Broadcast BTS-101A User manual

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Broadcast Equipment
BTS-101A
Stereo
Generator
Ml-561061A
18-8025127

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WARNING
VOLTAGES
THAT
ARE
DANGERO
US
TO
LIFE
ARE
INVOLV
ED
IN
THE
OPERATION
OF
THIS ELEC-
TRONIC
EQUIPMENT.
OPERATIN
G PERSONNEL
MUST
AT
ALL
TIM
ES
OBSERVE
ALL
SAFETY
REGULATIONS. DO
NOT
C
HANGE
TUB
ES
OR
MAKE
ADJUSTMENTS
INSIDE
THE
EQUIPMENT
WITH VOLTAG
ES
APPLIED
. DANGEROUS CONDI-
TIONS
MAY
EXIST
IN
CIRCUITS
WITH
POWER
CONTROLS
IN
THE
OFF
PO
SITION
DUE
TO
CHARGES
RETAINED
BY
CAPACITORS, ETC.
ALWAYS
DISCHARGE
AND
GROUND
CIRCUITS
PRIOR TO TOUCHING THEM TO
AVOID
PERSONAL
INJURY
OR
LOSS
OF
LIFE.
EMERGENCY
FIRST
AID
INSTRUCTIONS
P
ersonnel
en
gaged
in
the
installation,
operation,
01
maintendnce
ot
this
equipment
or
simila
r
equipment
are
urged
to
become
familiar
with
the
following
rules
both
1n
theory
and
p,ac11ce. It is
the
duty
of
all
operating
personnel
to
be
prepared
to
give
adequate
Em
er
g
enc
y
Fir
st
Aid
and
th
ereby
p,
eve
rH
avoidable
l
oss
ot
life.
1.
Find
ou
t 1f
the person
,s
breathing.
You
must
find
out
11
the
person
has
st
opped
breathing.
If
you
think
he
is
not
breathing,
place
him
fl
at
on
his
back.
P
ut
your
ear
close
to
his
mouth
and
look
at
his
ches
t. If
he
is
breathing,
you
can
feel
the
air
on
y
ou
r
chee
k.
You
can
see
his c
hest
move
up
and
down.
ff
you
do
not
f
ee
l
the
air
or
see
th
e
chest
move,
he
is
not
breathing.
RES
CUE
BREATHING
2.
If
he
1s
11u1,
0 1
M1
the
c1i1wuy
by
rilting
his
ht!od
b,,ckwa
,
d.
Lift
up
h,~
nec.:k
wnll
one
hd11d
a11d
push
duwn
0 11
111~
to,chedd
with
1
he
1
Hh
e1.
Th,s
oµe
11
s
th
e
ai,way.
Sometimes
doing
1h1s
will
let
the
person
breathe
dga111
by
himself.
If
1t
du,?)
not,
h
eg111
rf)
scue
b1
e<1
t
h11
'H·
BURNS
3.
If
he
is
stil
l
1101
breathi11g,
begin
rescue
breath
ing
:
Keep
his
head
tilted
backward.
Pinch
h,s
nose
shut.
Put
you
,
mouth
tight
ly
over
his
mou
t
h.
Blow
into
his
mouth
once
every
five
seconds.
Do
Not
Stop
R
escue
Breath
ing
Until
Help
Comes.
LOOSEN
CLOTHING
-KEEP WARM
Do
this
when
th
e
victim
1s
breath-
1119
by
himse
lf
or
help
is
avail
able.
Keep
him
quiet
as
possible
and
I,
om
becoming
chilled.
Otherwise,
t1ea1
him
lo,
shock.
SKIN
REDDENED:
Apply
ice
cold
wa
tc,
to
bumetl
d1ea
to
prevent
burn
from
go
ing
deeper
11110
skin
tissue.
Cover
area
with
clean
sheet
o,
cloth
to
keep
awdy
a11.
Consult
a
physician.
Jeepe1
111!0
~k111
tissue.
Cove,
area
with
c l
ean
shee
t
or
cloth
10
kt:ep
away
air.
Treat
victim
for
shoc
k
and
take
to
ho
spital.
SKIN
BLISTERED OR
FLESH
CHARRED.
Apply
,ce
cold
wa
tet
to
burned
area
to
prevent
h111
n
f1
om
90111q
EXTENS
IVE
BURN
-S
KIN
BRO
KEN
:
Cover
area
with
cl~.111
sheet
or
cloth
to
keep
<1way
a,r.
T
rea
t
victim
for
shock
and
tdke
to
hosµital.

