
gain
for
feeding
headphones
or
other
audio
amplifiers
.
-3-
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Power
Requirements
AC
DC
Size
Weight
C.
Receiver
Sensitivity
Selectivity
5 kHz
Deviation
10
kHz
Deviation
All
Spurious
Responses
Frequency
Stability
RF
Input
Audio
Output
Squelch
Operating
Temperature
Range
Power
Requirements
RPL-4
Rev.
4/78
120/240
VAC,
±15%,
50-60
Hz,
45
watts
t[JaximUill
13.5
VDC,
filtered,
negative
ground,
2.5A
·maximum;
15
VDC
maximum,
12
VDC
minimum.
4"
(10.2
cm)
high,
14.5"
(36.8
cm)
wide,
11"
(27.9
cm)
deep
16
pounds
net
(7.2
kg.
net)
1.5
microvolt
maximum
for
20 dB
quieting,
10
microvolts
maximum
for
40 dB SNR.
-6
dB@
±22
kHz
-60dB@
±42 kHz
•
-6
dB
@
±44 kHz
-60
dB@
±75 kHz
65
dB
below
-40
dBm
reference
±0.0005%
(-20°C
to
50°C)
son
unbalanced,
input
connector
Type
N
female
+10 dBm@
100%
modulation,
600Q
balanceq
Automatic
and
adjustable,
elec-
tronic.
Carrier-operated
relay
output
(Form C
contacts)
optionally
available.
-30°C
to
50°C.
120/240
VAC,
±15%,
50-60
Hz,
10
watts
-4-
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Size
Weight
1.-3/4
inche?
higll,
19
inches
wide,
10
'incpes
.
deep
· .(_4~5-
cm
x
48
.
cm
x
25
.
cm}
10
pounds
net
(4
15
kg.
net)
IIT.
·
...
. UNPACKING
The
RPL-4
Transmitter
and
Receiver
should
be
unpacked
and
carefully
inspected
for
concealed
damage
due
to
shipping.
Retain
all
boxes
and
packing
material
in
the
event
a
claim
is
to
be
filed
against
the
carrier
for
damages
.
NOTE
Do
not
attempt
an-y
tuning
at
this
time.
Field
Adjustment
Procedures
are
outlined
on
pages
12
and
13
of
this
manual.
Iv-.
·
INITIAL
CHECK-OUT
PROCEDURE
In
order
to
check
out
:
~he
equipment,
it
will
be
necessary
to
con-
nect
a
son
RF
termination
with
a
dissipation
rating
in
excess
of
15
watts
to
the
BNC
connector
on
the
rear
of
the
Transmitter.
Check
to
see
that
the
Transmit
Function
selector
is
in
the
STANDBY
position
and
that
the
PpWER
AUDIO
switch
is
not
depressed
.
Connect
the
line
cord
to
a
source
of
120
VAC,
50-60
Hz.·
Note:
For
240
VAC, _
50-60
Hz
operation,
refer
to
drawing
91C6667
for
information
on
rewiring
the
primary
of
transformer
Tl0l
.
Once
the
Transmitter
has
_been
properly
terminated,
depress
the
push
button
marked
POWER
AUDIO.
This
applies
power
to
the
audio
section,
multiplier/driver,
and
the
RF
power
amplifier.
Note,
however,
there
will
not
be
any
RF
output
at
this
time.
Place
the
Metering
Selector
in
the
FORWARD
POWER
position
and
select
the
proper
Trans-
mit
Function.
Either
FREQ
l
or
FREQ 2
may
be
selected
if
the
optional
set
of
crystals
for
dual
frequency
operqtion
has
been
in-
stalled.
If
the
system
is
set
up
for
single
frequency
operation,
FREQ
1
will
be
usea'.
Once
the
proper
Transmit
Function
has
been
depressed,
there
should
be
an
indication
on
the
front-panel
meter
which
is
a
reading
of
re-
lative
forward
power.
It
would
be
advisable
to
check
the
actual
power
output
with
a
wattmeter
to
become
familiar
with
the
relative
RPL-4
.
Rev.
4/78
-s-
www.SteamPoweredRadio.Com
meter
read;i,n~~ i.n
relat;i.o~
to
their
actual
yal
.
ue~
.
The
wattmeter
should
read
between
10
and
15
watts.
