RCA BTE-115 User manual

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Broadcast Equipment
BTE-115
FM
Exciter
Ml-561060
IB-8025256-1

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WARNI NG
VOLTAGES THAT ARE DANGEROUS TO LIFE ARE
INVOLVED IN THE OPERATION OF THIS ELEC-
TRONIC EQUIPMENT . OPERA TING PERSONNEL
MUST AT ALL TIMES OBSERVE ALL SAFETY
REGULATIONS. DO NOT CHANGE TUBES OR
MAKE ADJUSTMENTS INSIDE THE EQUIPMENT
WITH VOLTAGES APPLIED. DANGEROUS CONDI·
TIONS
MAY EXIST IN CIRCUITS WITH POWER
CONTROLS IN THE OFF POSITION 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
Personnel engaged in the installation, operation , or maint enance of this equi pm e nt 01 similar e qu i pment are urged to
become familiar with the following rules borh in th eory and practice. It is the duty of all operating personnel to be
prepared to give adequate Emergency Fir st Aid and thereby p1 event avo•dable loss of life.
1. Fi nd out 11 the person is
breathing.
You
must find out tf the person
has
stopped breathing. If you
think he is not breathing, place
him flat
on h is back . Put your
ear close to h is mouth and look
at his chest. If he is breathing,
you
can feel the air on your
cheek. You can see his chP.st
move up and down. If you do
not feel th e air or see the chest
move, he
is not breathing.
RESCUE
BREA TH ING
2. If he is no t, open th e airway by
tilting his head backward.
Lift up his neck w,111 one hand
and push d own on his forehead
with t he other. Th is opens th e
airway.
Somet imes do ing this
wi ll let the person b1 eathe aga i ll
by h im sel f. If 11 does not, begi11
rescue breathing.
BURNS
3.
If he is still not breathing, begin
rescue
br eathing:
K
ee p h is head tilted backwar d.
Pinch his nose shut.
Put you r mouth tightly over h is
mouth.
Bl ow i nto his mouth once every
five seconds.
Do
Not S top Rescue Brea th i ng
Until H elp Comes.
LOOSEN CLOTHING -KEEP WARM
Do this when the victim is breath -
H\g by himself or help is available.
Keep him quiet as possible
and
t, om becoming chilled. Ot herwise,
11
e~ t him for shock.
SKIN REDDENED: App ly ice co ld water to burned area
to preve
nt burn from going deeper into sk,n 1,s~u~.
Cover area wi th cl ean sheet or cloth to keep away <1 11.
Con sult a physician.
deepe1
into sk 111 tis sue . Cove, area with cl ean sheet or
cloth
to keep away air. Treat victim for shock and take
to hospita l.
SKIN BLISTERED OR FLESH CHARRED : Apply ice
cold
water to burn ed area to prevent burn f1 om 901119
EXTENSIVE BURN - SKIN BROKEN : Cover area with
cltia,1 sl1 ei:>t or t: lo th to keep away air. Treat victim for
shock ancl take
to hospita l.

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Instructions
BTE-115
FM Exciter
Ml-561060
-·
lit
•
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Commercial Communications Systems Division/Front and Cooper Streets / Camde n, New J ersey, U.S.A., 08102
PRINTED IN U.S.A.
IB-8025256-1

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I I
SAFETY PRECAUTIONS
This equipment is designed to fully safeguard all personnel from operating
hazards, Labels on the equipment and caut ion notices in the instruction book
clearly point out these potential hazards.
Any module or Printed Wiring Board may have hazardous voltages exposed,
50
cau tion must be exercised,
Follo w the recommended procedures provided in the I nstruction Book for care
and maintenance of the equipment,
Always replace the protective covers af t er servicing the equipment.
WARRANTY ITE MS
Particular parts and/or equipment covered by warranty are spec if ically stated as
such in the warranty or contract given to the customer at the time of sale. The
warranry or contract also stipu l ates the conditions under which the warranty
may be exercised,
To obtain a new replacement for such warranty items, contact your l oca l RCA
safes
office and please supp ly Product I dent ifi cation (including the Original In-
voice
Number, Ml Number, Type Number, Model Numbe r, and Serial Number)
and Replacement Pa rt Identification (including Stock Number and Description).
Reque sts for warranty rep l acements may be undu ly d elayed if all this in•
formation is not supp lied.
EQUIPMENT LOST OR DAMAGED IN TR ANS IT
When d••livP.r ing the equipment to you, the truck driver or carrier's agent will
present a receipt for your signature. Do not sign it until y ou have (a) inspected
the conta iners for visible signs of damage and (bl counted the containers an d
compared wi th the amount shown on the shipping papers . If a shortage or if
evidence
of damag e is noted, insi st that notat i on to that effect be made on the
ship ping papers before you sign them,
Further, after receiving the equipment, unpack it and inspect thoroughly fo r
concealed
damage. If concealed damage is discovere d, immediate ly notify the
carrier,
confirming the notification in writing, and secure an inspectio n report.
This item should be unpacked and inspected for damage WI THIN 15 DA YS after
receipt. R eport a ll shortages and damages to RCA, Commercial Communication
Systems Division - Camden, New Jersey 08102 .
RCA will file all clalms
for loss and damage on th is equipment so long as the
inspection report is obtained. Disposition of- the damaged ite m wi ll be furnished
by RCA.
FIELD ENGINEERING SERVICE
RCA Field Engineering Service is available at current rates. R equests for field
engineering service
ma y be addressed to your RCA Broadcast Field Represen-
tat ive or the RCA Servi ce Company, Incorporated -Broadcast Service Divis ion
- Camden, New Jersey 08102 . Te lephone [phone].
TECH ALERT
Emergency 24 hour telephone consultation service for technical prob l ems is
available. Call TECH ALERT at (6 09 ) 338-3434. Tel ex messages will be
forwarded to the addressee upon receipt. Western Union telex number is
83-4450 ,