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Broadcast Equipment
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• • • •
Instructions
BTS-101A
Stereo
Generator
Ml-561061A
Commercial
Communications
Systems
Div
ision/
Front
and
Cooper
Streets
/
Camden,
New
Jersey,
U.S.
A.
,
08102
PAINTED
IN
U.S.A.
DL
779
M
IB-8025127

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II
SAFETY PRECAUTIONS
This
equipment
1s
designed to fu
ll
y
sa
feguard a
ll
pe
rsonnel fr
om
ope
rati
ng
hazards. Labels
on
the
equipment and caution notices in
the
instruction
book
clearly
point
out
these potential hazards.
Any
module
or
Printed Wiring Board
may
have hazardous voltages exposed, so
caution
must
be
exercised.
Follow
the
recommended procedures provided in
the
Instruction Book for
care
and maintenance
of
the
equipment.
Always replace
the
protective covers after servicing
the
equipment.
WARRANTY
ITEMS
Particular t
arts
and/or
equipment
covered
by
warranty
are
specifically
stated
as such
1n
the
war
r
anty
or
co
n
tract
given
to
the
cust
om
er
at
the
time
of
sale.
The
warranty
or
contract
also stipulates
the
conditions under which
the
war
-
rdnty
may
be
exercised.
To
obrn1n a new replacement for such warranty items, c
ontac
t
your
local RCA
sales
office
and please supply Product Identification (including
the
Original
Invoice Number,
Ml
Number,
Type
Number, Model Number, and Serial
Number) and Replacement Part I
de
ntification
(i
ncluding
Stoc
k Number
and
Descr
1p11on).
Requests for
warranty
replacements may
be
undu
ly
de
layed if al l
this
nformat,on
1s
not
supplied.
EQUIPMENT LOST OR DAMAGED
IN
TRANSIT
When del1ver1ng
the
equipment
to
you,
the
truck
driver
or
carrier's agent will
p,esent a receipt
for
your
signature. Do not sign ,t until
you
have (a) inspected
the
contd1ners fo, visible signs
of
damage and (bl counted
the
containers and
compared
with
the
amount
shown
on
the
shipping papers.
If
a shortage
or
1f
evidence of damage
1s
noted,
inmt
that
notation
to
that eff
ect
be
made
on
the
sh1pp1ng
papers
before
you sign them.
Furthe1.
after
rcce1v1ng
the
equipment,
unpack n and inspect thoroughly for
concealed damage. If concealed damage
1s
discovered. immediately notify the
carrier, confirming
the
not1f1cat1on in writing, and secure
an
inspection report.
This ,tern should
be
unpacked and inspected for damage WITHIN
15
DAYS
after receipt. Report all shortages and damages
to
RCA, Communication
Systems D
1v1sion
Camden, New Jersey
08102.
RCA will file all claims for loss and damage
on
this equipment so long
as
the
inspection repo1t
1s
obtdined.
D1spos1t1on
of
the
damaged it
em
will
be
furnished
by
RCA.
FIE
LD
ENGINEERING SERVICE
RCA Field
Eng1n
ee11ng
Se1v1ce
1s
av.iilaule
at
current
rates. Requests for field
engineering
serv1CI'
may be add,essed
to
your
RCA Broadcast Field Representa•
live
or
the
RCA Service Company, Incorporated Broadcast Service Div
is
ion
Camden, New Jr,rsey
08102.
Telephone
(609) 338
-3
434.
TECH
ALERT
Emergency
24
hour tF>lephone
consultation
service for technical
problems
1s
available. Call TECH
ALERT
at
[phone].
Telex messages will be for•
warded
to
the
addressee upon receipt. Western Union
te
lex
numbe
r
is
83-4450.

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TECHNICAL SUMMARY
LIST OF EQUIPMENT
RECOMMENDED TEST EQUIPMENT
GENERAL DESCRIPTION
INSTALLATION
Ge ner al
TABLE OF CONTENTS
Mounting the Interconnect Cab le
Connections to the Main Cable Connector
Stereo Generator in other Applications
Final Mounting ...
Interface/Radiate Panel
Exciter Unit
Stereo Generator
ROUTINE OPERATION .. .
DETAILED CIRCUIT DESCRIPTION
FIELD MODIFICATIONS . .. ..
Power - up to Monau r al
Mono So urce Selection
Rewiring Power Transformer for 240 V ac Input
ALIGNMENT PROCEDURE . . .
Test Equipment
Powe r Supply Check ..
Audio Stage Alignment
Audio Filter Alignment
Sepa
ration Adjustment
Pilot Adjustment ..
Remote Functions ...
Final Considerations.
PARTS ORDERING INFORMATION
Replacement Parts
Emergency Part Service
REPLACEMENT PARTS . . . .
SUGGESTED STATION SPARES
LIST OF ILLUSTRATIONS
Title
Figure
1A
B Front Panel
Controls and Indicators
Rear View
2
3
Ste r eo Generator Block Diagram
Oscilloscope
Wa vef orms
III
Page
V
VI
VI
2
2
2
5
6
6
7
7
7
7
8
11
11
11
11
11
11
12
12
14
14
15
17
17
18
18
18
19
Page
1
1
3
16

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IV
Figure
4
5
6
7
8
9
10
11
12
13
14
15
LIST OF ILLUSTRATIONS (Continued)
Title
BTS - 101A Top View
PW Board Switches and Adjustments
Dual
Input Pad Components Location
BTS - 10 1A S tereo Generator Schematic
!\udio
Lowpass Filter Schema ti c
Aud io Lowpass Filter Components Location
53 kHz Filter Schematic
53 kHz Filter Components Location
BTS -1 01A Stereo Generator Components Location
Intercon nectin g Cable Schema t ic
Precision Differential Test Ge nerat or Schematic
De -emphasis Network Schematic
Page
25
26
26
27
29
29
30
30
31
33
35
37

