POTOMAC INSTRUMENTS INC. AM-19 User manual
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TABLE
OF
CONTENTS
Paragraph
Page
1.1
1.2
1.3
2.1
3.1
3
.2
3.3
3.4
3.5
3.6
4.1
4.2
4.3
4.4
5
.1
5.2
5.3
6.1
6.2
6.3
6
.4
6.5
6.6
SECTION
1
GENERAL
DESCRIPTION
Scope
of
Manual
General
Description
Sununary
of
Specifications
SECTION
2
THF.oRY
OF
OPERATION
AM-19
Antenna Monitor
SECTION
3
INSTAIJ.,.ATION
AM-19
Inspection
Monitor
Configuration
Mounting and Power
Antenna Connections
Changing
Reference
Towers
Remote
Control
and
Auxiliary
Connections
SECTION
4
CALIBRATION
AND
OPERATION
AM-19
Calibration
Operation
Ll.ghtning and Overload
Protection
Remote
Control
SECTION
5
R»iOTE
METERING
PANEL
(s)
Installation
Calibration
Operation
SECTION
6
PRECISION
.ANTENNA
MONITOR
PM-19
(s)
Installation
Digital
Voltmeter
(DVM)
Calibration
Syrranetry Adjustments
Phase
Calibration
Sense
Current
Ratio
Calibration
i
1-1
1-1
1-5
2-1
3-1
3
-1
3-2
3-2
3-4
3-6
4-1
4-3
4-5
4-5
5-1
5
-2
5-2
6-1
6-2
6-2
6-3
6-4
6-4
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Paragraph
6.7
6.8
6.9
7.1
7.2
7.3
8
.1
8.2
8.3
9.1
9.2
9.3
9.4
9.5
9.6
9.7
9.8
10.1
TABLE
OF
CONTENTS
(continued)
Current
Deviation
Calibration
Overload and
Lightning
Protection
Remote
Control
and
Auxiliary Outputs
SECTION
7
DIGITAL
REMOTE
METERING
PANEL
RMP
-
19D
Installation
Calibration
Operation
SECTION
8
REMOTE
SWITCHING
ADAPTER
RSA
-1
9
(s)
Installation
Calibration
Operation
General
SECTION
9
MAINTENANCE
Trouble
Shooting
Power Supply
Relay
Replacement
Phasing
Capacitor
Adjustment -
Small
Phase
Errors
Servicing
Input
Modules
Replacing
Current
Detector
Diode
Digital
Voltmeter
SECTION
10
REPLACEABLE
PARTS
General
SECTION
11
SCHEMATIC
DIAGRAMS
SECT
ION
12
AM-19D(21O)
6-5
6-8
6-8
7-1
8
-1
8-2
8-2
9-1
9-1
9-2
9-2
9-2
9-3
9-3
9-3
10
-1
(s)
The
sections
of
this
manual which
deal
exclusively
with
the
details
of
a
particular
unit
are
included
as
supplements
when
the
units
are
specified
for
a
particular
installation.
ii
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Table
1-1
1-2
1-3
3-1
10-1
Figure
1-1
1-2
1-3
1-4
2-1
11
-1
11-2
11-3
11-4
11
- 5
11-6
11-7
11
-9
11-10
11-11
ll-12
11
-13
ll
-14
LIST
OF
TABLES
Summary
of
Outstanding
Features
Performance
Specifications,
AM
-
19
Antenna
Monitor
Performance
Specifications,
PM-19
Precision
Monitor
(AM
-
19
with
PMA-19)
AM
-
19
Interface
Connections
Index
of
Replaceable
Parts
LIST
OF
FIGURES
AM
-19 Antenna Monitor Photograph
PM
-
19
Precision
Monitor
(AM-19
with
PMA
-
19)
Photo
RMP
-
19
Remote Metering
Panel
Pho~ograph
RMP
-
19D
Digital
Remote
Metering
Panel
Photograph
Phase
Detector
Response
AM-19,
Simplified
Schematic Diagram
AM
-
19,
Main
Chassis
Schematic Diagram
AM
-
19
Input
Module, Schematic Diagram
Li.miter Module, Schematic Diagram
Phase
Detector
Module, Schematic Diagram
CUrrent Meter Module, Schematic Diagram
Power
Regulator
Module, Schematic Diagram
PMA
-
19,
Main
Chassis
Schematic Diagram
PMA-
19
Input
Module, Schematic Diagram
Current
Deviation
and
Switching
Module, Schematic
PMA-1.9, AnaJ.og
Buffer
Amp,
Schematic
Diagram
Remote
Metering
Panel,
RMP-19,
Schematic Diagram
Typical
Remote
Installation,
Functional
Diagram
iii
1-1
1- 5
1-6
3-S
10-1
1-3
1-3
1-4
1-4
2-3
11-2
11
- 3
11-4
11-5
11-6
11-7
11-S
11
-
10
11-ll
ll
-
12
ll
-
l.3
11-14
ll-15
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SECTION
1
GENER.AL
DESC
R
IPTION
1.1
Scope
of
Manual
This
instruction
manual
covers
the
theory
of
operation,
ins
t
allation
,
operation
and
maintenance
of
the
equipment
comprising
the
Type
19
Antenna
Monitor
System.