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BTE-115 FM EXCITER SYSTEM OPTIONS
TECHNICAL SUMMARY.
GENERAL DESCRIPTION
DETAILED CIRCUIT DESCRIPTION.
Audio and Metering Module.
Modulated Oscillator .. .
RF Amplifier ...... .
High-Frequency Divider
..
Reference Oscillator and AFC
Power Supply
INSTALLATION ... ...... .
General . . . . . . . . . . .
Selection of a Mounting Position
TABLE OF CONTENTS
Drilling Holes ... . : . . ...... .
Interfacing the Exciter to the Transmitter
Control Circuits .......... .
AC Power Input to the Exciter System.
Exciter
RF Outputs.
Audio Input Signals
Final Mounting.
INTERNAL ADJUSTMENTS . . .
Power Supply ..... .
+13.5 Volt Adjustment
Maximum Power Set ..
Modulated Oscillator ..
Oscillator Frequency.
Distortion Adjust ..
Modulator Sensitivity
Buffer Tuning . ..
Amplifier Tuning ..
Buffer Calibration.
RF Amplifier ..
Input Tuning. .. .
Driver
Tuning .. .
Final
Tuning ... .
Forward Power Calibration.
Reflected Power Calibration
Reference
Oscillator and AFC .
Frequency Adjustment
......... . .... .
3125 Hz Tuning (Divider/Miscount Monitor Tuning}.
AFC Loss Idle Adjustment.
AFC/Defeat Switch
.......... .
Audio and Metering Module ........ .
Meter Zero. .
..... . ...... .
Wideband Gain Trim .......... .
Composite Modulation
Meter Calibration.
Total Modulation Meter Calibration.
SCA 1 Injection Meter Calibration .
SCA 2 Injection Meter Calibration.
Left Modulation Meter Calibration.
Right Modulation Meter Calibration.
Monaural Gain Trim .....
Monaural Mete~ Calibration.
Pre-emphasis Trim
Meter Damping ..... . .
V
vi
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IV
TABLE OF CONTENTS (Continued)
ROUT IN E OPERATION .
Meter Readings .
Power Adjustment
Frequency
Control
Indicators
RF Samp l es ....
PARTS ORDER I NG I NFORMATION
REPLACEMENT PARTS .
SUGGESTED EQUIPMEN T SPARES
Figure Title
A BTE-115 Front Panel
B BTE-115 Rear View
C
PW Board Locator
LIST OF ILLUSTRATIONS
D Modu l ated Osei l lat or PW Board
E Audio and Meter i
ng PW Board
F Power Supply PW Board
G
Reference Oscillator/AFC PW Board
H
RF Amp l ifier PW Board
I High Frequency Div i der PW Board
l BTE-115
FM Exciter, Block Diagra m
2
Main Frame, Schematic
3 Audio and Metering Board, Con trols and Adjustments
4 Audio and Metering B oard, Schematic
5 Modulated Osci l lator, Adjustments
6 Modulated Oscillator, Schematic
7 RF Amplifier, Adjustments
8 RF Amplifier, Sc h ematic
9 High Frequency Divider, Schematic (Early Models)
9A High Frequency Divider, Schematic (Later Models)
10 Reference Oscil later/AFC , Adjust ments
11 Reference Osci l lator/AFC, Schematic
12 Power Supply, Adjustments
13 Power Supply, Schematic
14 Audio LPF (Audio and Metering Boards), Schematic
15 Input Pad (Ma in Frame), Schematic
16 Audio and Mete ring Board, PWB L ayout
17 Modulated Osci l l ater, PWB Layout
18 RF Amp li fier , PWB Layout
19 H igh Frequency Divi der, PWB Layout
20
Reference Oscillator/AFC, PWB Layout
21 Power Supply, PWB L ayout
22 Aud io LPF, PWB Layout
23 I nput Pad, PWB Layout
24 Power
Di stribut ion PWB
25 I nterface Panel Schemat ic
26 Exciter System Layout and Template
16
16
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18
18
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23
32
Page
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BTE- 11 5 FM EXCITER SYSTEM OPTIONS
The BTE- 11 5 FM Exciter System is available in several forms as follows:
1. Mono
(A)
(B)
(C)
(0)
System, ES-560982, includes
1 Exciter, less audio LPF, 5 MHz crysta l and oven (Specify
1 5 MHz reference crystal and oven (Instal l ed in Exciter)
l Plu
g-in 15 kHz audio L PF for BTE-115
1 Con n ector, Audio lnout
frequency)
2.
Mono and l . SCA Sys tern, ES-560983, includes
(A) l Exciter, less audio LPF, 5 MHz crystal and oven (Specify frequency)
(B) 1 5 MHz reference crystal and oven (Installed in Exciter)
MI-56 1 060
Ml-561066
MI - 56 1 063
Ml-561067-1
MI-561060
MI-561066
V
(C) l BTX- 1 01 SCA generator less audio LPF (Specify freq. 41 or 67
(D) l Plug-in 15 kHz audio LPF for BTE- 11 5
kHz. std .) lo' 1-561062
(E) 1 Plug-in 5 kHz audio LPF for SCA unit
(F) l Interconnecting cable
3. Mono and 2 SCA System, ES -560984, includes
(A) 1 Exciter, less audio LPF , 5 MHz crystal and oven (Specify frequency)
(B) 1 5 MHz reference crystal and oven (Installed in Exciter)
(C) 2 BTX - 101 SCA generators, less audio LPF
(D) l Plug-in 15 kHz audio LPF for BTE-115
(E) 2 Plug-in 5 kHz audio LPF for SCA units
(F) 1 Interconnecting cable for BTE-115 Mono and 2 SCA systems
4. Stereo System , ES -560985, includes
!
A) l Exciter, less audio LPF, 5 MHz cr.ystal and oven (Specify frequency)
B) 1 5 MHz reference crystal and oven (Insta lled in Exciter)
C) l BTS-101 Stereo generator less 2 audio L PFs
D) 1 Plug-in 15 kHz audio LPF for BTE -1 15
(E) l Pair of plug-in 15 kHz audio L PF for BTS-101
(F) l Interconnecting cable for BTE-1 15 Stereo system
5. Stereo
and 1 SCA System, ES-560986, includes
(A) Ex citer, less audio LPF, 5 M Hz crystal and oven (Specify frequency)
(8) 1 5
MHz reference crystal and oven (Installed in Exci ter)
(C) 1 BTS - 101 Stereo gene rator less 2 audio LP Fs
(D) 1 BTX-101 SCA generator less audio LPF
(E) 1 Plug-in 15 kHz a ud io LPF for BTE-115
(F) 1 Pair of plu g-in 15 kHz audio LPFs for BTS-101
(G) l P lu g-in 5 kHz audio LPF for SCA unit
(H) 1 Interconnecting cable for BTE- 11 5 Stereo and l SCA system
6. Stereo and 2 SCA System, ES-560987, includes
(A) l Exciter, less audio LPF, 5 MHz crystal and oven (Spec if y
(B) l 5 MHz reference crystal and oven (Installed in Exciter)
(C) 1 BTS- 1 01 Stereo generator less 2 audio L PFs
(D) 2 BTX-101 SCA generator less audio LPF
(E) 1 Plug-in 15 kHz audio LPF for BTE-1 15
(F) 1
Pair of plug-in 15 kHz audio L PFs for BTS- 101
(G) 2 Plug-in 5 kHz audio LPFs for SCA units
(H) 1 Interconnecting cable for BTE-115 and 2 SCA sys tems
frequency)
MI-561063
MI-561065
MI-561067-2*
Ml-561060
MJ-561066
MI-561062
MI-561063
Ml-561065
Ml-561067 - 3*
Ml-561060
MI - 56 1 066
MJ-56106 1
Ml-561063
MI-561064
MI-56 1 06 7-4*
MI-561060
MI-56 1 066
MI-5610 61
MI-561062
MI-561063
Ml-561064
Ml-561065
Ml - 561067- 6
M1
-56106 0
MI-561066
M I-561061
MI-561062
MI-561063
MI-561064
MI-561065
Ml-561067-6
The followi ng optional items are available for use with the BTE-1 15 FM Exciter System:
l . Spare 5
MHz crystal and oven
5 MHz crystal only
crystal oven on ly
2.
Complet e set of connector pl ugs for the BTE-115 Exciter
3. Compl ete set of connector plugs for the BTX -1 01 SCA Generator
4. Complete set of connectors pl ugs for the BTS-101 St ereo Generator
5. Blank aluminum pa nel, 1-3/4"
6. Set of chassis s li des for servicing
7. Interface a nd Radiate Panel
8. Connector Kit for Interface Panel
9. Dri llin g Temp la te for mounting exciter system
*
tir
In some cases an MI-56 1067 Interco nn ect Cab le having a higher
dash number than that specified may be supplied.
Required only
when interface pa nel MI - 56107 1 and/or Interconnection
Cab le MI-561071 are not used.
MI-561066
M l-561066X
MI-561066A
MI -561068**
Ml-551070**
MI -561069**
MI - 561072
Ml-561073
MI-561071
Ml-563485
3742738