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V
TECHNICAL
SUMMARY
PERFORMANCE
Audio Input Impedance . .
Audio
Input
Level
..
. .
Audio Frequency Response
Harmonic
Distortion
...
Intermodulation
Distortion
Signal
to
Noise
Ra
ti
o
...
Pilot
Carrier
Stability
..
Separation
.......
.
Subcarrier
Suppression
(referred
to
Crosstalk
Without Audio
Low
Pass
Filter
..
With Audio
Low
Pass
Filter
..
.
Pre-Emphasis Network
Time
Constant
Output Level
.....
Output Impendance (See Note 1)
ELECTRICAL
Resistive
600 ohms, Balanced
+10
dBm+ 2
dB
at
400
Hz
+1
dB,
30-
Hz
to
15,000
Hz
- 0.
5%
or
less
0.
3%
or
less
..
70
dB
19
kHz
+1
Hz
40 dB
100%
modulation)
50
dB
45
dB
40
dB
0,
25,
50
or
75
usec
,
switchable
3.5
volts
peak-to-peak
. . . . . . . . 1
80
ohms
Power
Line Requirements . . . .
120
or
240
volts,
single
phase, 50/60
Hz
Combined
Line Voltage
Variation
and
Regulation . . . .
+10%
Power
Consumption. . . . . . . .
...
......
.....
10
watts
max.
MECHANICAL
Dimensions,
inches
(cm)
(overall):
Width
Height
Depth
Weight, pounds (kg) .
Altitude,
feet
(meters)
Ambient
Tempe
r
atu
re
. .
.
19
(48.
3)
1.
75
(4.4)
9
(22.9)
7.
125
(3.23)
7500 (2286)
max.
-
200C
to
+7
00C
(-
40F
to
+1
400f)
NOTE
1.
The
BTS
-
101A
will
meet
all
listed
performance
specifications
with
up
to
10
feet
of
RG-58/U
cable
feeding
into
a
load
impedance
of
5000
ohms
or
greater;
and
will
me
et
all
FCC
rule
s
in
effect
as
of
date
of
manufacture
with
up
to
50
feet
of
RG
-58/U
cable
.

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VI
LIST OF EQUIPMENT
BTS-101A Stereo Generator, less two Audio Lowpass Filters
Plug-in 15 kllz Lowpass Filters (two) .... . .... .
MI - 561061A
MI -561064
Complete
set of connector plugs for the BTS - 101A
Stereo Generator ( requi . red only when Interface
Panel MI-561071 and/or Interconnecting Cable
MI -561067 are not used) (optional)
Set of chassis slides for servici.ng (optional)
Drilling Template for mounting units (optional)
RECOMMEHDED TEST EQUIPMENT
Precision AC Voltmeter
Audio
Oscillator
Sweep Generator
Precision Differential
Amplifier
DC Voltmeter
De -emphasis Network
Oscilloscope
H.P . 400FL or equivalent
H.P . 200CD or equivalent
Wavetec #180 or equivalent
See figure 14.
Simpson 260
or equivalent
See figure 15.
Tektronix Type 531 with Type H
plug - in or equivalent. Scope
requirements are detailed in
the Separation Adjustment
procedure.
MI -561069
MI-561073
3742738
Stereo FM Monitor
BW - 85A (BW -185) fitted with external
input attenuator (5K pot connected
through a ma x imum of two (2) fee t
of RG -58/U to the monitor 's
baseband
input).
I
I

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STEREO MODE MONO OUTPUT
LEVEL
RI0:3
SEPARATION SEPARATION
CRIOI SIOI CRlO2
LEFT RIGHT
lij00(13lX}
........... YOa ,,. •. ,o,
FIOI
XFIOI
A
B
0111tll'11• o:u•••',•
t,h •••..:.t
INPUTS
JIOI
•
RIOI Rl02
COMPOSITE
STEREOPHONIC
OUTPUT
JI02
IK218
figure 1. BTS - 101A External Views
GENERAL DESCRIPTION
The BTS - 101A is a completely self - contained stereo generator needing no parent
equipment to generate the
specifically to operate in
DTS - 101A may be used in
high - quality stereo signal .
adjusted without the need of
composite sterephonic signal . Al though designed
conjunction with the RCA BTE - 11 5 FM E xciter, the
any application requ1r1ng the gene ration of a
Since it is self-contained, it may be tested and
an
exciter.
A pair of program audio signals, preferably processed by the RCA BA -150 Digital
Overshoot Compensation (DOC) Processor, are applied to the input of the unit.
(See block diagram, figure 2) . These signals are routed through the rf filter
to the internal printed wiring board. Each channel signal is then pre -
emphasized and
applied to a 15 kHz audio lowpass filter . The pre -emphasis is
adjustable and both the pre -emphasis and the audio lowpass filter are switch
defeatable. The two audio channels, thus processed, are applied to the analog
inputs of an electronic switch operating at 38 kHz . The 38 kHz switching sig -
nal and the 19 kHz pilot tones are both derived from a stable 3.04 MHz crystal
oscillator. The output of the electronic switch is applied to a phase- linear
lowpass filter to remove unwanted switching - signal components. The filter
output is amplified to a level of 3.5 volts peak- to -peak for application to the
following equipment, normally the BTE - 115 Exciter. In addition to the normal
composite
signal output, the BTS - 101A delivers a pair of audio signal samples,
representative of the individual audio channel modulationg signals, for appli -
cation to the metering system of an affiliated BTE -115 FM Exciter. Remote mode