The Type 19 System
consists
of
the
following
major
rack-mounted
units
which
are
connected
in
various
combinations
depending
on
requirements:
Antenna
Monitor,
AM-19(2O4)
Precision
Monitor
Adapter,
PM.A-19
Remote
Metering
Panel,
RMP
-
19(204)
Digita
l Remote
Metering
Panel,
RMP-19D(21O)
Remote
Switching
Adapter,
RSA
-
19
The
sections
of
this
manual which
deal
exclus
i
vely
with
the
details
of
a
particular
unit
are
included
as
supplements
when
the
units
are
specified
for
a
particular
installation.
1.2
General
Description
'fype
19
System
1.2.1
Introduction
The Type 19 Antenna
Monitor
is
designed
to
accurately
measure
the
phase
relationships
and
sampling
loop
currents
within
the
directional
antenna
arrays
of
.AM
broadcast
stations.
The
Potomac
Instruments
system
offers
a number
of
unique
features
not
provided
in
previously
available
monitors.
These
features
are
summarized i n
table
1-1.
Table
1-1
Summary
of
Outstanding
Features
1 .
Superior
electrical
performance
with
solid
state
design
2.
Ul
tra
reliable
-
mercury
wetted
relays
and
mil
-
type
components
J.
Digital
display
of
all
three
precision
monitor
functions
4.
No
input
adjustments
-
rated
accuracy
over
full
range
of
input
level
5,
Non
seque
ncing
"touch"
operation
provid
ed
with
ligh
t
ed
pus
h
buttons
6.
Interference
filters
as
standard
feature
1-1
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7-
Overload
and
lightning
protection
8.
Remote
operation
with
se~ial
digital
and
BCD
output
for
printers
9.
Standard
configuration
up
to
12
towers
DA-3
10. Compact
building
block
system
design
1.2.2
AM
-
19(204)
The Antenna
Monitor,
Type
AM-19
is
the
basic
instrument
for
measuring
phase
and
loop
current,
and
provides
power and
most
of
the
control
functions
for
the
other
units
of
the
system.
The
standard
AM-19
is
designed
to
monitor
up
to
12
towers
and
can
acconnnodate
DA
-1 (DA-N), DA-2,
and
DA
-3
antenna
patterns.
The
unit
includes
two
precision
meters
for
a
simultaneous
indication
of
phase
and
current
ratio.
The
phase
meter
is
ca
librated
in
degrees
and
ind
i
cates
the
phase
difference
between
any
selected
tower
and
the
reference
tower
corresponding
to
the
pattern
in
use.
The
phase
meter
accuracy
is±
1.0
degrees
with
a
resolu-
tion
of
0.5
degrees.
The
current
ratio
meter
is
calibrated
in
percent
of
the
reference
tower
loop
current
for
any
se
l
ected
tower.
The
current
ratio
meter
accuracy
is±
1.5
percent
with
a
resolution
of
0.5
percent.
For
many
applications,
the
AM-19
is
the
only
Type
19
unit
required.
1.2.J
PMA
-
19
Many
of
the
more
critical
antenna
arrays
require
phase
and
current
re-
solutions
of
0.1
degree
and
0.1
percent
respectively.
To
obtain
this
performance,
the
AM-19
is
connected
with
the
Precision
Monitor
Adapter,
Type
PMA
-
19.
This
unit
includes
a
digital
voltmeter
and
the
critical
circuitry
and
controls
asso-
ciated
with
the
current
deciation
mode,
and
provides
a 4
digit
L.E.D.display
of
phase,
current
ratio,
and
current
deviation.
Basically,
the
current
deviation
circuit
consists
of
two
current
detectors,
one
connected
to
the
reference
tower
sampling
line,
the
other
to
a
selected
tower,
with
the
detector
outputs
connected
differentially
to
the
digital
voltmeter.
Attenuators
are
provided
to
normalize
the
input
l
evel
from
each
sampling
line
for
a
differential
voltmeter
indication
of
000.0. The
circuit
constants
are
de-
signed
so
that
any
variation
of
the
sampling
line
input
level
is
indicated
direct-
ly
on
the
DVM
in
percent
of
the
normalized
ratio.
The
"differential"
approach
to
this
measurement
allows
current
ratio
variations
to
be
determined
with
a
resolution
of
0.1
percent,
even
in
the
presence
of
large
carrier
level
variation
due
to
asymmetrical
modulation
and
other
causes.