The
metering
functions
of
REFLECTED
POWER
~nd
I.P.A
,
DRIVE
are
also
relative
values
while
.
PEAK
AUDIO, FINAL
CURRENT,
and
POWER
SUPPLY
(Vee)
are
actual
read-
ings.
The
lower
scale
on
the
·
meter
is
used
for
two
readings;
FINAL
CURRENT
(0-2.5
amps)
and
Vee
(0-25
'VDC).
PEAK
AUDIO
in
dB
is
read
on
the
upper
scale.
Actual
values
may
be
·
compared
with
the
final
test
values
which
are
located
at
the
end
of
the
text
of
this
manual.
Variations
of
20%
may
be
expected.
Once
it
has
been
established
that
the
,
Transmitter
is
operating
properly,
place
the
Receiver
nearby
and
connect
it
to
the
120
VAC,
50-60
Hz
source.
Note
·
that
the
RPL-4
Receiver
does
not
have
a
power
switch.
The
L. E. D.
indicator
located
on
the
front
panel
will
illuminate
when
the
Receiver
is
connected
to
the
power
source.
For
240
VAC,
so~6o
Hz
operation,
see
drawing
91C6670.
A
small
piece
of
wire
should
be
inserted
into
the
Type
N
connector
located
on
the
rear
of
the
chassis
to
minimize
multipath
effects.
The
600Q
bal-
anced
output
of
the
-
Receiver
should
be
connected
to
a
monitor
·
amplifier
or
suitable
test
equipment.
If
specific
audio
measure-
ments
are
to
be
made,
the
Receiver
output
should
be
terminated
with
a
560~
resistor.
To
verify
the
operation
of
the
RPL-4
System,
apply
a +10
dBm
signal
at
700
Hz
to
the
Line
Input
of
the
Transmitter.
Adjust
the
Line
Input
Control
until
the
meter
on
·
the
Transmitter
reads
O
dB
with
the
Metering
Selector
in
the
PEAK
AUDIO
position.
If
the
Receiver
is
terminated
properly,
a +10
dBm
signal
should
be
present
at
the
output.
The
microphone
inputs
may
be
tested
at
this
time.
These
inputs
have
an
impedance
of
so-1son.
v.
INSTALLATION
· T'
ransmitter
The
Transmitter
may
be
operated
from
AC
and
DC
power
sources
. As
receiv~d
from
the
factory,
the
RPL-4
is
wired
for
both
120
VAC,
50-
60
Hz,
and
13.5
voe
operation.
Never
connect
both
AC
and
DC
inputs
at
the
same
time.
If
it
is
desired
to
operate
the
Transmitter
from
240
VAC,
50-60
Hz,
it
will
be
necessary
to
rewire
the
primary
of
transformer
Tl0l
as
shown
in
drawing
91C6667.
If
the
RPL-4
Trans-
mitter
is
to
be
operated
from
13.5
VDC,
connect
the
DC
source
using
the
cable
connector
pro
·
vided.
The
cable
connector
is
keyed
so
that
RPL-4
Rev.
3/80
-6-
www.SteamPoweredRadio.Com
it
can
.
be
connected
only
one
way;
how.eye~,
c~re
should
be
taken
when
connecting
the
DC
power
caple
to
.
the
cable
connector
to
insure
proper
polarity.
See
draw;i,ng 91C6667
for
proper
connection.
Diode
protection
has
been
provided
within
the
regulator,
and
in
the
event
the
polar;ity
is
acciq.entally
reversed,
the
Transmitter
will
blow
the
DC
fuse
..
CAUTT'ON
Do
not
connect
the
RPL-4
Transmitter
to
a
DC
source
greater
than
15
voe
as
damage
ta
the
unit
may
result.
When
the
Transmitter
is
to
be
used
in
a
fixed
location,
care
should
be
taken
to
provide
adequ~te
ventilation.
If
the
Transmitter
is
used
for
mob~le
-
operation,
it
may
be
desirable
to
fabricate
a
mounting
bracket.
Due
to
the
wide
variety
of
applications
and
vehicles,
no
mounting
bracket
is
supplied
or
a-vailable.
The
same
considerations
regarding
air
circulation
still
apply
in
mobile
operation.
B.
Receiver
The
Receiver
operates
from
120
VAC,
50-60
Hz.
