RCA BTE-10B User manual

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INSTRUCTIONS
BTE-108
Direct
FM
Multiplex
Exciter
ES-27278
LIST
OF
EQUIPMENT
BTE
-10B
FM
Exciter (ES-
27278)
Description
Quantity
1
FM
Exciter
Unit
. . . . . . .
....
.
..
.
..
...
. .
...
. . . . . . . .
..
...
....
. . . .
Crystal
Unit
(Spare
to be
ordered
separately)
....
.
..
. . .
.............
.
Set
of
Operating
Tubes
..
. . .
....
.........
. .
..
.........
... ...
.
....
.
Set
of
FCC
Spare
Tubes
(N
ot
supplied
-
co
be
ordered
separatel
y)
....
. . .
2
Instruction
Books
* See cable
of
crystals
and
frequencies.
Description
Capacitor,
ceramic, .01
µf
Capacitor,
feed
thru
-.00 l
µf
Capacitor
, ceramic, 5
µµf
Capacit
or, ceramic, 2,200
µµf
Capacitor,
ceramic,
10
µµf
Crystal
diode,
1N34A
Lamp,
neon
Fuse, 0.5
amp
Mount,
shock
mount
* 5-
minimum
quantity
shipped
.
RECOMMENDED SPARE PARTS
Symbol
Cl0
6,
Cll
3,
Cll
4,
Cll5,
Cl22,
C
l24,
Cl26,
Cl
30,
C
l32,
C
l3
5,
Cl38, Cl40,
Cl4
5,
Cl52, Cl53, Cl57,
Ct69,
Cl
72
,
Cl80,
Ct8
4, C209, C211, C212
CI07,
Cl20,
Cl27,
Cl29,
Cl31,
Ct34,
Cl43,
Cl44,
C
l46
,
Ct
47,
Ct50
,
Ct66
Cl
33,
Cl55,
Cl56
C
l48
C214,
Cl71,
Ct
77,
Ct8
3, C207, C208,
CI09,
Cll0,
Cl
49, C
l60,
Cl6
4
CRI0I,
CR102, CR104
DS!0l,
DS102
Fl0I,
F102
Reference
MI-34501
MI
-34509*
Ml-34510
IB-30262-1
E-1
Quantity
Stock
No
.
5 73960
5 99177
5* 77688
779
53
5* 77865
2 59395
5* 101857
2 212327
57692

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E-2
0
)
••••••••
••••e, ,. .•
••••••••
••••••••
·· ~ ••11••
.. •• -' ••
~ 0
FIHAI.Mo'IP
c., T\IMllilt
0
92203
Figure E-1. BTE-108 FM Multiplex Exciter

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E-3
TECHNICAL SUMMARY
ELECTRICAL CHARACTERISTICS
Type-of Emission
Frt-quency Range
Power Output
Output Impedance
Frequency Deviation for 100'7, mod .
Modulation Capability
Carrier Frequenl"y Stability
Audio Input lmpedanl"e
Audio Input Level (100% mod.)
Audio Frequency Response 00-15000 l"ps)
Harmonil"
Distortion 00-15000 l"ps)
Fl\! Noise Level (referred to I00 o/c, FM mod.) .. .. . . . . .
AM
Noise Level (referred to carrier voltage)
Suh-carrier Input Level (30% mod . of carrier)
Sub-carrier Input Impedance ...
Sub-carrier Center Frequency Range
Main-to-Sub-channel Crosstalk ...... . . .. . . .
F.,
88-108 mt-/,
10 wall,
50 ohms
± 75 k(/s
± 100 kc/s min.
± 1000 cps max.
600/ 150 ohms
+ 10 ± 2 db 'm'
± I
db max.'
0. 5% max."
-
Gs db max.
-50
db max.
5v n1ax.~
10,000 ohms
. ,o to 67 kc/s
- 55 db '
Sub-to-Main-t·hannel
Crosstalk , .... . .. . . .. .. . . . . . . . . . . ..... .... . . . . . -65
db "
Power Line Requirements ..