The
standard
PMA-19
will
accom-
modate
up
to
12
towers
in
a
DA-1
or
DA-2
pattern,
and
up
to
6
towers
in
a
DA-3
pattern.
The
AM-19
and
PMA
-
19
units
can
be
specified
together
as
the
Type
PM-19
Precision
Monitor
.
1.2.4
RMP-19(204)
In
remote
control
installations
of
the
AM.-19
Antenna
Monitor,
the
Remote
Metering
Panel
Type
RMP
-
19
is
provided
at
the
studio
to
directly
monitor
phase
and
loop
current.
The
RMP-19
meter
physically
duplicates
the
meters
in
the
l-2
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AM-19
and prov.ides
the
same
specified
accuracy
and
resolution.
A
relay
mounted
behind
the
meter
panel
allows
selection
of
either
meter
directly
from
the
studio
remote
control
unit
as
the
phase
angle
and
loop
current
functions
are
"dialed
up".
Calibration
controls
for
the
RMP-19
are
included
in
the
AM-19
and
the
system
is
designed
to
provide
specified
accuracy
over
lines
with
up
to
ll,000
ohms
resistance.
1.2.5
RMP-19D(210)
The
Digital
Remote
Metering
Pan~l
RMP-19D
is
designed
to
prov.i.de a 4
digit
L.E.D.
display
of
the
functional
outputs
of
the
AM-19
and
the
PM-19
Antenna
Monitors.
When
used
locaD.y
with
the
AM-19,
the
RMP-19D
prov.ides
a
greatly
im-
proved
phase
resolution
of
0.1
degree,
and
the
digital
readout
significantly
reduces
the
possibility
of
operator
error
in
recording
phase
and
current
ratio
readings.
However, because
of
normal
carrier
level
fluctuations,
the
RMP-19D
is
not
a
substitute
for
the
PMA-19
in
providing
a
loop
current
resolution
of
0,1
percent.
The
RMP-19D(210)
can
also
be
substituted
for
the
RMP-19
Remote
Metering
Panel
as
the
studio
indicating
device
in
remote
control
installations
of
the
AM-19
and
PM-19
monitors.
Remote
operation
of
the
Type
19
System
requires
that
the
tower
and
mode
selector
relays
be
energized
from
the
transmitter
remote
control
unit.
In
some
systems
the
"raise-lower"
control
circuits
do
not
utilize
voltages
which
are
compatible
with
the
Type
19
monitor,
and
in
these
installations
the
Remote
Switching
Adapter Type
RSA-19
will
be
required.
This
unit
provides
all
the
necessary
relays
with
correct
coil
voltage
and
contacts
to
properly
interface
the
Type
19
monitor
with
the
remote
control
equipment. Power
for
the
RSA-19
is
provided
from
the
AM-19.
Because
of
the
diversity
of
remote
control
systems
used
for
broadcast
applications,
the
Remote
Switching
Adaptors
are
custom
designed
for
each
installation
.
1,3
Swmnary:
of
Specifications
Table
1-2
Frequency Range:
Performance
Specifications,
AM
-1
9 Antenna Monitor
150
KHz
to
2000
KHz
Phase Angle Range:_
Phase
Accuracy:
Phase
Resolution:
Current
Ratio
Accuracy:
Current
Ratio
Resolution:
0
to
180
degrees,
lead
or
lag
+
,_
1.0
degree
0,5
degree
±
1,0%
(20%
to
110%)
0,5%
1-5
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Table
1-2
Performance
Specifications,
AM-19
Antenna Monitor
(continued)
Metering
Tracking
Accuracy:
Available
Patterns:
Maximum
Towers:
RF
Input
Impedance:
RF
Input
Level:
Minimum
Input
for
100%
Current
Reference:
Relay
Voltage:
Power:
D:iJnensions, 19
inch
rack
mounting:
+ 0.5%
DA-1
(or
DA-N),
DA-2,
DA-3
12
50
or
72
ohms
(other
impedances on
special
order)
0.5
to
20
volts
rms
2.0
volts
rms
-24
volts
DC
nominal
105
to
130
volts
AC,
50-60
Hz
approximately
56
watts
(80
watts
with
PMA-19)
7
inches
high
x
12
3i4
inches
deep
behind
front
panel
.................'............
Table
1-3
Performance
Sp
ecifications,
PM-19
Precision
Monitor
(AM-19
with
PMA-19)
Frequency Range:
Phase Angle Range:
Phase Accuracy:
Poase
Resolution:
Current
Ratio
Accuracy:
Current
Deviation
Range:
Current
Deviation
Resolution:
Available
Patterns:
Maximum
Towers:
RF
Input
Impedance:
500
KHz
to
2000
KHz
0
to
180
degrees,
lead
or
lag
±
1.0
degree
0.1
degree
!
LO%
{20%
to
ll.0%)
±
25%
0.