If
it
is
desired
to
ope
.
rate
from
240
VAC,
it
will
be
necessary
to
rewire
the
primary
of
the
power
transformer;
see
drawing
91C6670
for
details.
If
remote
selection
of
the
frequency
channel
is
desired,
use
the
appropriate
barrier
terminals
on
the
rear
of
the
chassis.
A
SPOT
contact
configuration
is
required
for
this
function.
The
program
output
of
the
Receiver
is
available
from
the
same
barrier
strip.
c.
Antenna
and
Transmission
Line
Transmission
line
considerations
will
determine
to
some
extent
the
placement
of
the
Transmitter
and
Receiver
..
Lengthy
transmission
lines
will
introduce
unwanted
amounts
of
attenuation.
Therefore,
it
is
always
good
practice
to
place
both
the
Transmitter
and
Receiver
as
close
to
the
antenna
as
possible.
If
a
long
length
of
trans-
mission
line
is
required,
use
the
lowest
loss
line
practical.
There
are
many
possible
antenna
configurations
which
will
work
satisfactorily
with
the
RPL-4,
and
the
choice
should
be
determined
by
the
application
and
service
of
the
equipment.
The
internal
metering
of
the
RPL-4
may
be
used
to
help
match
the
antenna
to
the
RPL-4
.
Rev.
3/80
-7-
www.SteamPoweredRadio.Com
transmitter.
Observe
the
reflected
power
by
placing
the
Metering
Selector
in
the
RE;F'LECTED
POWER
position.
Tune
the
antenna
for
minimum
indication
on
the
meter,
consistent
with
max;i.mum
forward
power
.
It
should
not
be
necessary
to
adjust
the
Transmitter
as
it
has
been
factory
aligned
for
operation
into
a
son
load.
When
installing
the
antennas,
make
sure
that
both
the
transmitting
and
receiving
antennas
are
polarized
in
the
same
plane
.
vr.
·
OPERATION
A.
Tran
·
smi
tter
To
place
the
~RPL-4
Transmitter
into
operation,
check
to
see
that
the
POWER
AUDIO
switch
is
not
depressed
and
that
the
Transmit
Function
is
in
STANDBY.
Connect
the
AC
power
cord
to
· a
source
of
120
VAC,
50-60
Hz,
or
connect
a
DC
source
of
13
. 5
VDC
,
negative
ground,
to
the
DC
power
plug
located
on
the
rear
of
the
chassis.
Never
connect
both
AC
and
DC
inputs
at
the
same
time.
Due
to
the
wide
variety
of
mobile
installations,
no
DC
power
cable
is
pro-
vided.
However,
a
connector
is
provided
to
allow
for
the
fabrication
of
a
suitable
power
cable.
When
fabricating
this
cable,
be
certain
to
observe
the
correct
polarity,
and
select
the
proper
wire
size
to
avoid
excessive
voltage
drop.
Connect
all
audio
equipment
that
is
to
be
used
in
conjunction
with
the
RPL-4
to
the
Transmitter.
The
two
Microphone
Inputs
are
located
on
the
right
side
of
the
chassis,
while
the
Line
input
and
Utility
Output
jacks
are
·
located
on
the
left
side.
Connect
the
RF
trans-
mission
line
to
the
antenna
and
to
the
BNC
connector
located
on
the
rear
of
the
chassis.
Power
is
applied
to
the
audio
section,
multiplier/driver,
and
RF
power
amplifier
by
depressing
the
push
button
labeled
POWER
AUDIO.
However,
this
does
not
place
the
Transmitter
in
a
radiating
condi-
tion.
To
place
the
Transmitter
on
the
air
once
the
POWER
AUDIO
push
button
has
been
depressed,
simply
select
the
proper
Transmit
Function.
Either
FREQ
1
or
FREQ
2 may
be
selected
if
the
system
has
been
equipped
with
the
optional
set
of
crystals
for
dual
frequency
opera-
tion
. FREQ l
will
be
used
if
the
system
is
not
equipped
with
the
optional
crystals.
·
Relative
forward
power
,
as
well
as
other
metering
functions
, may
be
observed
by
selecting
the
appropriate
position
on
the
Metering
Selector
.
RPL-4
Rev.
3/80
-8-
www.SteamPoweredRadio.Com
With
the
POWER
AUDJ;O
push
button
depressed
and
the
Transmit
Func
-
tion
in
STANDBY,
·
the
audio
mixer
s.
ection
of
the
Transmitter
may
be
used
for
other
applications,
or
this
condition
may
be
used
t o
preset
audio
levels
before
placing
the
Transmitter
in
a
radiating
condition.