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VI
PERFORMANCE
Type of Emission.
Frequency
Range
TECHNICAL SUMMARY
(prograrrrnable in 50 kHz steps) . . ..
Power Output (adjustable from front panel).
VSWR. . . •
Output
Impedance.
Output Connector.
Frequency Deviation -
100 %modulation
Modulation Capability
Carrier Frequency Stability
Modulation.
MONAURAL OPERATION
Audio Input Impedance
Audio Input Level
(100 %modulation).
Audio Frequency Response (30-15000 Hz).
Harmonic Distortion
Intermodulation
Distortion. . . .
FM Noise Level (referred to 100% modulation).
AM Noise Level (referred to 100% modulation).
Pre
-e mphas is Network Time Constant. .
F3 and F9
87.5 to 108 MHz
4 to 17 watts
Ooen or direct short
• · 50 ohms
.Type BNC
±75 kHz
±100 kHz
±500 Hz max.
Direct carrier FM
600 ohms, balanced
+10 dBm ±2 dB , referred to 400 Hz
. . ±1.0 dB max.
.0.3 % or less
0.3% or less
- 70 dB
-60 dB
0, 25, 50 or 75 µs ec as desired
.
Type BNC
• > 5000 ohms resistive, unbalanced
WIDE BAND OPERATION
Input Connector
Input
Impedance
Input Level
3.5 VRMS nominal for 100 %modulation referred to 400 Hz
ELECTRICAL
Power Line Requirements
Combi ned line Voltage Variation and Regulation.
Power Consumption
MECHANICAL
Dimensions, inches (cm)
(overall):
Width
Height.
Depth
Weight, pounds (kg)
Altitude, feet (meters)
Ambient Temperature
.120,
208 or 240 volts,
single phase, 50/60 hertz
±10%
80 watts max.
19 (48 .3)
3-1/2 (8.9)
9 (22.9)
.
40 (18. l)
. . 7500 (2286) max.
-20°c to+ 7o
0c (-4F0
to+ 140°F)