1%
DA-1
(DA-N),
DA-2,
DA-3
12
with
DA-1
and
DA-2
patterns
6
with
DA-3
pattern
50
or
72 ohms
(other
impedances on
special
order)
1-6
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Table
1-3
Performance
Specifications,
PM-19
Monitor
(continued)
RF
Input
Level
Minimum
Input
for
100%
Current
Reference
Power:
Dimensions,
19
inch
rack
mounting
0.5
to
20
volts
rms
2.0
volts
rms
Power
is
obtained
from
the
.AM-19
AM-19:
PMA-19:
1-7
7
inches
high
x 12
3/4
inches
deep
7
inches
high
x 15
3/4
inches
deep
behind
front
panel
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SECTION
2
THEORY
OF
OPERATION
2.1
AM-19
Antenna
Monitor
Figure
11-1
is
an
overall
simplified
schematic
diagram
of
the
.AM-19.
The
AM-19
Main
Chassis
schematic
diagram
is
shown
in
figure
11-2.
2.1.1
Input
Module
Figure
11-3
is
a
schematic
diagram
of
the
AM-19
Input
Module, however,
figure
11-1
may
be more
useful
for
understanding
its
operation.
In
the
AM-19
space
is
provided
for
a
maxi.mum
of
twelve
Input
Modules.
These modules
contain
the
coaxial
input
receptacle,
termination
resistance,
and
tower
and
pattern
selection
relays,
and
are
installed
according
to
the
requirements
of
the
individual
installation,
as
are
the
pattern
and
tower
selector
push
buttons.
Special
Input
Modules
are
provided
for
the
reference
sampling
lines.
There
are
no components
which
are
dependent
on
the
operating
frequency.
One
Input
Module
is
supplied
for
each
tower
in
the
system.
Each
Input
Module
contains
relay
KJ.
Relays
Kl
and
K2
are
included
only
on
those
Input
Modules
used
in
conjunction
with
a
reference
tower
.
Relay
K3
is
the
two-
pole
tower
selection
relay.
One
pole
connects
the
tower
to
the
current
detector.
The
second
pole
connects
the
tower
to
the
selected
tower
limiter.
This
relay
is
energized
by
the
front
panel
tower
se-
lector
push
button.
Pressing
the
push
button
connects
Input
Module
terminal
5
to
the
+24
volt
connnon,
energizing
SCR2,
which
in
turn
closes
K3.
When
the
AM
-
19
is
used
with
the
PMA-19
Precision
Monitor
Adapter,
SCR-2
also
energizes
the
associated
tower
relay
in
the
PMA-19.
Terminal
13 on
the
Input
Module
is
connected
to
terminal
13 on
all
other
Input
Modules.
This
is
the
selected
tower
release
buss.
Energizing
any
relay
produces
a
negative
pulse
on
the
release
buss
which
extinguishes
SCR2
in
the
other
modules
and
disconnects
all
other
towers.
In
addition
to
this
feature,
the
+24
volt
common
is
connected
in
series
through
the
selector
switches,
which
insures
that
no two
towers
can
be
selected
simultaneously.
Pressing
the
DAY
front
panel
push
button
energizes
relays
Kl
and
K2
on
the
reference
Input
Module
associated
with
the
Day
reference
tower.
The
contacts
of
relay
K2
apply
the
signal
from
this
tower
to
the
reference
limiter.
The
contacts
of
Kl
connect
the
DAY
potentiometer
to
the
Current
Meter
Module.
The
current
detector
consists
of
Cl,
CR3
and
Rll.
It
is
located
on
the
last
non-reference
Input
Module.
In
those
installations
where
the
reference
tower
is
the
same
for
both
day
and
night
operation,
the
unit
will
st
ill
contain
two
reference
Input
Modules.
This
is
necessary
to
switch
the
DAY
and
NIGHT
REFERENCE
LEVEL
po-
tentiometers
to
acconnnodate
the
different
current
levels
in
day
and
night
operation.
In
this
case,
a jumper
is
connected
from
terminal
2
of
the
Day
2-l
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reference
module
to
terminal
2
of
the
Night
reference
module.
Also,
the
connec-
tion
is
removed from
terminal
7
of
the
Night
reference
module. These changes
allow
alternate
selection
of
the
DAY
and
NIGHT
potentiometer
by
the
DAY
and
NIGHT
MODE
push
buttons,
and
at
the
same
time
keep
relay
K2
in
the
DAY
reference
module
in
the
energized
condition
in
both
the
DAY
and
NIGHT
modes.
2.1.2
Limiter
Module
The
limiter
Module
schematic
diagram
is
shown
in
figure
11-4.
The
AM
-19
contains
two
identical
Ll..miter Modules, one
for
the
reference
tower
channel
and
one
for
the
selected
tower
channel.