Slow Voltage Variations
Power Consumption
Crystal Heaters
Altitude
Ambient Temperature Range
MECHANICAL SPECIFICATIONS
Overall Dimensions . . .
Weight
'Level measured at input (J IO I) using 400 cps tone .
'Audio frequenq • response referred to 75 µs pre-emphasis
curve.
"Distortion includes all harmonics up to 30 kc/s and is
measured following a standard 75 µs de-emphasis network.
' Subcarrier modulation percentage can be brought to 50%
if required. (See Subcarrier Modulation in text.)
240/208 or 117 V, single phase 50/60 cps
± 5%
300 wa11s, Approx.
I 17 volts, 50-60 cps, IO walls each
7500 ft.
max .
-20 °C to +45°C
Height
24½ "
80 lbs.
Width
19"
Depth
11"
' Referen(e shall be ± 7. 5 kc/s deviation of the suhcarrier
by a 400 cps tone. Main channel modulation 70% by
50-15000 cps tones.
''Reference
shall be ± 75 kc deviation of the main carrier
by a 400 cps tone . Sub-channel modulated JOO% ( ± 7.5
kc/s) by 30-6000 cps tones. Subcarrier modulated 30%
on main carrier.
TUBE COMPLEMENT
Symbol Type
Function Symbol Type Function
VlOl
6AQ5 Reactance Modulator
Vl09
6AH6
Frequency Divider
(1/4)
V102
6AQ5
Reactance
Modulator
VllO 6AH6
Frequency Divider
(1/4)
Vl03 6AQ5
Master Oscillator
Vlll 6AH6
Frequency Divider
(1/5)
Vl04 6CL6
Subcarrier Modulator
Vll2 6AU6 Crystal Oscillator
Vl0S
5763 Frequency Tripler
Vll3
6AH6 Crystal Frequency Divider (1/5)
Vl06
5763 Frequency Tripler
V114 12AT7 Cathode Follower
V115 6AS6
Off-Frequency Detector
V107
6146
Frequency Doubler and
v116
2D21
Off-Frequency Control
Power Amplifier
Vll7 OD3
Voltage Regulator
V108
6AH6
Frequency Divider (1/3)
V118 lEPl Cathode Ray Tube

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E-4
DESCRIPTION
The
RCA BTE-10B, ES-27278,
is
a frequency mod-
ulated exciter which provides an r-f
output
of
ten
watts
at
any specified frequency in the 88 to 108
megacycle band.
The
compact
unit
incorporates a
subcarrier
modulator
stage which can be fed
from
a subcarrier
generator
such
as
the RCA
BTX-
IA to
provide for
multiplexing
one
or
two subcarriers
on
the main
FM
channel. Thus,
it
is
designed especially
to provide for various applications
of
FM multiplex
such
as
ba
ckground
music, and, if it
should
become
authoriz!!d, stereophonic sound.
The
BTE-10B
is
the exciter used in the RCA
BTF-5B
5KW
FM
Transmitter.
It can be used to
replace the exciter units
of
previous RCA FM trans-
mitters,
or
that
of
any ocher FM
tran
smitters where an
exciter
power
output
of ten watts
is
a
dequ
ate.
The
unit incorporates features which make it easy
co
adjust, easy to
maintain
a
nd
very reliable in operation.
All r-f multipliers,
including
the
output
stage, em-
ploy single-tuned circuits.
The
exciter can be housed
in a
standard
cabinet rack
together
with
a subcarrier
generator.
Employing
miniature
tubes
throughout,
the BTE-10B
is
a self-contained unit
with
built-in
power supplies and an oscilloscope
co
facilitate
alignment.
The
BTE-10B
when
properl
y adjusted,
and
used
fn
conjunction with the BTX-1 A Subcarrier Gener-
ator, will
provide
subchannel
perforn
~a
n
ce
compa-
rable
to
the main
FM
channel
_with
regard
co
signal-
co
-noise ratio
and
distortion.
The
frequency response
of
the subcarrier will be somewhat limited when
programming
the subcarrier separately.