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VI I
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1111
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00 11 h • w
FM f ll( ltr: fll ■ T E H 5
J6
Figure A. BTE-115 Front Panel
J5 QI
J8 J7
--- - ---- --
..,,_
-~ ":-1
-
,.
Fl
02
J2
J4 J3
---- -----~---- --'
Figure B. BTE-115 Rear View

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VI II
MODULATED OSCILLATOR
• •
•
•
REFERENCE OSCILLATOR/AFC
2K 0 47
RF AMPLIFIER
VI
HIGH FREQUENCY DIVIDER
Figure C. PW Board Locator
Tl
•
Cl
CRI

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1
GENERAL DESCRIPTION
As shown in figure 1, the BTE - 115 consists of six basic
assemblies; an audio and metering module, a modulated oscillator
module , an rf power amplifier module, two modules for automatic
frequency control, (the programmable HF divider and the reference
oscillator/AFC) and a power supply assembly.
The exciter will accept, as the primary modulating input,
either monaural audio or a composite stereophonic signal . In
addition, t he BTE - 115 will accept one or two FM subcarrier (SCA)
signals from an external subcarrier generator.
When the companion RCA stereo (BTS-101) or subcarr ier,
(BTX - 101) genera t ors are used, the metering system in the BTE -11 5
exciter will allow full metering of all important signal para-
meters.
All of the above - mentioned modulating and metering signals
are routed to the audio and metering module. The summed
modulating signals are passed on to the modulated oscillator ,
while the metering system ou tput is applied to the front - panel
meter.
The modulated oscillator module generates an on - frequency
signal at a power level of 200 milliwatts. The summed modulating
signal from the audio and metering module is applied to the
modulated oscillator module, as is a frequency-controlling
voltage from the AFC system . The outpu t from the modulated
oscillator module is applied to the rf power amplifier module.
Low - power samples of rf are applied to a front -pane l connector
and to the AFC system.
The rf power amplifier accepts the signal from th e modulated
oscillator module and amplifies it to the desired power level.
As with the modulated oscillator module, a low- power sample of rf
is rou t ed to a front-panel connector.
The AFC system consists of two modules. The first is a
programmabl e divider. The inpu t to this module is a sample of
the carrier - frequency modulated oscillator . The output of the
divider is 1562.5 Hz square wave. The second module in the AFC
system contains the r emainder of the circuitry required to main -
tain the carrier on th e correct frequency . This includes a 5 MHz
crystal oscillator of very high stability, dividers to develop a
second 1562.5 Hz square wave, and phase comparison and loop-
stabilizing circuitry . Sophisticated monitoring circuitry is
also included in this module to assure on-frequency operation .