F.a.ch
module
accepts
the
sinusoidal
RF
input
and
"hard
limits"
the
signal
to
an
approximate
square
wave
with
we
ll
defined
zero-axis
crossings.
This
high
degree
of
limiting
is
main-
tained
in
the
presence
of
deep
modulation
with
input
levels
down
to
0 .5
volts
rms.
Limiting
is
accomplished
by
two
integrated
circuit
differential
clippers.
Within
the
Lilniter
all
coupling
is
DC
and
both
phases
of
the
differential
outputs
are
used
.
Emitter
followers
are
used
for
coupling
between
the
differential
ampli-
fiers
and
between
the
Lilniter
output
and
the
Phase
Detector
Module.
Zener
diode
CR4
effectively
reduces
the
DC
level
at
the
collector
of
Al
and
allows
DC
coupling
through
the
emitter
followers
and
into
the
next
limiting
stage.
The
technique
of
differentially
driving
the
second
limiting
stage
provides
well
defined
zero
axis
crossings
with
sharp
rise
time.
The
peaking
action
of
coils
L1 and
I2
further
improve
the
rise
time.
Potentiometer
RlO
and
the
calibration
panel
SYMmetry
potentiometer
are
related
adjustments
which
are
used
to
balance
the
first
differential
amplifier.
RlO
is
factory
set
and
is
not
normally
readjusted.
However,
if
required
(because
of
card
replacement
or
repair)
readjustment
of
RlO
is
a
simple
matter,
and
is
performed
with
no
input
to
the
unit.
The
related
SYMmetry
potentiometer
is
initially
set
to
its
mid-range
and
RlO
is
set
for
a O
volt
difference
between
TPl
and
TP2
.
Final
symmetry
adjustments
are
covered
in
Section
4,
par.
4.1.2.
2 .
1.3
Sense
Circuit
The
sense
circuit
provides
a means
of
determining
whether
the
selected
tower
phase
is
leading
or
lagging
the
reference
tower
phase.
The
sense
circuit
which
is
included
in
the
Limiter
Module
consists
of
R32,
C9,
14,
CR3,
R31, and C8.
Basically,
the
sense
circuit
functions
by
inserting
a
small
additional
phase
shift
in
the
input
to
the
reference
tower
limiter.
The
circuit
is
actuated
by
pressing
the
SENSE
push
button
switch
on
the
calibration
sub-panel
which
ap
-
plies
a
forward
bias
to
diode
CRJ. The
conduction
of
CR3
effectively
shunts
the
limiter
input
with
the
impedance
of
C8
and
RJl,
and
causes
a
phase
delay
in
the
reference
signal.
Having
the
resistor
in
series
with
CB
maintains
a
uniform
phase
shift
of
approximately
4
degrees
over
the
specified
frequency
range.
The
other
components
in
the
circuit
determine
the
proper
diode
current
and
provide
RF
isolation.
Releasing
the
SENSE
push
button
returns
a
high
reverse
bias
to
the
low
capacity
diode
CR3,
and
isolates
the
phase
shifting
components from
the
2-2
www.SteamPoweredRadio.Com
limiter
input.
The
sense
circuit
in
the
selected
tower
Limiter
is
not
used
a
nd
the
Main
Chassis
is
wired
to
provide
a permanent
reverse
bias
to
the
switching
diode.
The
sense
indication
is
more
easily
interpreted
with
the
aid
of
figure
2-1
which
is
a
representation
of
the
phase
detector
response.
The
phase
detector
generates
a
DC
voltage
which
is
linearly
proportional
to
the
phase
angle,
with
the
function
increasing
from
Oto
180
degrees,
and
decreasing
back
to
a
reading
of
O from 180
to
360
degrees.
For
angles
greater
than
180
degrees
the
PHASE
.ANGLE
meter
reading
equals
360
degrees
minus
the
angle.
For
example, 270
degrees
will
produce
a
meter
reading
of
360-270 =
90
degrees,
and
the
same
meter
reading
is
obtained
for
a
leading
or
lagging
angle
of
10
and
350
degrees,
100
and
260
degrees,
176 and 1
84
degrees,
etc.
If
the
selected
tower
phase
leads
(positive
angle)
the
reference
tower
phase
by
some
angle
from
Oto
approxi.rnately 176
degrees,
pressing
the
SENSE
push
button
will
effect
an
additiona
l
reference
phase
delay
of
about
4
degrees
caus-
ing
the
meter
reading
to
increase
by
that
amount.
If
the
selected
tower
phase
leads
the
reference
tower
phase
by
some
angle
from
180
degrees
to
approxi.rnately
356
degrees,
the
meter
indication
will
equal
360
-
angle
-
4°,
and
pressing
the
SENSE
push
button
will
cause
the
meter
to
decrease.