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2
switching connections are located at the rear connector. A momentary closure
to ground is needed to switch modes; an internal latch keeps the unit in the
selected mode .
INSTALLATION
GENERAL
This procedure covers installation of the BTS - 101A Stereo Generator either in
other applications or when used with the BTE -1 15 Exciter in the following RCA
transmitters.
BTF - 3ES1
BTF - 5ES2
BTF - 5ES1
BTF - 10ES1
8TF-20ES1
referred to in text as BTF 3/5
referred to in text as BTF 5/10/20
This procedure can generally be applied to other FM exciters and transmitters
as well. Drilling and tapping of the required mounting holes in the cabinet
should already have been accomplished in these RCA transmitters (see BTE -1 15
Exciter Unit Instruction Book IB-8025256- 1), and the transmitter should be
prepared for exciter installation using the instructions.
MOUNTING THE INTERCONNECT CABLE
An interconnecting cable assembly, MI -561067- 4, - 5, or - 6 may be supplied with
the exciter system, and may already be installed in the transmitter . This
cable interconnects the stereo generator to the BTE -115 exciter unit, and also
provides for inputs to the system .
In the BTF - 5/10/20 transmitter (if not already installed) , mount the intercon -
nect cable along the inside edge of the front left hand mounting r ail in the
transmitter, using flat head screws and cable ties provided with the cable as
required. The cable should be positioned so the end with the 24 pin connector
extends toward the bottom of the transmitter, and such that the two, th r ee , or
four legs of the cable will breakout in the area where the associated units
will be mounted . Connect the cable to the existing transmitter wiring, and
coil any excess length in the bottom of the transmitter.
For the BTF - 3/5 transmitter, mount the cable as shown in figure 7 of either
the BTF - 3ES1 (IB-8027593-1) or the BTF -5ES2 (IB-8027984- 1) Instruction Book.
When the optional chassis slides MI -561073 are used, the same holes are used
for mounting the chassis slides and the cable ties. Refer to instructions
provided with the chassis slides for installation details.

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FT
-
LE
PRO
IN P
GRAM
UT
GHT _
RI
PRO
-
GRAM
I NP UT
IN PUT
-
-
TERMINATION
GAi N
IN PUT
-
TERMINATION
POWER
SUPPLY .
PRE EMPHASIS
(ACT IVE)
'
·'JI
)
◄
A
> 0 0
')
PRE-EMPHASIS
PRE EMPHASIS
-
(ACTIVE)
◄
tvECTOR
)
CROSSTALK
ADJUSTMENT
...
-
-
LP F
r-------
)
~
0
'
IN OUT
\
~
,.
1----'
L P F
-
.
I
0
I
IN OUT
3,04 MHz
--
CLOCK
7
t
PILOT
FREQUENCY
METERINh
SAMPLE S Ill
BTE-11~
L
ELECTRON !<
SWITCH
I
I
R
38kH z
DIVIDERS
AMPLIFIER
STEREO
GAIN
DIVIDER
l9kHz
U!ll,11 3K041
19kHz
SINUSOIDALIZI G
t-- - ~
LOW PASS
OUT PUT
PILOT
PHASE TANK
l.,L T
I PH S IN G
OUTPUT
AMPLIFIER
STER 0/ MONO
MOOE LATCH
MODE
REMOTE
3/4
COMPOSITE
OUT PUT TO
EXCITER.
FI I' w 1• ?. St e reo Genera tor Block D iagram

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CONNECTIONS TO THE MAIN CABLE CONNECTOR
The 24 pin plug on the interconnect cable provides for audio input to and
remote
control of the exciter system. Connect as follows:
1. BTF-3/5 Transmitter - Install the mating connector supplied with the
interconnect cable as item 2. Bring audio input and remote control
lines directly to this connector as follows:
Circuit
Pin Numbers
Left
Audio Input
1 &2
Shield
3
Right
Aud io Input
4 &5
Shield
6
Remote Stereo On
16
Remote Mono On
17
Remote Common
18
If SCA Unit is to be used, do not re-assemble connector cover, as additional
wires will be added.
Operational Note: Momentarily shorting pin 16 to pin 18 causes
stereo ope ration . Momenarily shorting pin 17 to 18 causes mon -
aural operation, using the left input signal as the mono source.
2. BTF-5/10/20 Transmitter - If the transmitter is not equipped with a
24
pin plug to mate with the interconnect cable, use the connector
supplied with the interconnect cable as i tern 2. Remove existing
connectors from cables Nos. 201 thru 204 and connect these cables to
the 24 pin plug as follows:
Cable ti To Pin ti
Shield
Circuit
Red
Black
201
1 2 No Connection Left Audio In
202 4 5 No Connection Right Audio In
203 10 11 No Connection SCA #1 Audio In
204
13
14
No Connection SCA 112 Audio In