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2
The power supply assembly includes electronic regulation of
all volta ges in the exciter as well as voltage adjustment for
control of power output .
The front panel of the BTE -115 has been simplified by the
elimination of all controls not needed for routine operation.
A single meter will measure all important ope rating parameters,
both de and ac. The AFC system is switch - defeatable, whereby
a front -p anel control will permit the operator to maintain the
exciter on the correct frequency.
The exciter power output is controllable from the front
panel , with a switch to cease radiation and a variable control
for level adjustment . Front panel samples of the modulated
osci llator and rf amplifier outpu ts, both at a level suitable
for direct connection to a typical modulation or frequency
monito r, are also available.
The rear of the BTE - 115 contains the necessary connections
for interfacing with the entire line of RCA transmitters, as
well as the external modulation and metering sample inputs from
the affiliated RCA stereo and SCA gene r at ors.
DETAILED CIRCUIT DESCRIPTION
AUDIO AND METERING MODULE
Program audio, preferably processed by a frequency -con scious
limiter, such as the RCA BA-147 or equivalent, is applied to pins
7 and 8 of the input connector, J4, on the rear of the BTE -115
exciter. From this connector, it is routed through the input
attenuator pad , to the audio · input transformer T2. After filter-
ing by inductor LB and feedthrough capacitor C9, it is routed to
the audio and metering module pin 1 . Refer to figure 4.
Resistor RlOl, in conjunction with potentiometer RlO2 and
resistor RlO3, terminate the input transformer. MONO GAIN TRIM
control RlO2 serves as a means of standardizing the modulation
sensitivity of the exciter in the monaur al mode. RlO4 and ClOl
provide on - board rf bypassing of the program signal. UlOl, biased
by RlOS, RlO6 and RlO7, provides audio signal amplification and
pre - emphasis. Low-frequency gain is set by the ratio of RllO to
Rll4, while Rll3 and capacitors ClO8 and ClO9 provide phase
correction for low-frequency square -wa ve transmission. The pre-
emphasis time-constant is determined by the sum of resistor Rlll
and PRE-EMPHASIS TRIM control Rll2 operating in conjunction with

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capacitors Cl04 and ClOS. Cl04 and Cl05 may be individually
switched in or out of the circuit to allow flat, 25, SO or 75
microsecond pre-emphasis . Rl09 and Cl07 provide phase compensa-
tion for UlOl.
3
The output of this stage is applied via terminating resistor
Rll5 to the audio lowpass filter. The filter may be bypassed
wi th switch S104. The filter output is applied t o the summing
amplifier s tage, Ul02 . Resistor Rll7 t e rminat es the audio low-
pass filte r. Capacitor Cll4 pr ov ides a sample of the audio to
MONO CAL potentiomete r Rl52. Amplifier Ul02 is biased by Rl25
and Rl26. The output of this summing amplifier is applied via
decoupling resistor Rl29 and inductor LlOl to the modulated
oscillato r module. A sample of this same signal is applied to
the TOTAL CAL potentiometer Rl30.
FM subcarrier signals, such as those from the RCA BTX.-101,
are applied to the summing amplifier via resistors Rl21 and Rl23.
Samples of the subcarr'iers are applied to SCA 1 INJ. CAL and
SCA 2 INJ. CAL potentiometers Rl22 and Rl24.
When ope ratin g in the stereophonic mode, an external stereo
signal, such as from the RCA BTS-101, is applied via the rear -
panel COI'1POSITE INPUT connector Jl and rf filtering with Ll and
C2 to the audio and metering module pin 7. A sample of thi s
composite stereo signal is applied to the COI'1P CAL potentiometer
Rl20 as well as to the series resistor Rll8. In the monaural
mode, the load side of Rll8 is shorted to ground by MONO-COMPOSITE
switch S101 and operation is in the monaural mode. In the stereo
mode, the output of the audio lowpass filter is shorted ou t by
S101 while the composite stereo signal is allowed to pass via
Rll8 and Rll9 to the summing amplifier, Ul02.
The gain of the summing amplifi er in the stereo mode is set
by the ratio of Rl27 and Rl28 t o Rll8 and Rll9 . WIDEBAND GAIN
TRIM potentiometer Rl28 provides a means of standardizing the
gain of this amplifier such that a 3.5 vo l t peak-to - peak composite
stereo signal at Jl provides 3.5 volts peak-to-peak at the output
of Ul02.
One metering sample is selected by the front-panel meter
switch Sl. This sample is routed t o the audio and metering
module pin 13. On-board rf filtering is provided by Rl32 in
conjunction with Cll8. QlOl and Ql02 provide push-pull signals
to the full-wave rectifier using Ql05 and Ql06. Ql04 provides
temperature-sensitive forward bias for the rectifiers. The
rectifiers charge Cl25 to the peak value of the signal in question.