B
·.
·
Receiver
The
operation
of
the
RPL
- 4
Receiver
is
very
simple
since
there
ar
e
only
three
controls
f
or
the
operator's
use
;
the
rece
i
ver
frequency
se
l
ectors
labeled
FREQ
1
and
FREQ
2,
and
REMOTE
SELECT.
The
fre
-
quency
selectors
are
used
to
determine
on
which
channel
the
Rece
i
ver
will
operate.
The
REMOTE
SELECT
is
used
when
it
i s
de
-
sired
to
select
the
Receiver
frequency
channel
from
a
remote
location.
Barrier
terminals
have
been
pro
v
ided
on
the
rear
of
the
chassis
for
this
function.
An
SPOT
contact
configuration
is
re-
·
quired.
A
relative
signal
strength
meter
has
been
incorporated
into
the
Receiver
to
assist
in
the
setup
of
the
RPL-4
System
.
Also
incor-
porated
in
the
Receiver
is
a
provision
·
for
an
optional
carrier-
operated
relay
which
may
be
used
for
external
control
purposes
.
,-
VII.
CIRCUIT. DESCRIPTION
A.
Transmitter
The
transm
i
tter
is
comprised
of
f
ive
major
subassembLies
:
power
supply,
vcxo,
multiplier/dri
ver ,
RF
power
amplifier
,
and
audio
section
.
1.
Power
Supply
The
power
supply
regulator
ex
hibits
an
exceptionally
low
forward
voltage
drop
so
that
it
cannot
only
r
egulate
the
rectified
filtered
AC
input,
but
also
the
unregulated
12-15
voe
input
for
extremely
stable
RPL-4
operation
.
Ql02
biases
and
temperature
compensates
Ql04,
the
current
clamping
transistor.
Q103
is
a
current
driver
for
the
series
pass
transistor
Ql0l,
CRl0l,
CR102,
and
CR103
set
a
bias
on
the
voltage
regulator
ICl0l.
See
drawings
91B6908
and
20A2576.
RPL
- 4
Re
v.
3/80
-
9-
www.SteamPoweredRadio.Com
2.
Two-Channel
vcxo
In
order
to
generate
a
stable
sign~l
at
the
output
frequency
in
the
450-470
MHz
band
and
at
.
the
same
time
frequency-modulate
the
carrier,
a
VCXO
(voltage-controlled
crystal
oscillator)
is
used.
Ql,
Ll,Cl0,
Cll,
and
Yl
comprise
the
basic
4
MHz
oscillator
.
Fre-
qµency
multiplication
of
108
times
following
the
oscillator
produces
the
desired
output
frequency.
To
produce
frequency
modu-
lation
(refer
to
drawing
91C7164),
two
diodes,
CRl
and
CR2
which
change
capacity
as
a
function
of
voltage
.,
are
employed
in
the
oscillator
circuitry.
Temperature
compensation
is
achieved
by
application
.
of
DC
bias
to
the
modulator
diodes.
Thermistors
(temperature
variable
resistors)
Rl0
and
Rl2
and
a
resistor
net-
work,
(Rl5,
R9,
Rll,
Rl3, Rl4,
and
Rl8),
provide
the
necessary
corrective
bias
for
operation
over
the
specified
temperature
range.
The
Channel
1 VCXO,
Ql,
output
drives
emitter
follower
Q2
which
isolates
the
oscillator
circuitry
from
loading.
QS
is
used
as
an
OR
amplifier
and
.
passes
the
4 MHz
signal
from
·.
whichever
crystal
oscillator
is
operating.
Q6
is
a
current
amplifier
with
an
RF
output
of
approximately
0 dBm
into
50
ohms.
In
Channel
2
opera-
tion,
transistors
Q3
and
Q4
operate
in
·
the
same
manner
as
Ql
and
Q2
.
In
order
to
limit
the
RF
bandwidth
with
high
frequency
audio
a
three
section
audio
low
pass
filter,
Ul
,
limits
the
upper
audio
which
can
be
transmitted.
The
RPL-4
.'
A
is
limited
to
7.
5
kHz
and
the
RPL-4B
is
limited
to
15
kHz.