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6
Remove
wires
number
514, 516, and 517
from
the
cable
harness
that
was
removed from
the
transmitter
during
the
installation
of
the
BTE-115
exciter.
Connect
these
wires
from
1TB6
to
the
24
pin
connector
as
follows:
Wire
II
From
To
Pin
II
Circuit
514
1TB6-15
17
Remote
Mono
On
516
1TB6-17
16
Remote
Stereo
On
517
1TB6-18
18
Remote
Cormion
If
SCA
Unit
is
to
be used,
do
not
re-assemble connector
cover,
as
additional
wires
will
be added
to
this
connector.
Operational Note: Momentarily
shorting
1TB6-17
to
1TB6-18
causes normal
stereo
operation.
Momentarily
shorting
1TB6-15
to
1TB6-18
causes
monaural
operation,
using
the
left
input
signal
as
the
mono
source.
STEREO
GENERATOR
IN
OTHER
APPLICATIONS
For
installations
where
the
stereo
generator
is
not
mounted
adjacent
to
the
BTE-115
exciter
as
well
as
operation
remote from
the
transmitter,
the
inter-
connect
cable
will
not
be
utilized.
In
this
case,
a complete
set
of
connectors
for
the
stereo
generator
may
be
ordered
as
MI-561069
and a complete
set
of
connectors
for
the
BTE-115
may
be ordered
as
MI-561068. Item 1
of
connector
kit
MI-561069, which mates with J101, must be
utilized.
Connect audio
input
and
mode
control
lines
to
this
connector
as
follows:
Circuit
Pin
Number
Left
Audio
Input High 6
Left
Audio
Input
Low
3
Shield
2
Right
Audio
Input
High 4
Right
Audio
Input
Low
1
Shield
5
Remote
Stereo
On
10
Remote
Mono
On
12
Common
11
Operational Note: Momentarily
shorting
pin
10
to
pin
11
causes
stereo
opera-
tion.
Momentarily
shorting
pin
12
to
pin
11
causes monaural
operation.
Swi-
tching
may
be accomplished
by
a
switch,
pushbutton,
relay
or
NPN
transistor.
FINAL
t-OUNTING
For systems
utilizing
an
SCA
generator,
omit
the
remainder
of
this
installation
procedure and go
to
the
installation
instructions
for
that
unit.
If
no
SCA
is
to
be used, mount
the
Exciter
System Components
as
follows:

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r--..
7
INTERFACE/RADIATE PANEL
Mount panel in place and connect the 4 pin plug and ac twist-lock connector to
the panel. Dress associated cables t o not interfere with removal of the
exciter or stereo generator for servicing.
EXCITER UNIT
Connect the umbilical cord extending from the interface panel to the 6 pin
control connector at the rear of the exciter. Connect the 10 pin plug on the
interconnect cabl e to the mating input connector on the exciter. Connect the
associated rf connector from the interconnect cable to the composite input on
the exciter. (If there a re additional rf connectors on this cable, they will
be labeled "SCA" an should connect to the SCA INPUT on the exciter). Connect
the rf output and ac power cables to the exciter, and mount the exciter in
place.
STEREO GENERATOR
Connect the 12 pin connector on the interconnect cabl e to the INPUT connector
J 101 of the stereo generator , and the associated r f connector to the OUTPUT
jack J102. Plug accord into the interface panel. Mount stereo generator.
Fill unused space(s) wi th blank panels.
ROUTINE OPERATION
Frequent readjustment of the BTS-101A circuitry is not normally necessary.
Occasional manual or remote mode switching will be the most common operation.
The transmission mode may be switched from stereophonic to monaural (with a
preselected audio channel for the source), and back. Switching can be
accomplished by a momentary
(or continuous) connection to ground, and that
connection can be accomplished by a switch, pushbutton, relay or NPN
transistor . The selected mode is indicated by the light-emitting diode stereo
or mono indicator lamp. Refer to the schematic diagram, figure 7.
The stereo pilot shoul d be held at a level of 9%. The most convenient method
of trimming this level is the front-panel OUTPUT LEVEL control . This is a
vernier adjustment, with a few dB of range . Should the desired setting of this
control be at an extreme of its range, resetting the internal PILOT LEVEL
control R46 may be called for, or resetting the audio limiter outputs may be in
order. See Alignment Procedure. The normal output l evel from the BTS-101A is
3.5 volts peak- to -peak for 100% modulation. This should occur with a 10 d&n
input level.
The SEPARATION control settings should be checked during routine proof of
performance checks. Separation tests will requ i re that prograrrnning material be
removed from
the channel under test.