R-f
multiplier
and
power
amplifier stages
of
the
BTE-108 use relatively
broadband,
single-tuned
or-
cuits, thus simplifying
adjustment
. A
built
-i
n
meter
can be switched to read the
following
voltages a
nd
currents:
Modulator
cathode current; second
and
third
multiplier
grid
currents; PA cathode and
plate
current;
AFC
control voltage;
and
plate voltage.
The
monitor
oscilloscope
incorporated
in the
ex
-
citer simplifies
adjustment
and
maintenance
of
the
AFC
frequency dividers. A switch permits instan-
taneous checking
and
adjus
tment
of
a
ll
five dividers,
and
a check
of
the control action
of
the phase
detector. Displays are in the
form
of
Lissajous' fig-
ures, with the advantages
th
at
lock-in
of
the
divider
s
can be observed easily. Checks can be
made
during
operation
without
disturbing
the
AFC
circuit in any
way.
This
type display requires no synchronization
or
o
ther
adjustments.
Power
supplies employ semiconductor rectifiers.
The
high
voltage regulated supply which furnishes
d
-c
plate
and
screen voltage utilizes a
bridge
type
germanium
rectifier.
Modulator
and
oscillator fila-
ments are
supplied
by a d-c supply
employing
a full
wave silicon rectifier.
All
components
of
the BTE-10B are
mounted
on
a vertical chassis. Special hinge-type'
mounting
pins
at
the bo
ttom
corners
permit
the
top
of
the chassis
to be
swung
out
for
access
co
the
wiring
and
circuit
components
on
the
underneath
side.
CIRCUITS
A block
diagram
of
the BTE-10B Exciter
is
shown
in Figure
2.
Circuits consist of: A master oscillator
which operates
at
I/18th
of
the
carrier frequency;
two reactance
modulators
to
provide
modulation
for
the main
channel;
a
third
reactance
modulator
for
the subcarrier; three frequency
multipliers
including
the
output
stage to
bring
the
output
frequency up to
the 88 to 108 me range; automatic frequency control
circuitry;
and
power
supplies to furnish a-c
and
d-c
voltages
for
these stages.
The
master oscillator
is
a 6AQ5
Hartley
type
oscillator which operates
at
a frequency between
approximately five
and
six
me.
,
depending
upon
the
desired
output
frequency.
The
plates
of
the two
6AQ5
reactance modulators
are
connected to the
oscillator
plate
,
and
the grids, which
are
in push-
pull, are inductively coupled to the place tank. R-f
voltages
on
the two
modulator
grids
are
180 degrees
out
of
ph
ase with respect to each other,
and
each
is
90 degrees
out
of
phase with the oscillator place.
Thus, one tube appears as a capacitive reactance and
the
other
appears
as
an inductive reaccance across the
oscillator tank.
The
magnitude
of
the reactive com-
ponent
presented to the
tank
coil varies
with
the
audio voltage applied to the
modul
a
tor
grids,
and
the frequency
of
the oscillator
is
varied accordingly.
The
mean frequency
is
controlled
by the bias voltage
applied
to one grid.
This
bias
voltage
is supplied
by the
automatic
frequency control circuit to be
described in a later
paragraph.
The
third
reactance
modulator,
an RCA
Type
6CL6, provides
for
modulation
of
the subcarrier
on
the main r-f ca
rrier
. This reactance tube
is
coupled
to
on
ly a
part
of
the oscillator coil since the required
deviation
of
the r-f carrier
by
the subcarrier
is
small.