Multiplier/Driver
'
Transistor
Ql
is
a
frequency
tripler
followed
by
another
tripler,
Q2
_,
operating
with
output
frequencies
at
12.
5
to
13.
5 ·
and
37
. 5
to
40
MHz
respectively.
Tu~ed
circuits
(L2,
C4,
CB),
(L3,
Cl0,
Cll),
(L4,
Cl3,
Cl4),
(Ll0,
Cl6},
(LS,
CS,
Cl7}
and
(C6,
Cl9,
L6}
are
employed
to
remove
undesired
frequency
components
appearing
be-
cause
of
frequency
multiplication.
-
CR3,
C45, C46, C44,
Ll,
R21,
R22,
and
R23
are
part
of
a
phase
modulator
and
are
not
used
in
the
RPL-4
series
of
transmitter.
Tripler
Q3
multiplies
the
s i
gnal
to
112.5-120
MHz
~ith
(L7
,
C23,
C31)
and
(C25,
C40,
L8)
passing
only
the
desired
signal
to
Q4.
This
transistor
is
used
to
double
the
signal
to
225-240
MHz
~ith
(L9,
C28),
(L17,
C41)
and
(C29,
Z2}
used
to
remove
all
unwanted
signals
.
QS,
an
amplifier
with
the
output
RPL-4
Rev.
3/80
-10-
- I
www.SteamPoweredRadio.Com
at
225-240
MHz,
~nd
f;i,lter
(Ll3,
CSS,
C32,
ZS),
amplify
and
filte
r
the
~j,gn~l
}:)efore
it
;i,s
doubl.ed
i,n
the
~;i,nal
t~ansi~tor
Q6.
The
filter
(LlS,
C34),
lLll,
C38)
and
(Ll2,
C39)
is
triple-tuned
to
the
desired
output,
reducing
all
unwanted
signals
to
at
least
50
dB
lower
than
tlle
100
MW
·
nominal
450-470
MHz
desired
signal.
See
drawings
91C6900
and
20A2549.
RF·
Power
Amp'l'ifier
The
RF
power
amplifier
is
located
at
the
rear
of
the
chassis.
The
schematic
and
component
layout
can
be
seen
in
drawings
91B6864
and
20A2549.
The
approximately
100
milliwatts
of
RF
power
developed
in
the
·
Multiplier/Oriver
subassembly
is
applied
to
the
Power
Amplifier
subassembly
where
Q701,
Q702
and
Q703
amplify
the
450-470
MHz
signal
to
power
level
of
10
watts
nominal
into
50
ohms.
C702,
C701 ,
C703,
L701,
Z701,
and
R701
filter
and
match
the
50
ohm
input
signal
to
the
base
of
Q701.
C706,
C707,
L702,
Z703,
and
R709
match
and
filter
the
RF
signal
from
the
output
of
Q701
to
the
input
of
Q702.
C710, C711,
R702,
and
Z705
match
the
output
of
Q702
to
the
input
of
Q703.
The
output
of
Q703,
the
final
output
transistor,
is
matched
to
the
antenna
output
with
a
complex
matching
network
form
-
ed
by
L704, L705, L706,
L707,
C727,
C715
,
C716,
C717
and
C718.
This
highly
selective
multisection
filter
attenuates
all
unwanted
signals
to
at
least
60
dB
below
the
main
signal.
A
dual-
directional
coupler
samples
the
relative
forward
and
reflected
RF
powers
which
are
indicated
on
the
front-panel
meter.
The
overall
amplifier
efficiency
is
on
the
order
of
50
percent
• .
5.
Audio
s·
ection
The
audio
printed
circuit
board
is
located
directly
behind
the
front
panel.
Schematic
and
component
layout
can
be
seen
in
draw-
ings
91C6584
and
20A2356.
The
audio
sections
consists
of
three
major
subsections;
mixer,
limiter
amplifier,
and
peak
audio
limiter.
There
are
.
three
inputs
available;
two
50-lS0
n
balanced,
floating
microphone
inputs,
and
one
so,ooon
bridging,
unbalanced
line
input
.
These
inputs
a
re
combined
electronically
by
an
active
mixer,
IC2.
The
output
of
the
active
mixer
is
applied
to
the
limiter
amplifier,
IC3.