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8
DETAILED
CIRCUIT
DESCRIPTION
Left
and
right
audio
signals
are
applied
to
the
INPUTS
connector
J101 on
the
rear
of
the
BTS-101A.
Refer
to
the
schematic
diagram,
figure
7.
The
left
channel
is
connected
to
pins
3 and
6,
while
the
right
channel
is
connected
to
pins
1 and
4.
Pins
2,
5,
8,
and
11
are
available
to
ground
the
shields
of
these
lines.
The
audio
signals
are
routed
to
the
printed
wiring
board
through
rf
filters
composed
of
L101, L102, L103, and L104
operating
in
conjunction
with
capacitors
C101, C102, C103, and C104.
Following
the
rf
filtering,
the
signals
are
applied
to
the
input
pads
and
transformers
T102 and T103.
The
left
channel
input
transformer
is
terminated
by
R5,
in
parallel
with
R6,
R7,
and
R8. The
range
of
the
LEFT
GAIN
control
R7
is
restricted
by
R6
and
RS.
The
output
from
R7
is
applied
to
R9,
which,
with
C1,
forms
an on-
board
rf
filter.
The
output
of
this
filter
is
then
amplified
by
U1.
Capacitor
C4
is
placed
in
the
negative
feedback
loop
of
U1
to
cause
a
very
slight
but
predictable
phase
lag
at
15
kHz. The
output
of
amplifier
Ul
is
fed
into
a
phase
correction
network
comprised
of
R12, R13, and C6,
to
allow
low
audio
frequency
square
wave
transmission.
Capacitor
C5
is
added
to
this
network
to
compensate
for
a
slight
high-frequency
loss
at
15
kHz
in
the
audio
lowpass
filters
. The
signal
is
then
fed
to
amplifier
U2
which
functions
as
an
active
pre-emphasis
network.
The
pre-emphasis
time-constant
is
determined
essentially
by
the
sum
of
R15
and
R16
operating
in
conjunction
with
capacitor(s)
C12
and C13. A
flat
frequency
response
is
obtained
by
switching
out
both
C12
and C13. A
50µs
time-constant
is
obtained
by
switching
in
C13
only;
75µs
is
obtined
by
also
switching
in
C12.
In
either
case,
LEFT
PRE-EMPIIASIS
control
R
15
is
adjusted
for
the
correct
frequency
response.
The
output
of
U2
is
applied
to
the
15
kHz
audio
lowpass
filter
FL
1
via
series
terminating
resistor
R18. The
filter
output,
terminated
by
R20
is
applied
to
buffer
U3
(to
drive
the
electronic
switch
for
stereo
generation)
and
to
U7
(to
drive
the
metering
system
in
the
BTE-115
FM
Exciter).
C14
limits
the
audio
noise
bandwidth
to
60
kHz
when
the
audio
lowpass
filter
is
switched
out.
The
right
audio
channel
functions
in
a manner
similar
to
the
left
except
that
various
adjustments
have
been
added
to
enable
precise
audio
channel
phase
and
amplitude
tracking
to
easily
allow
linear
crosstalk
cancellation.
Specifi-
cally,
150
Hz
control
R28
allows
the
individual
audio
channels
to
be
adjusted
to
an
identical
value
at
low
frequencies.
When
the
pre-emphasis
is
switched
out,
15
kHz
(FLAT)
control
C24
should
be
adjusted
for
audio
channe
l
phase
tracking
at
15
kHz.
When
the
pre-emphases
is
switched
in,
1500
Hz
control
R37
enables
the
right
pre-emphasis
time-constant
to
be
trimmed
to
agree
with
that
obtained
in
the
left
channel.
Phase
agreement
at
15
kHz
is
enabled
by
15
kHz
control
R35.
The
output
of
U4
is
applied
to
the
15
kHz
audio
lowpass
filter
FL2
for
the
right
channel
through
series
terminating
resistor
R40.
Filter
output
is
termi-
nated
by
R42
and -
is
applied
to
buffer
U6
(
to
drive
the
electronic
switch
for
the
stereo
generation
process),
and
to
US
(to
provide
an
audio
sample
for
the
affiliated
BTE
-115
Exciter
metering
system).
C35
limits
the
audio
noise
bandwidth
to
60
kHz
when
the
audio
lowpass
filter
is
switched
out.