Use
of
the
pushpull
modulator
and
the inductive
coupling
circuit results in a highly linear operation

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E-5
BTE-108 EXCITER CRYSTALS
Ml
No.*
Carrier Crystal
Ml
No.*
Carrier Crystal
Frequency (
MC)
Frequency
(KC)
Frequency (
MC)
Frequency
(KC)
34509-1 88.1 101.9676 34509-51 98.1 113.5417
-2
88.3 102.1991 -52 98.3 113.7731
·3
88
.5 102.4306 -53 98.5 114.0046
-4 88.7 102.6620 -54 98.7 114.2361
-5
88.9 102.8935 -55 98.9 114.4676
-6 89.1 103.1250 -56
99
.1 114.6991
-7
89
.3 103.3565 -57 99.3 114.9306
-8
89
.5
103.5880 -58 99.5 115.1620
·9
89.7 103.8194
-59
99.7 115.3935
-10 89.9 104.0509 -60
99.9
115.6250
-11
90.1 104.2824 -61 100.1 115.8565
-12
90.3 104.5139 -62 100.3 116.0880
-13 90.5 104.7454 -63 100.5 116.3194
-14
90.7 104.9769 -64 100.7 116.5509
-15
90.9
105.2083 -65 100.9 116.7824
-16 91.1 105.4398 -66 101.1 117.0139
·17
91.3 105.6713 -67 101.3 117.2454
-18
91.5 105.9028 -68 101.5 117.4769
-19 91.7 106.1343 -69 101.7 117.7083
-20 91.9 106.3657 -70 101.9 117.9383
-21 92.1 106.5972 -71 102.1 118.1713
-22
92
.3 106.8287 -72 102.3
118.4028
-23
92.5
107.0602 -73 102.5 118.6343
-24 92.7 107.2917 -74 102.7
118.8657
-25 92.9 107.5231 -75 102.9 119.0972
-26 93.1 107.7546 -76 103.1 119.3287
-27 93.3 107.9861 -77 103.3 119.5602
-28
93.5 108.2176
-78
103.5 119.7917
-29 93.7 108.4491 -79 103.7 120.0231
-30
93.9
108.6806
-80
103.9 120.2546
-31
94
.1 108.9120
-81
104.1 120.4861
-32 94.3 109.1435
-82
104.3 120.7176
-33
94.5
109.3750 -83 104.5 120.9491
-34
94
.7 109.6065
-84
104.7 121.1806
-35 94.9
109.
8380
-85
104.9 121.4120
-36 95.1 110.0694 -86
105.l
121.6435
-37 95.3 110.3009 -87 105.3 121.8750
-38
95.5 110.5324 -88 105.5 122.1065
-39
95.7 110.7639 -89 105.7 122.3380
-40
95.9 110.9954 -90 105.9 122.56~4
-41 96.1 .111.2269 -91 106.1 122.8009
-42 96.3
111.4583
·92 106.3 123.0324
-43 96.5 111.6898
·93
106.5 123.2639
-44
96.7 111.9213 -94 106.7 123.4954
-45
96.9
112.1528 .95 106.9 123.7268
-46 97.1 112.3843 -96 107.1 123.9583
-47 97.3 112.6157 -97 107.3 124.1898
-48
97.5
112.
8472
-98
107.5 124.4213
-49 97.7 113.0787 -99 107.7
124.6528
-50
97.9 113.3102
-100
107.9
124.8843
• Suffixes 1
to
100
designate
channel
number.
Add
200
to
1uffix
to
get
FCC
channel
number,
e.g., Ml-34509-75
designates
FCC
channel
275, frequency 102.9 me.

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E-6
MAIN
CHANNEL
AUDIO
INPUT
~---~
MODULATOR-OSCILLATOR
6AQ5
MOD
-,
I
I.-----.
7
I
~~I
RF
PRE-
EMPHASIS
NETWORK
6AQ5
5763
FREQ
5763
FREQ
TRIPLER
OUTPUT
6146
DOUBLER1+----<
MASTER
osc I
TRIPLER
PA
88-108
MC
._____,I
30 -
15,000
CPS
INPUT
FROM
6AQ5
MOD
6CL6
SUB-
CARRIER
MOD
SUBCARRIER
GENERATOR
30-67KC
L
'
I
I
AFC
I
I
FREQ.