When
a
leading
phase
angle
is
appro.x:i.mately 4
degrees
less
than
.180
degrees
or
360
degrees,
the
sense
indication
must
be
interpreted
carefully
since
the
meter
reading
may
11
go
through
11
180
degrees
or
360
degrees
(0
degrees
on
the
meter).
For
example,
if
a
selected
tower
phase
leads
the
reference
tower
phase
by
179
degrees,
pressing
the
SENSE
push
button
will
increase
the
phase
to
approxi.rnately
183
degrees
which
produces
a
meter
reading
of
360-183 = 177
degrees
-
thus
the
meter
reading
will
decrease
which
might
be
erroneously
interpreted
as
a
lagging
phase
ang
l
e.
If
the
selected
tower
phase
lags
(negative
angle)
the
reference
tower
phase,
the
PHASE
ANGLE
meter
will
read
the
same
as
for
a
leading
angle
but
the
sense
indication
will
be
reversed.
Thus
pressing
the
SENSE
push
button
will
cause
the
phase
reading
to
decrease
for
lagging
angles
from
approx:i.ma.tely 4
degrees
to
180
degrees,
and
increase
for
lagging
angles
.from
approximately
184
degrees
to
360
degrees.
Again,
the
sense
indication
for
angles
within
approxi-
mately
4
degrees
of
O
or
180
degrees
must
be
interpreted
carefully.
180°
PHASE
METER
READING
-180°
(LAG)
PHASE
ANGLE
+180°
Figure
2-1
.
Phase
Detector
Response
(LEAD)
www.SteamPoweredRadio.Com
The
sense
ambiguities
for
phase
angles
near
O
or
180
degrees
can
be
eliminated
by
inserting
an
additional
length
of
coaxial
cable
in
the
sampling
lines
from
the
towers
in
question.
2.l,4
Phase
Detector
Module
The
Phase
Detector
schemati c
diagram
is
shown
in
figure
11
-5 .
The Phase
Detector
Module
develops
a
DC
voltage
proportional
to
the
phase
difference
between
the
reference
and
selected
tower
signals
. The
phase
comparison
is
made
by
a
dual
differential
"coincidence"
amplifier.
This
dual
configuration
cance
l s
the
effects
of
any
asymmetry which
might
be
present
in
the
inputs
and
provides
a
very
precise
phase
indication.
Transistors
Q?
through
QlO
function
as
constant
current
sources.
These
cur
r
ent
sources
establish
the
precise
DC
reference
levels
which
are
necessary
for
accurate
phase
detection.
Inputs
A and
Bare
from
the
re
f
erence
channel
limiter
and
are
always
180
degr
e
es
out
of
phase.
Inputs
C and
Dare
from
the
selected
channel
and
are
also
l80
degrees
out
of
phase.
Transistor
Ql,
2,
3
and
8 form one
phase
detector
circuit.
The
limited
reference
tower
input
is
applied
at
the
base
of
Ql;
the
limited
selected
tower
input
at
the
base
of
Q3.
When
either
input
signal
is
positive,
the
associated
transistor
is
turned
on.
This
places
a
positive
potential
at
the
emitter
of
Q2.
Since
the
Q2
base
is
at
ground
potential
,
it
is
cut
off
under
this
condition.
When
both
inputs
go
negative,
Q2
turns
on.
Thus
the
level
at
the
collector
of
Q2
alternately
switches
in
the
positive
and
negative
directions.
The
width
of
the
negative
going
pu
l
se
is
determined
by
the
time
during
which
both
inputs
are
negative.
This,
in
turn,
is
determined
by
the
phase
angle
between
them.
For
a
zero
phase
angle,
the
signal
at
the
Q2
collector
is
a
symmetrical
square
wave,
and
the
voltage
at
C5
has
its
ma:ximum
negative
value.
The
difference
between
the
voltage
drops
across
resistors
RJO
and
RJ2
is
th
en
zero.
When
the
phase
angle
changes
from O
degrees,
the
positive
going
pulse
at
the
collector
of
Q2
becomes
wider
and
the
voltage
at
C5
becomes more
positive
.
At a
phase
angle
of
180
degr
e
es
there
is
no
current
in
Q2
or
R30, and
this
voltage
reaches
its
maximum
positive
value.
The
voltage
at
C5
is
applied
through
the
180
degrees
push
button
switch
to
the
integrated
ci
rcuit
operational
amplifier
.
This
is
a
high
stability
low
gain
device
which
drives
the
front
panel
PHASE
ANGLE
meter.
Two
other
outputs
are
al
so
provided:
one
for
the
PMA
-
19,
Precision
Monitor
Adapter and
one
for
an
external
application
such
as
an
automatic
logging
device.
These
outputs
may
or
may
not
be
used,
depending
on
the
system.
The
other
half
of
the
phase
detector,
Q)..,
5, 6
and
9 i s
performing
the
same
phase
comparison
but
on
the
inverse
phases.