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9
The outputs of U3 and U6 are applied to the electronic switch U9 through de
blocking capacitors C18, C19, C39, and C40. D iodes CR5 and CR6 prevent the
blocking capacitors from becoming reverse-biased by power on and power off
transients. The transmission of the left signal from pin 3 to pin 2 of the
electronic switch is controlled by the switching signal applied to pin 1. A 38
kHz square wave from U15 is applied to this pin, resulting in a left channel
signal, switched on and off at a 38 kHz rate, being present at pin 2. Like-
wise, the right channel signal is transmitted from pin 6 to pin 7, controlled
by a 38 kHz square wave applied to pin 8. However, the control signal at pin 8
is 1800 out of phase with the control signal at pin 1. Therefore, pins 2 and 7
can be connected together and the resultant signal at the combined point will
switch from left to right at a 38 kHz rate. The output of the electronic
switch is applied to summing amplifier U10 through resistors R57 and R58.
Capacitor C22 limits the maximum slow rate from the electronic switch to less
than 50 volts per microsecond, thereby insuring that transient intermodulation
distortion products will not be generated in the summing amplifier. Separation-
correction signals from LEFT SEPARATION control R 101 through R59 and RIGHT
SEPARATION control R102 through R44 are also applied to the summing amplifier.
The pilot signal is derived from a 3.04 MHz crystal oscillator formed by Q1 and
associated components. The frequency of this oscilla tor is determined pri-
marily by crystal Y1. The signal may be trimmed to the desired frequency
(corresponding to a pilot-tone frequency of 19.0 kHz) by PILOT FREQUENCY capaci-
tor C54. Transistor Q2 interfaces the oscillator into the logic buffer U12B.
The output of U12B at pin 4 is a pulse at a rate of 3. 04 MHz and is applied to
divider U13 for div i sion down to 304 kHz. The output of U13 at pin 11 is
applied to the input of U14, which divides the signal down to 76 kHz. The out-
put of U14 at pin 9 drives the final divider U 15. The outputs at U15 pins 5
and 6 are the aforementioned out of phase 38 kHz pulses which drive the
electronic switch U9. A 19 kHz signal is also supplied by divider U15 at pin
9. The 19 kHz signal is buffered by U12A and is then applied to buffers 03 and
Q4. The l
ow impedance of this stage provides drive for the pilot filter con-
sisting of L1 and PILOT PHASE control C58. L1 permits phasing or timing of the
pilot tone relative to the 38 kHz switching signal . The outpu t of PILOT LEVEL
control R46, a sinusoid, is applied to the summing amplifier through R45.
GAIN of the summing amplifier U10 i s determined by STEREO GAIN control R61,
whose
range is limited by R60. The output of this stage is applied t o the
phase-linear 53 kHz lowpass filter FL3 through series terminating resistor R63.
The
filter output is terminated primarily by R64. This filter attenuates any
signal component above 53 kHz. This results in a smoothing out of the switched
pulse left and right signal into a continuous wave.
Signal input to the output buffer amplifier U11 is determined by K 1, which
selects either the mono input from pin Mor the stereo signal appearing across
R64. The mono signal source is determined by the connection to pin M of either
the left channel (L) input or the right channel (R) input. The unit is nor-
mally wired to utilize the left channel signal, but conversion in the field to
supply the ri ght channel signal for mono transmission may be easily accom-
plished. Refer to the FIELD MODIFICATIONS section, Mono Source Selection and
to fi g ures 5 and 7. To eliminate the possibility of phase-cancellation pro-
blems in the interconnecting link between the program source and the transmit-
ter site, only one audio channel at a time is accepted for transmission in the
mono mode. For p rop er channel balance, both the L and R cables m ust remain
connected to their respective terminals.

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10
Relay
K1
is
controlled
by
transistor
Q5.
This
transistor
is
part
of
a
latching
circuit
inv
olv
ing
Q5, Q6,
Q7
and
QB.
This
latch
may
be
switched
from one
mode
to
the
other
by
operating
either
the
front
panel
mode
switch
or
by momentary
connection
to
ground
of
the
remote
control
terminals,
J101,
pin
10
or 1
2.
A
transistor
or
open-collector
TTL
gate
may
be used
to
accomplish
rem
ote
control
switching.
Capacitor
C60
simulates
closing
of
S101
to
the
STEREO
position
so
that
th
e
latch
will
set
to
the
STEREO
mode
upon each
application
of
power.
If
it
is
desired
to
power up
to
monaural
operation,
move
C60
to th
e
equivalent
position
near
Q7.
Installing
C60
in
the
alternate
position
is
described
in
the
FIELD
MODIFICATIONS
section,
Power
Up
to
Monaural.
Light-emitting
diodes
CR101
and
CR102
indicate
the
mode
status
on
the
front
panel.
The
power
supply
is
of
conventional
design,
with
a
split-primary
power
transformer,
full
wave
rectification,
and
electron
ic
regulation
of
critical
voltages.

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11
FIELD MODIFICATIONS
POWER-UP TO MONA U RAL
The BTS-101A is normally shipped from the factory wired to return to the
st ereophonic mode of operation at turn-on or following a power failure . Should
it be necessary to return to the monaural mode following a power failure, one
capacitor must be moved. Locate C60 (10 MF 20 volts) on the components layout
drawing, figure 5, and the BTS-101A top view, figure 4, and carefully de-solder
it from the printed wiring board. Reinstall the capacitor in the pair of hol es
immediately to the left of the or i ginal location ( as viewed from the front).
The unit will now return to monaural operation following a power failure.
Th i s change does not affect the stere-mono switching.
MONO SOURCE SELECTION
The stereo generator is normally shipped to utilize the left channel for mon-
aural transmission. To select the right channel, unsolder the center conductor
of the sh i elded cable (L) from the terminal immediately in front of the mono-
stereo selection relay K 1. In its place, solder the center conductor of the
companion (R) shielded cable.
NOTE: Both Land R cables must remain
in place and connected to termina l s L
and R
for proper channel be lance. In
case of a modification to right chan-
nel mono output, insure that the M pin
end of the unused cable does not
short.
REWIRING POWER TRANSFORMER FOR 240 V AC INPUT
The BTS -101A is norma ll y wired for a primary voltage of 120 V ac. The split-
primary power transformer, T101, can have its windings connected in series for
240 V ac input, as shown on the schematic. The transformer has been designed
for either 50 or 60 Hz operation. When the transformer is reconnected for 240
V ac operation, the fuse should be changed to one with a 1/8-ampere rating .
ALIGNMENT PROCEDURE
The internal adjustments are factory sealed to prevent changes due to vibration
during shipment, and should not normally require field adjustment. This align -
ment
procedure is provided in the event that component replacement or other
unusual conditions make realignment necessary .
TEST EQUIPMENT
The test equipment listed in the RECOMMENDED TEST EQUIPMENT list in the front
of this book is necessary for the alignment of the BTS-101A Stereo Generator.
It is very important that the test equipment be checked periodically for
accuracy of calibration.