CONTROL
---
VOLTAGE
I
I
I
6AU6
REFERENCE
CRYSTAL
OSC
6AH6
DIVIDER
(1/5)
lcARRIER
I
ON-OFF
2D2I
OFF-
FREQ
DETECTO
2-1N34A
PHASE
DETECTOR
l2AT7
CATHODE
FOLLOWER
6AS6
MIXER
LNTROL
_ - -
6AH6
DIVIDER
(
I/
3)
6AH6
DIVIDER
(I
/4)
6AH6
DIVIDER
(i
/4)
6AH6
DIVIDER
(I/
5)
I
I
I
I
_L
7 I
I
I
I
I
I
I
I
_J
I
I
I
MULTIPLIER-PA
A
V I
I
I
L
_J
,--7
I POWER SUPPLY I
+
300
VDC
I
I
+6
.3
VDC
I
6 .3 VAC I
L _
_J
I
I
I
I
_J
Figure
E-2.
Block Diagram,
BTE-1
OB
FM
Exciter
with
very
low
harmonic
disto
rti
on. Each
tube
is
almost
a
pure
reactance,
and
loa
ding
of
the
oscillator
is
greatly
reduced,
providing
better
AFC
action.
Moreover,
the
pushpull
modulator
a
utomatically
balances
out
temperature
and
s
upply
-
volt
age changes.
Modulating
circuits
are
ver
y effectively
decoupled,
thus
minimizing
the
possibility
of
cross-talk
between
the
main
channel°
and
subchannel,
and
vice versa.
Automatic Frequency
Control
The
automatic
frequency
control
circuitry
of
the
BTE-10B Exciter
is
characterized
by a
long
record
of
dependable
operation.
A
phase
detector
is
used
to
develop
a
control
voltage
which establishes
and
maintains
a
phase
lock
between
a reference crystal
oscillator
and
the
derived
signal.
Thus
the
system
is
actually
an
automati
.c phase
control
system which

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TO
CONTROL
VOLTAGE
REACTANCE
MOD
GRID
CI04
I
1N34A
INPUT
CONTROLLED
FREQ
.
C188
REFERENCE
FREQ.
?JI
T
111
Cl89
-
1N34A
Cl98
Cl87
~
----
1
Rl68
Ll08
+
Rl69
Rl70
+
-
K IOI
CONTACTS
E-7
Figure E-3. Simplified Schematic,
BTE-1
OB
Phase
Detector
achieves a stability precisely
matching
that
of
the
crystal reference
sourcf.:.
To
confine
the
phase devia-
tions
of
the master oscillator signal
to
within
range
of
the phase detector,
and
in
order
not
to exceed the
possible speed
of
the
low
pass
network
in
the
AFC
circuit, the master oscillator frequency
and
swing
must be reduced.
This
is
accomplished in locked-
oscillator type dividers
with
an
overall division
of
240.
Thus
the
maximum
phase deviation
at
the
lowest audio frequency
(30
cps) is ±58 degrees
(at
± 100 kc deviation
of
the
final
frequency),
and
well
within
the limits
of
linearity
of
the phase detector.
The
limited pull-in
range
normally
associated with
precise frequency
control
is overcome by the use
of
an
off-frequency circuit which extends the pull-in
range
to
±400 kc
(at
the final
frequency),
and
simul-
taneously provides a
safeguard
against
uncontrolled
and
possible off-frequency
operation
.
Circuits
of
the
AFC
system are
diagrammed
in
Figure
2.
A small r-f
voltage
is fed
from
the
master
oscillator circuit to the divider chain where
it
is
divided by 240
to
a
range
of
20 to
25
kc.
It
should
be
noted
that,
at
the
same time, deviation
due
to
modulation
is reduced from a
maximum
of
± 5 kc
to
±20 cps.
From
the
dividers, this voltage
is
fed
through
a
cathode
follower
to
a phase detector em-
ploying
two
IN34A
diodes. A reference voltage
of
the
same frequency, fed
into
the
phase detector,
is
obtained
by
dividing
by five the frequency
of
the
reference crystal oscillator.
Operation
of
the
phase detector
is
illustrated in
the simplified
diagram
of
Figure
3,
and
by
the
vector
diagram
of
Figure
4. Assuming
that
the master oscil-
lator
is
exactly
on
frequency,
with
no correction bias
applied
to
its
grid
,
the
two
input
signals applied
to
Tl
10
and
Tl
11
therefpre
are
of
the same frequency
but
90 degrees
out
of
phase.