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4
Rl44 determines the meter fall time . UlO3 provides the necessary
high impedance load for the rectifiers and low impedance source
necessary to drive the meter movement. Cl27 and Cl28, with Rl48
and Rl51, provide meter acceleration. Additional acceleration,
adjustable to provide critical damping , is provided by Rl46 and
Rl47 together with Cl26 and Rl45. The meter movement is connected
to pins 14 and 15 of this module whenever this metering system is
in use.
MODULATED OSCILLATOR
The surmned total modulating signal (monaural or stereo, plus
optional subcarriers) is applied to the modulated oscillator
module pin 1. Refer to figure 6. The standard signal level at
this point is 3. 5 volts peak-to - peak total for 100% modulation.
R2O1 and C2O1 provide on-board rf bypassing to the modulating
signal. The sensitivit y of the modulator is adjustable with
R2O2, M:lDULATOR SENSITIVITY, whose range is limited by R2O3.
Modulation of the oscillator is accomplished by the voltage - vari-
able capacitor CR2O3. This capacitor is reverse-biased by R2O6
and R2O8 . CR2O3 is coupled into the oscillator circuity via
fixed capacitor C2O8 and variable capacitor C2O7, DISTORTION
ADJUST.
Also connected to the oscil l ator circuit is a second
modulator using voltage - variable capacitor CR2O2 . The effective
capacity of this element is determined by the voltage applied to
pin 3 of this module. CR2O2 is coupled into the oscillator
circuitry with C214. The modulated oscillator itself is formed
using transistor Q2O1 and associated components. This is in a
Hartley configuration operating at carrier frequency with biasing
provided by R21O and R211; collector curren t is limited by R212.
The basic tank circuit is formed by inductor L2O4 and capacitors
C2O9, C21O, C211 and C218.
The output of the oscillator is applied to buffer stage
Q2O2. This stage is biased by R215 and R217; R219 sets the
collector current. This is a tuned amplifier with C225, L2O8 and
C226 determining the bandpass .
Both of these stages are supplied power by on - board
regulator U2O1. The output of this regulator is set to about
9 volts as determined by R222 and R223.
The output amplifier of the modula t ed oscil l ator module
utilizes transistor Q2O3 and associated components . This s t age
operates withou t forward bias. It is tuned by L211, C231 and
C232.

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5
Most of the output from Q203 is applied to the rf power
amplifier via pin 7 of the modulated oscillator module. A
lesser sample is applied to the front-panel test connector via
the resistive at t enua t or formed by R229 and R230. Another sample
is applied to the programmable high-frequency divider via C235
and R231. A final sample is applied to rectifier CR204. The
output of this rectifier is applied to the BUFF CAL potentio me ter
R234.
RF AMPLIFIER
The on-frequency carrier from th e modulated oscillator module
is applied to the input of the rf power amplifier. Refer to
figure 8 . The input to this amplifier is tuned by C301, L301 and
C302. The first stage, utilizing Q301, operates class C. It is
tuned by C308, C309, C310 and L305.
The second stage, Q302, also operates class C. It is tuned
with L309, C317 and C318 . Harmonics are removed by a fixed - tuned
lowpass filter using C319, 1310, C320 through C324, L311 and 1312.
A directional coupler provides front - panel indications of forward
and reflected power .
HIGH - FREQUENCY DIVIDER
A
sample of the rf from the modulated oscilla t or module is
applied to pin 4 of this module . Refer to figure 9 . Here, it is
amplified by Q401, Q402 and Q403. Q401 operates nearly class A;
is biased by R402 and R401, and collector current is determined
by R403. The second stage operates in a similar manner using
R407 and R406 for biasing and R409 for col l ector current deter-
mination . The third stage using Q403 is used for level trans-
latio~ into integrated circuit U401. Q403 is forward biased and
temperature - compensated by CR.401, which has a current through it
via R411. Integrated-circuit divider U401 divides the carrier
frequency by four; its output is a square wave at one-quarter of
the carrier frequency, regardless of frequency.
The output from U401 is applied to a second divider using
part of U407 . This divider ' s input is at pin 6 and its output,
divided again by four to one-sixteenth of carrier frequency, is
at pin 2.
The output from U407 pin 2 is applied to a series of dividers
whose division ratio can be controlled by means of straps.
Referrred to as programmable dividers, as implemented in this