IC3
supplies
audio
to
the
utility
amplifier
and
the
phase
in-
v
erter
which,
in
turn,
feeds
the
meter
driver
and
peak
detector
.
RPL-4
Rev
. 3/
80
-11-
www.SteamPoweredRadio.Com
The
peak
audio
limiter
is
composed
of
a
solid-state
optical
attenu-
ator,
lirqiter
ampli~ie,r
IC3,
phase
inverter
:i;cs,
peak
detector
ICT,
and
buffer
amplifier
TCS.
This
limiter
has
an
attack
time
of
1
millisecond
and~
release
ti-me
of
700
milliseconds
with
a
typical
control
range
greater
than
25
dB.
The
utility
amplifier
output
is
an
unbalanced
600Q
with
an
output
of
O dBm,
which
can
be
used
to
drive
a
monitor
amplifier,
head-
phones,
tape
·
recorder,
or
telephone
line.
Adjustments
are
provided
for
Modulation
Level
(R35),
Utility
Level
(R27),
Meter
Calibration
(R47),
Meter
Zero
Adjust
(R66),
and
Meter
Acceleration
(R51}.
It
is
not
recommended
that
the
Meter
Accelera-
tion
be
adjus.ted
in
the
field
as
it
has
been
pre-adjusted
at
the
factory
for
optimum
response
and
should
require
no
further
adjust-
ment.
Pre-emphasis
is
standard
on
the
RPL-4
.
However,
if
it
is
desired
to
operate
the
system
without
pre-emphasis,
refer
to
drawings
9~C6584
and
20A2356
for
information
on
pre-emphasis
components
.
B.
Receiver
The
RPL-4
Receiver
is
a
superheterodyne,
dual-conversion
type
Re-
ceiver
employing
30
MHz
and
10.7
MHz
I.F.
frequencies.
The
Receiver
is
composed
of
nine
subassemblies;
preselector,
pre-
amplifier,
balanced
mixer/I.F.,
two-channel
local
oscillator,
30
MHz-10.7
MHz
converter,
crystal
bandpass
filter,
FM
demodulator,
audio
processor
and
power
supply.
The
schematic
for
the
Receiver
can
be
seen
in
drawing
91C6670.
(See
Figure
2
for
subassembly
lay-
out).
The
received
signal
is
applied
tq
the
three-section
helical
preselector
which
is
followed
by
a
low-noise
preamplifier.
Local
oscillator
injection
and
the
incoming
signal
are
applied
to
a
double
balanced
mixer
which
is
followed
by
a
30
MHz
bandpass
filter
and
amplifier.
This
resulting
signal
is
then
applied
to
the
second
converter
which
~onverts
the
30
MHz
signal
down
to
10.7
MHz.
The
output
of
this
converter
is
passed
through
a
10.7
MHz
crystal
band-
pass
filter
and
applied
to
the
FM
demodulator.
The
FM
demodulator
is
of
the
ratio
type,
and
included
in
the
demodulator
is
a
high
gain
RF
amplifier
limiter
IC.
The
output
of
the
demodulator
is
then
applied
to
the
audio
processor
where
it
undergoes
amplification
and
filtering
before
reaching
the
600~
balanced
output
of
the
receiver.
The
receiver
employs
a
variable
electronic
squelch.
The
squelch
level
is
adjusted
by
R6
on
the
audio
processor
board.
RPL-4
Rev
.
3/80
-12-
- 1
www.SteamPoweredRadio.Com
The
output
ot
the
~ece
.
iv
er
ma
y
pe
adjusted
from
its
nominal
+10 .dBm
output
at
100
.%
modulation
±3
c:U3Jll
PY
R26
on
t.lle
?lUd;i,o
processor
board
.
Also,
provisions
are
included
on
the
aud,io
pr
.
ocessor
boar
d
to
allow
for
the
addition
of
an::
a.ttenuator.
pad
to
provide
an
out
-
put
other
than
the
nominal
+10
dBm
.
De
-
emphasis
is
standard
on
the
RPL-4
Receiver
.
If
it
is
desired
to
run
the
system
f·
lat,
refe
r
to
draw
i
ng
91C6595
and
20A2367
for
information
on
de-emphasis
compo~ents
. ·
VI
I
I'.
.
FIELD"
ADJUSTMENTS
Complete
tuning
of
the
Transmitter
in
the
field
is
not
recommended
~
However
,
slight
frequency
adjustments
may
be
accomplished
by
ad-
justing
L2
for
Channel
1
and
L7
for
Channel
2.