Since
the
actual
net
charge
on
C5
is
the
result
of
both
comparisons,
any
non-symmetry
in
the
input
is
11
averaged
out"
by
this
circuit
configuration.
Two
adjustments
are
associated
with
the
Phase
Detector
Module:
the
0
degrees
adjustment
and
the
180
degrees
adjustment.
By
selecting
the
in
www.SteamPoweredRadio.Com
use
reference
tower,
there
will
be
a O
degrees
difference
between t
he
two
input
s
to
the
Phase
Detector.
Under
this
condition,
the
ZERO
PHASE
adjustment
is
set
for
a O
degrees
reading
on
the
PHASE
ANGLE
meter.
(The
ZERO
PHASE
potentiometer
is
located
on
the
calibration
sub-panel
behind
the
hinged
front
panel
name
plate.)
With a 180
degrees
phase
difference,
Q2
and
Q5
are
always
cut
off
and
the
charge
on
C5
reaches
the
value
established
by
zener
diode
CR2.
This
condition
is
simulated
by
pressing
the
180
degrees
adjust
switch
which
connects
CR2
directly
to
the
operational
amplifier.
With
the
switch
pressed,
the
180
degrees
potenti-
ometer
is
set
for
a 180
degrees
reading
on
the
PHASE
ANGLE
meter.
This
potenti-
meter
"fine
adjusts"
the
level
at
CR2
by
controlling
the
constant
current
supplied
by
QlO.
Simultaneously,
the
constant
current
supplied
by
Q8
and
Q9
is
also
adjusted.
This
maintains
the
same
current
ratio
through
R30
and
R32
and
minimizes
interaction
between
the
O
degrees
and 180
degrees
adjustments.
However,
there
is
a
slight
amount
of
interaction
between
the
two
adjust-
ments.
The O
degrees
adjustment
should
be
set
first,
then
the
180
degrees
adjustment.
This
procedure
should
be
repeated
until
both
the
adjustments
are
correct.
2.1,5
Current
Meter
Module
The
Current
Meter
Module
schematic
diagram
is
shown
in
figure
11-6.
The
Current
Meter
Module
includes
an
integrated
circuit
operational
amplifier.
This
circuit
provides
isolation
and
gain
between
the
loop
current
detector
and
the
indicating
devices
including
the
LOOP
CURRENT
meter,
the
PMA-19J
and any
external
devices.
This
degree
of
isolation
and
gain
results
in
excel-
lent
stability
and
linearity
over
a wide dynamic
range.
The
gain
of
the
operational
amplifier
is
a
function
of
the
ratio
between
the
feedback
resistor
Rll
and
the
composite
input
resistance
which
includes
R8
and
the
DAY,
CRITical
HOURS
or
NIGHT
potentiometer
selected
by
the
MODE
relays
.
Adjusting
the
LOOP
REFERENCE
potentiometer
changes
the
gain
of
the
amplifier.
Initially
the
LOOP
REFER.ENCE
control
for
each
mode
is
set
to
provide
a
convenient
reference
level,
usually
100%,
with
the
reference
tower
selected.
If
the
reference
tower
is
not
the
highest
current
level
in
the
array,
the
potentiometer
should
be
adjusted
for
some
lower
level
which
will
allow
convenient
reading.
Potentiometer
R7
is
a
factory
adjustment
used
to
compensate
ror
the
forward
drop
which
occurs
across
the
current
detector
diode.
It
is
set
to
..
/J
'/tet-
ll..0
provide
a
slight
up-scale
reading
on
the
meter
with
no
current
input.
(_
4,c:;
w//J.Jttvf~ J
M
'1
tY
Diodes CRl and
CR2
are
limiters
which
prevent
current
surges
from
over-
loading
the
circuit.
Integrated
circuit
A2
is
a
diode
rectifier
which
is
part
of
the
24
volt
DC
supply
for
operation
of
the
relays
and
push
button
lamps.
2 .
1.6
Power
RBgulator
Module
The Power
Regulator
Module
schematic
diagram
is
shown
in
figure
11-7,
2-5
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The Power
Regulator
Module
develops
the
regulated
plus
and minus
12.5
VDC
used
throughout
the
AM-19
,
When
the
unit
is
used
as
part
of
a
PM-19
system,
this
supply
also
furnishes
operating
voltage
to
the
PMA-19.
The
regulators
for
the
+l2.5
and
-l2.5
volt
supplies
are
identical.
The
21
volt
AC
supply
is
rectified
by
bridge
rectifier
CRl
and
filtered
by a
chassis
mounted 500
uf
capacitor
producing
about
26
volts
. Load
current
flows
through
QJ
and
the
chassis
mounted
2N3054
(Ql).
These two
transistors
are
connected
in
a
Darlington
configuration.