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6
design, they can divide by any division ratio between 1770 and
2158. This will accommodate any carrier frequency from 87 . 5 to
107.9 MHz. The outputs from these four dividers are applied to
a four - input gate using U406. The output from this gate, which
is a narrow pulse at a fixed rate of 3125 Hz, is applied to a
second part of U407 for further division to a square wave of
1562.5 Hz. Regardless of the carrier frequency chosen, the
output from this module will be a square wave at 1562.5 Hz. This
square wave is routed via inductor L402 to the other module in-
volved in the automatic frequency control system, the reference
oscillator and AFC module . The output from U407 is also avail -
able via pin 7 to the front-panel meter switch HF DIV position.
REFERENCE OSCILLATOR AND AFC
A very stable 5 MHz signal is gene rated by the reference
oscillator using Q501. See figure 11. Unlike other exciters
which are rated over a limited temperature range, the reference
oscil lat or in the RCA BTE-115 is not only temperature compensated,
but is controlled by an efficien t proportional control crystal
ove n. The combination of these techniques, together with the use
of a field-effect transistor, provides excellent frequency
~tab ility ove r the full -20° to +70° C range. The load for QSOl
is R503. C503, the crystal, CSOl and C502 form a Pierce
oscilla tor. CSOl, FREQ, is used to vernier the frequency of the
5 MHz signal. All of the sensing and driving circuitry for the
oven is self - contained as a part of the oven assembly.
A sample of the 5 MHz oscillation is applied to buffer QS02
via resistive divider R504 and R505. Q502 is used to interface
to the digital circuitry, with its output coupled to integrated
circuit U501. The ou tput of USOi is a 5 MHz pulse. This 5 MHz
sig nal is subsequently divided down to a frequency of 1562.5 Hz
by integrated circuits U502 through U505. The output of U505 is
available via pin 6 to the front-panel meter switch L F DIV
position.
The 1562.5 Hz square wave from the 5 MHz reference oscillator
is also routed to pin 5 of USOl. The 1562 . 5 Hz square wave
signal from the programmable divider module is rout ed to USOl,
pin 4, via module pin 5. USO l is used as a phase detector. Its
output is a signal at a repetition rate of 3125 Hz, and a duty
cycle that varies from 0% to 100 %, dependent upon the phase error
between the divided-down carrier and the divided-down reference
oscillator.

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The ou tput of U501 is applied via resistive divider RSl0 and
RSll to amplifier stage Q503 . The output from this amplifier is
a waveform similar to that from US0l save for a much higher
amplitude. This signal is applied to three different circuits;
the automatic frequency control system, a loss - of -l ock system ,
and a unique divider/miscount monitor.
The automa t ic frequency con trol system accepts the signal
from the collector of Q503 and first passes it through a 60 Hz
lowpass filter. The resultant de signal is then applied to a de
amplifier, with U507 and associated components. The output from
this stage is applied to the modulated oscilla t or modu le frequency -
controlling input; it is also available via pin 9 to the front-
panel meter switch AFC position.
Should the AFC system lose lock, there will be a low-frequency
ripple riding on the output of the signal from QS03 . This signal
is extracted by the 250 Hz lowpass filter using U509 and associated
components .
Comparator USl0 generates a single pulse at its output for
each cycle of the previously - mentioned low-frequency ri pple .
This pulse is rectified by CR504 and is used to charge C532 via
R542 . The resulting de is used to opera te Darlington transistor
pair Q505 and QS06. This excites the loss-of - lock relay Kl via
terminal 11 .
Should the carrier - frequency oscillator, the reference
oscilla tor or any of the dividers fail, or shou ld any stage mis -
count, then the 3125 Hz signal at the collector of Q503 will
disappear. The tuned amplifier stage composed of U508 and its
associated circuitry monitors the presence of this 3125 Hz tone.
The out put of U508 is coupled via capacitor C526 t o the rectifier
circuit involving CRS0l, CR502 and capacitor C527. When the
sys tem is functioning correctly, a de voltage will be developed
across CS27 . This voltage is applied via R534 and R535 to
transistor QS04, which is normally kept in saturation; the
voltage at its collector is low.
Should any of the previously - mentioned oscillator or divider
failures occur, the voltage at the collector of Q504 will rise,
allowing CR503 to charge capacitor C532. This will energize the
l oss -lock relay Kl.
It should be noted that, when the front - panel AFC-DEFEAT
sw itch is operated to the DEFEAT position, relay Kl is made
inoperative. In addition, a substitute AFC voltage is applied

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8
t o the modulated oscillator module . This substitute voltage is
derived fr om the front - panel :MANUAL FREQUENCY ADJUST poten t iometer,
enabling the operator to set the carrier frequency regardless of
any AFC system failure.
POWER SUPPLY
All of the circuitry in the BTE - 115 operates from precisely
regulated power supply voltages . These are derived from a bridge
rectifier supplying primary unregulated power to a single counter-
grade filter capacitor. Refer to figure 13. The normal voltage
across this capacitor is about 20 volts de . It is applied to a
series of regulators for the various circuits. All of the
digital integrated circuits are powered by a 309- type regulator
whose output is 5 volts de. Most of the remaining circui t ry is
regulated by a 723-type integrated circuit (U601) operating in
conjunction with PNP transistor Q601 and NPN series pass transistor
Ql. The output of this regulator system is adjustable by means of
+13.s V ADJ potentiometer, R607 , whose range is limited by R606
and R608. Current sensing for short circuit protection is provided
by R604. An adjustable voltage is provided by a second regulator
using U602 and Q2. This regulator provides a front-panel variable
voltage for the rf amplifier as a means of adjusting the power
output. The front-pane l RF OUTPUT LEVEL control has its range
restricted by the internal MAX SET control, R617. R615 provides
current sensing for short circuit protection .
INSTALLATION
G ENERAL
This procedure covers installation of the BTE- 1 15 Exciter in the follow-
ing
RCA transmitters:
BTF-3ES1
BTF - 5ES2
BTF - 5ES1
BTF - lOESl
BTF - 20ES1
Referred to in text as BTF -3/5
Referred to in
text as BTF -5/10/20
This procedu
re specifies use of the optional MI-561071 Exciter/Transmitter
Interface an d Radiate Pa n el. This panel provides acoutlets for connection of
the Exciter Un it (and Stereo and SCA Generator) Power Cord(s), and also contains
a
re lay wh ich deactivates the Exciter RF Power Amplifier when the main trans-
mitter is sh ut down.