The
reference frequency
signal
is
applied
to
Tl
10,
and
the voltage developed
across the
top
half
of
the
secondary is represented
by vector BA
in
Figure
4
(a)
,
while
the voltage
across the
lower
half
is
represented by vector BC.

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E-8
These
two
voltages are
equal
in
magnitude
and
180
degrees
out
of
phase.
The
controlled
frequency
signal
is
a
pplied
to
Tl
11,
and
the
voltage
developed
across its secondary
is
represented
by
vector
BD.
which
is
90 degrees
out
of
phase
with
each
of
the
other
two.
The
voltage
impressed across each
1N34A
crystal rectifier
and
its associated
load
(R169
and
RI
70)
is
then
the
\'ector sum
of
the series vol
tag
es
E,
and
E, respectively. Since
the
magnitudes
of
E,
and
E, are equal,
the
d-c voltages across
RI
69
and
Rl
70 will be equal
and
of
the
polarity
shown.
Hence
,
the
voltage
as measured
from
the
top
of
R169 to
ground
will
be
zero.
If, however,
the
frequency
of
the
master oscillator
should
decrease,
the
relative
phase
of
the
two
input
signals
and
their
vector
relationships
will
change
as
shown
in
Figure
4
(b).
Since
the
magnitude
of
E,
is
now
greater
than
that
of
E,,
the
d-c
voltage
across
Rl69
will be
greater
than
that
across R170
and
a
net
positil'e
correction
voltage
appearing
at
the
top
of
R169 will
be
applied
to
the
reactance
tube
grid,
correcting
the
frequency.
Accordingly,
if
the
oscil-
lator
frequency
should
increase,
the
vector relation-
ships
change
as
shown
in
Figure
4
(c),
and
a
net
negatii-e
correcting
voltage
is
applied
to
the
reactance
tube
grid.
Thus
any
departure
from
the
90-degree
phase
relationship
between
the
two signals
is
in-
stantaneously
corrected by a
proper
error
voltage
.
High
frequency
components
of
the
input
signals
are
filtered
out
of
the
control
voltage
by
the
capacitors
C188
and
C189
and
the
choke
L108.
The
network
consisting
of
capacitors
(104, (187,
CI
98
and
resistor R168
extends
the
control
range
of
the
phase
detector
beyond
the
±90
degree
phase
difference
limit
that
would
otherwise
be
imposed,
by
feeding
a
small
amount
of
the
beat
frequency
back to
the
reactance
tube
grid.
This
beat
frequency
then
causes
the
master
oscillator frequency to
swing
in
both
directions
at
the
difference frequency rate.
The
amount
of
frequency
deviation
is
proportional
to
the
amplitude
of
the
signal
at
the
reactance
tube
grid;
and
in.
or
_
der
to
produce
sufficient
swing
with-
out
objectionable
audio
frequency feedback, capaci-
tor
C187
is
made
small
and
is
paralleled
by a
larger
capacitor
(198
which
is
switched
in
only
when
the
master
oscillator
is
"hunting."
The
switching
is
done
automatically
by
the
off-frequency
detector
described
in a
later
paragraph.
If
the
signal
at
the
reactance
tube
grid
is sinusoidal,
there
will be
no
d-c
component
and
the
mean
fre-
quency
of
the
master
oscillator
will
remain
un-
changed.
However,
the
beat
frequency
at
the
phase
detector
output,
when
it
is
not
locked in, is non-
symmetrical
and
has a d-c
component
of
the
proper
polarity
to
change
the
mean
frequency
of
the
master
oscillator
toward
its
correct
frequency.
To
illustrate
how
the
non-symmetrical
waveform
is
developed,
take
an
example
in
which
the
frequency
of
the
master
oscillator
is
such as to
produce
a signal
at
T
111
which
is
0.1 kc low. A difference frequency
of
0.1 kc will be
fed
to
the
reactance
tube
grid,
and
El
----~
A
----,1:EI
A -I I A
I
I
........
/ I I I
........
'
/ I
I
I
):
El
/ I
I I D
/I
/ I
I
/ I
B
D
B
I
_,,/
I
I B
I
' "
I
' ' I \ I
' '
,1
\
D
' I
......