Changes
in
output
yoltage,
caused by
either
a change
in
line
voltage
or
load,
are
sensed
by
Q5
through
divider
R8, R7, and
Rll.
Zener
diode
CR9
maintains
the
emitter
of
Q5
at
a
constant
-6.2
volts.
The
output
variations
are
amplified
by
Q5
and
applied
to
the
base
of
Q3,
changing
the
series
resistance
in
the
direction
that
opposes
the
original
output
voltage
change.
Rll
is
adjusted
to
set
the
output
voltage
at
exactly
12.5
volts.
Transistor
Ql
is
a
high
impedance
collector
load
for
Q5,
In
conjunction
with
RJ, R5, and
CR3,
it
provides
short
circuit
protection
for
the
regulator.
If
the
load
current
increases
to
about
300
MA,
the
voltage
drop
across
R5
causes
CR?
to
condust.
Q4
then
becomes
nearly
cut
off,
limiting
the
current
into
the
collector
of
Q3
and
increasing
the
resistance
of
the
series
transistor
.
An
equilibrium
point
is
reached
when
the
load
current
is
limited
to
JOO
MA
even
if
the
load
resistance
is
reduced
to
a
short
circuit.
Temperature compensation
is
provided
in
several
places.
CR.4
compensates
for
the
temperature
change
of
the
base-emitter
diode
of
Q4.
CR8
is
a
temperature
compensated
zener
diode
having.a
temperature
coefficient
of
.005%/degree
C.
CRll and
CR12
compensate
for
the
temperature
range
of
the
base-emitter
diode
of
Q3.
2-6
www.SteamPoweredRadio.Com
SECTION
3
INSTAILATION
AM
-
19
3.1
Inspection
After
carefully
unpacking
the
instrument,
check
that
the
follo'Wing
items
have been
included
with
the
AM-19:
a.
One
per
unit
-
Instruction
Manual
b.
One
per
unit
-Power
cord,
3
conductor
'With
3-prong
U-grounding
plug.
c.
One
per
unit
(supplied
with
remote
metering
panel)
-Remote
control
connector,
33
contact
plug,
Cinch-
Jones
P- 333-
CCT.
Inspect
the
packing
cartons,
particularly
the
inner
box,
for
any
indica-
tion
of
damage
to
the
equipment
in
shipment.
Thoroughly
inspect
the
Antenna
Monitor.
Check
all
sides
of
the
unit
for
signs
of
damage, check
the
meters,
operate
all
controls
checking
for
looseness
or
binding.
If
there
are
any
signs
of
rough
handling,
remove
the
top
and bottom
covers,
look
for
broken 'Wires and
check
that
all
plug
-
in
modules
are
properly
seated.
NOTE:
The
AM
-
19
includes
two
identical
limiter
moduJ.es. However,
these
modules
cannot
be
interchanged
'Without
upsetting
certain
factory
adjustments.
If
it
is
necessary
to
remove
any
modules,
be
sure
each
board
is
plugged
back
into
the
original
socket.
On
some
mod-els
the
reed
relays
located
on
the
input
modules
are
plugged
into
pin
sockets.
Also check
that
these
relays
are
properly
seated.
The
shipping
container
has
been
specifically
designed
to
protect
this
equipment from damage
during
normal
transport.
Any
physical
damage
to.the
monitor
is
an
indication
of
gross
mishandling
and
the
carrier
should
be
notified
innnediately.
It
is
strongly
suggested
that
the
inner
and
outer
shipping
cartons
and
all
filler
and
pads
be
retained
at
least
until
the
monitor
has
been checked
out
and
is
operating
properly
in
the
system.
In
the
event
the
unit
must
be
returned
to
the
factory,
SHIPMENT
:m
AN
IMPROPER
CONTAINER
MAY
VOID
THE
WARRANTEE.
3.2
Monitor
Configuration
Before
mounting
the
AM
-
19,
determine
that
the
monitor
configuration
complies
with
all
requirements
of
the
installation.
The number
of
TOWER
push
buttons
and
rear
panel
coaxial
receptacles
should
correspond
to
the
number
of
towers
in
the
array.
For
a
single
pattern
(DA
-
l,
DA
-
Dor
DA-N)
array
the
monitor
will
include
a
push
button
POWER
s'Witch, a
RMT
(remote)
push
button,
a
RLS
(release)
push
button
and one
LOOP
REFERENCE
ten-turn
counting
dial.
Calibration
adjustments
are
located
on
the
calibration
sub-panel
behind
the
hinged
door
on
the
lower
left
area
of
the
front
panel.
For
a two
pattern
(DA
-
2)
array
the
monitor
will
include
two
additional
MODE
push
buttons
for
DAY
and
NIGHT,
and
LOOP
REFERENCE
dials
for
both
DAY
and
NIGHT.
For
a
three
pattern
(DA-3)
array
the
monitor
will
include
.3-1
This manual suits for next models
4
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