B.
Receive
r
In
normal
operation
there
will
be
little
or
no
need
to
adjust
the
Receiver
in
the
field.
However,
ClOl
,
Cl02
and
Cl03
on
the
pre-
selector
may
be
adjusted
to
improve
Receiver
sensitivity.
Trimmer
capacitors
are
provided
within
the
two-channel
local
oscillator
to
allow
for
adjustment
of
the
oscillator
frequency.
Capacitor
Cl03
adjusts
the
Channel
1
frequency
,
and
Clll
adjusts
the
Channel
2
frequency
.
IX
. SERVICING
If
it
should
become
necessary
to
troubleshoot
the
RPL
- 4
System
,
complete
schematics
and
component
layout
di
a
grams·have
been
pro-
vided
and
are
located
at
the
rear
of
this
manual.
All
test
poin
t
voltages
are
shown
on
the
schematics
to
aid
in
localizing
any
problem.
Because
of
its
modular
design,
the
RPL-4
should
be
re-
latively
simple
to
troubleshoot
shoul
d
it
become
necessary.
If
factory
assistance
is
needed
,
please
note
all
pertinent
voltage
s ,
attempts
made
in
trying
to
locate
the
trouble,
and any
other
in-
formation
that
ma
y
be
helpful
in
diagnosing
the
problem.
Contact
Moseley
Associates,
Inc.
at
any
time
regarding
any
problem
encount
-
ered
with
the
RPL-4 .
Direct
any
inquiries
on
t he
operation
of
the
RPL-4
to
our
Customer
Service
Department
.
RPL.-4
Rev.
3/
80
-
13-
www.SteamPoweredRadio.Com
X.
OPTIONAL
MODEL
AMP-4
·
RF
.
POWER
,AMPLIFIER
When
it
is
felt
that
~dditional
output
from
the
RJ;>L-4
Transmitter
is
desired
for
extended
coverage
or
other
requirements,
the
Model
AMP.-4
RF
Power
Amplifier
-may
be
used
in
conjuncti,on
with
the
RPL-4
Trans~itter.
This
amplifier
provides
a
nominal
5 dB
power
gain,
and
with
a
10-watt
input
will
produce
an
output
near
35
watts.
Installation
of
the
AMP-4
is
straightforward
.
Considera-
tion
should
be
given
to
placement
·
of
the
amplifier
so
air
can
circulate
freely
by
the
heat
sink.
Further,
wiring
for
the
DC
supply
voltage
to
the
AMP-4
should
be
of
sufficient
size
to
pro-
vide
up
to
6
amperes
o-f
current
without
an
appreciable
voltage
drop
.
Voltage
requirements
are
13
. 5 VDC,
negative
grou~d
.
It
is
suggested
that
wire
of
equivalent
size
-
be
used
for
ground
return
to
a common
point.
In
a
vehicle,
do
no
rely
on
the
body
as
a
ground
return.
No
control
of
the
AMP-4
is
required
si~ce
only
negligible
current
is
drawn
only
with
the
presence
of
RF
input.
It
sho~~d
be
noted
that
the
AMP-4
is
Type
Accepted
for
use
with
the
RPL-4A & B
only,
although
it
will
work
with
other
equipment.
}U'L-4
·
Rey,
4/78
-14-
www.SteamPoweredRadio.Com
MOSELEY
ASSOCIATES
,
INC.
Date
6
Jan
.
1981
F ,0 .
No.
11-60
51
Tester
Conrad
Transmitter
Meter
Readings
TEST
DATA
MODEL
RPL-4
450
MHz
Cus
tomer
___
_,
KF
=-
R=C
___
_
Tx
Serial
No._""'3,.0.11,1;
8
.J.3.,_1
___
_
Rx
Serial
No.
_ _
3,..,N
2
_5,L:,
8~
--
-
Freque
ncy
455.75
0
MHz
2nd
F
req.
45
5.800
MHz
Receiver
Meter
Readings
Vee
11.5
16
.5
14
.5
µ.
Volts
SNR
Signal
Strength
IPA
Drive
Final
Current
2
amp
max
Forward
Power
3.
0
~
20
dB
Min
10
~
5
.~
6
.~
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Power
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1
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2•91
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2.87
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0,85
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