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12
POWER SUPPLY CHECK
1. Apply power to the stereo generator and check t he de voltages at T P6 (gray )
and
TP7 (white). Refer to figure 4. The voltages should be plus and minus
24 volts, _::10% respectively.
2. Check the voltage regulators by testing the following points ( see figure
12):
A. The de voltage at U1 pin 7 should be 12 volts +5%.
B. The de voltage at U1 pin 4 should be -12 volts-+5 %.
C. The de voltage at U15 pin 14 should be 5 volts +5%.
AUDIO STAGE ALIGNMENT
1. Connect the left and right audio inputs in parallel and in phase and apply
a 2.45 volt rms audio signal at 21 22 Hz (equivalent to an L=R signal of +10
dBm).
2. Check that stereo generator is in STEREO mode (S101 to ST E RE O ), and set the
PILOT LEVEL control to off (R46 fully counterclockwise).
3. Set the audio amplifiers flat by switching out pre-emphasis networks
(switches S1 through S4 to left) and audio filters out (switches S5 and S6
up).
4. Set LEFT GAIN control (R7) for an output level of O dBV (0.775 V rms) at
TP3 (green).
5. Set right channel 150 Hz linear crosstalk control (R28) for a O dBV level
at TP4 (blue).
6. Reduce oscillator level until output at TP3 equals -3 dBV (0. 54 8 V rms).
Switch to left channel pre-emphasis networks (switches S1 and S2 to right)
and adjust LEFT PRE-EMPHASIS control (R15) until output at TP3 equals 0
dBV. Switch
out left pre-emphasis (switches S1 and S2 to left) and return
oscillator to original level.
7. Switch in left channel 15 kHz audio lowpass filter FL 1 (rear filter, switch
S5 down) . Set oscillator to 19 kHz. While monitorin g TP3 with an
oscilloscope;
A. Adjust inductor L4 for a null. See fi g ure 9.
B. Adjust L6 for a null at 22 kHz .
C. Adjust L2 for a null at 30 k!-lz .
D. Recheck 19 and 22 kHz adjustments . Switch left channel filter out
of the circuit (switch S5 up).
8. Move the scope to TP4 and switch in the right 15 kHz lowpass filter FL2
(front filter, switch S6 down) . Set the oscillator to 19 kHz and;
A. Adjust inductor L4 for a null.
B. Adjust L6 for a null at 22 kHz,

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13
C. Adjust L2 for a null at 30 kHz.
D. Recheck 19 and 22 kl-lz adjustments. Switch the right 15 kHz filter
out of the circuit (switch S6 up).
9. Disconnect the audio oscillato r from the generator inputs and connect a
sweep generator in its place.
A. Set the scope for external horizontal input and drive this input with
the control voltage output of the sweep gene rator. Set the sweep width of
the generator to cover the range of 200 Hz to 16 kHz, and set the sweep
rate to approximately 5 sweeps per second.
B. This step requires the use of a precision differential amplifier having
a common mode rejection ratio of approximately 80 dB. Such an amplifier
may be constructed as shown in figure 14. Connect the inputs of the pre-
cision unity gain differential amplifier to TP3 and TP4 and connect the
differential amplifier output to the vertical input of the oscilloscope.
C. Set the scope to 1 V/crn sensitivity; feed a left only reference signal
to the sweep generator, and adjust the output level of the sweep generator
to yield a 2 volts peak-to-peak signal on the scope.
Feed an L= R signal to the stereo generator and set the scope sensitivity to
5 mV/cm.
The scope now dis plays amplitude and phase errors ( between the two audio
channels) on the ve rtic al axis against frequency on the horizontal axis.
Adjustments will now be made which will reduce these errors to 5 mV peak-to-
peak (1 cm peak-to-peak) which is 52 dB below the reference level. It may
be necessary to decrease the scope sensitivity at the beginn in g of an ad-
justment but the displayed error should ultimately be below 5 mV peak-to-
peak (1 cm peak-to-peak on 5 mV/cm setting) .
Confirm that both pre-emphasis networks are switched out (switches S1
through S4 to the left).
10. Adjust right channel 150 Hz linear crosstalk control (R28) for minimum
amplitude on the scope during the mid and low-frequency portion of the
sweep. Adjust 15 kHz linear crosstalk (FLAT) capacitor C24 for minimum
amplitude at the higher frequencies.
11. This step requries that the sweep generator signal be de-emphasized.
Insert a suitable de-emphasis network, such as the one shown in figure 15,
between the sweep generator and stereo generator. Note that the de-
emphasis network shown is designed to work int o the 300 ohm impedance pre-
sented by the parallel connection of the left and right i nputs of the
stereo generator. Whenever this network is used to feed a single 600 ohm
input, that input should be paralleled with a 600 ohm resistor so that the
de-emphasis network always operates into a 300 ohm load.
Switch in the pre-emphasis networks of both audio channels (switches S1
through S4 to the right). Adjust right channel 1 500 Hz linear crosstalk
control (R37) for minimum amplitude at the mid-frequencies . Adjust right
channel 15 kHz linear crosstalk control (R35) for minimum amplitude at the
high frequencies.