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9
Although this procedure applies to the above mentioned transmitters, it
can general ly be applied to other FM transmitters as well.
In addition to the Exciter Unit and Interface Panel, the Exciter System
may include a Stereo Generator and one or two SCA Generators. Provisions for
mounting these are covered below. Comp l ete installation instructions for
these units are included with the instruction manuals supplied with the units.
SELECTION OF MOUNTING LOCATION
A complete Exciter System (Exciter, Interface, Stereo Generator, 2
SCA Generators) requires 10 1/2 inches (26.7 cm) of rack mounting space in the
transmitter. A drilling template, drawing no . 3742738, is ava ilable with the
Exciter which shows the required mounting holes, and the location of the
various
units within this 10 1/2 inches (26.7 cm). Blank panels are mounted
in place of equipment not used.
In the BTF -3/5 transmitter, the Exciter System is located in the 10 1/2
inch
(26 .7 cm) space provided near the center of the transmitter rack. In
the BTF-5/10/20 transmitter, the Exciter System normally mounts in the 10 1/2
inch
(26 .7 cm) space provided between the blank panels in the lower left side
of the transmitter (as viewed from front).
However , if the optional slider rails are used with the Exciter
System, the Exciter
may have to be relocated to prevent interfere nce between
the sliders and other components in the BTF-5/10/20 transmitter. Refer to
separate instructions supp lied with the slider rails for details.
DRILLING HOLES
Using the rack template, mark, then drill and tap the #10-32 holes, if
they are not already provided . These holes will be needed in all cases, since
they will
be used to mount either the appropriate unit, or a blank panel. In
transmitters that are already drilled for the older RCA BTE-15A Exciter System,
the bottom (3)
of the (4) existing tapped holes will line up with tapped holes
specified by the template.
The counter bored holes may not be required. They are used primarily
to mount the optional slider rails to the cabinet, and should be drilled for
all units to be equipped with slides. In systems utiliz i ng the stereo or
SCA generators, these holes are used to mount the system interconnecting cable
to the cabinet. In this case, one counter bored hole at each unit l ocation,
on the left side only (as viewed from front) should be sufficient for securing
the cable.
INTERFACING THE EXCITER TO THE TRANSMITTER
It is recommended that the Exciter and Interface Panel be temporarily
mounted or held in place so that the ultimate location of the various con-
nectors can
be determined. Wiring is then accomplished as follows:

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10
Control Circuits
Connections are made to the 4 pin plug (5Jl) located on the
Interface/Radiate Panel. A normally closed
set of contacts is provided
between pins 1 and 2 of this connector. These contacts open upon
failure of the AFC circuit in the Exciter, providing a shut down signal
to the transmitter . 220 volts ac is required between pins 3 and 4 of
this connector when rf output is required from the Exciter. Absence of
thi·s voltage when the main transmitter is shut down de-energizes the
interface board relay, resulting in removal of power from the exciter
rf amplifier, reducing power consumption by the exciter while maintain-
ing
it in a state of readiness.
If the t,ransmitter is already equipped with the mating four pin
plug, proceed to
AC POWER INPUT TO THE EXCITER SYSTEM, below. Otherwise,
proceed as follows:
A. BTF-3/5 Transmitter - Remove existing plugs from control wires.
Connect
to 4 prong plug (supplied as Interface Panel Connector
Kit
MI -563485~item 2) as follows:
Wire
# To Pin #
86
l
87
2
42
3
43 or 330
4
B. BTF-5/10/20 Transmitter - Remove existing plugs and associated
cable harness
from 1TB6 and 1Z8. Remove the 4 wires specified
from this cable and connect to 1TB6 and the 4 prong plug
li~d as
Interface Panel Connector Kit MI-563485, item 2) as
Wire#
508
509
500
501
From
lTB6-9
1TB6- l0
1TB6- l
lTB6-2
To Pin#
l
2
3
4
Retain remainder of cable for possib le use with Stereo or SCA
Generators.
AC Power Input to the Exciter System
117 volts ac is applied to the twist-lock connector on the Inter-
face Panel. From there it is distributed via the four standard con-
venience
outlets provided for the exciter, stereo generator, and SCA
units.
If transmitter is already equipped with the proper mating plug,
proceed to
EXCITER RF OUTPUT, below. Otherwise, proceed as follows:
A. BTF-3/5 Transmitter -Connect mating twist-lock plug (supplied
with the
transmitter as MI-561012. Item 5) to the 117 volt ac
power source, usinq suitable three wire cable.