~
E2
\
,1
-\
----~E2
-\ I
C C C
',\I
(a) (b)
(c)
......_~E2
Figure
E-4.
Phase
Detector
Signal Voltages

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the
master
oscillator
will
then
swing
above
and
below
the
tuned
frequency
one
hundred
times
per
second.
The
dashed
line curve
of
Figure
5
(a)
is
the
waveform
of
the
beat
frequency
which
would
appear
at
the
junction
of
L108
and
RI
68
if
C104 were
shorted.
If
this
waveform
was fed back to
the
reactance cube
through
a
blocking
capacitor,
the
solid
line
waveform
would
appear
at
the
same
point.
Note
chat
the
solid
line
waveform
is
slightly
distorted
so
that
its axis
no
longer
represents zero d-c voltage.
The
positive
peak
of
the
solid
line
waveform
in
Figure
5
(a)
is
produced
as
the
master
oscillator
frequency swings
further
away
from
its frequency,
and
the
negative peak
is
produced
as
it
approaches
its
correct
frequency. As
the
contro
lled frequency
approaches
the
reference frequency,
the
beat becomes
increasingly slower,
and
the
distorted
waveform
is
produced.
The
d-c
componen
t
produced
across
CI
04
is
of
such
polarity
as to
change
the
master
oscillator
frequency
toward
its
correct
frequency.
Figures 5
(b)
through
(
d)
are
the
same as (
a)
except
for
the
frequency
of
the
beat.
Note
chat as
the
beat frequency becomes lower, the
distortion
becomes
greater,
producing
a
corresponding
in-
creasing d-c
component.
The
waveforms
shown
can
be
produced
by
blocking
the
d-c
component
from
the reactance
tube
and
by
tuning
the
master
oscillator
for
the
desired
beat
frequency.
However,
when
the
d-c
component
is
fed to
the
reactance tube
grid,
the
beat
frequency
automatically
decreases
until
it
is
zero.
The
system
is
then
"locked
in'"
and
the d-c
voltage
maintains
that
condition.
~
'
I
:\
I \
\ I
\ l
100'\i
(0)
V;
\
' \
\
' I
\ l
50'\,
(b)
E-9
Off-Frequency Detector
Protection
against loss
of
control
by
the
automatic
frequency
control
system,
and
possible off-frequency
operation,
is
provided
by
the
off-frequency
detector
circuit
shown
in
Figure
6.
VI
15
is
a 6AS6
mixer
stage
which
is
fed from
the
last
divider
in each chain
as
shown
in
Figure
2.
The
plate
load
of
the stage
is
by-passed by capacitor
CI
93, which
is
a low im-
pedance
to
the
beating
frequencies
and
to
the
sum
of
the
beating
frequencies,
eliminating
these signals
in
the
output.
When
the
master oscillator
is
on
frequency there
is
no difference frequency
produced
in V115,
and
therefore
the
output
of
the
stage
is
zero.
If
for
any
reason a difference occurs in
the
two
beating
fre-
quencies, however,
the
difference frequency com-
ponent
appears
across
the
plate
load
and
hence across
the
thyratron
grid
resistor R 172.
If
the
positive
half
of
this
alternating
voltage
exceeds
the
fixed
cathode
bias
applied
to
the
thyratron
VI
16,
the
tube
con-
ducts,
energizing
relay
KIOI.
One
(normally
closed)
set
of
contacts on relay K
10
I
operates
the
trans-
mitter
interlock
circuit,
preventing
plate
power
from
being
applied
to the PA;
another
set
of
contacts
(
normally
open)
switches in
the
feedback capacitor
C198,
shown
in Figure
3,
for
purposes
previously
described.
Sensitivity
of
the circuit
is
adjusted
by
the
thyra-
tron
bias resistor
R
174.
This
adjustment
is
set so
that
the
low
modulating
frequencies will
not
trigger
the
thyratron
but
so
that
the
beat frequencies will
cause it to fire.
(c)
(d)
Figure E-5.
Phase
Detector Output Waveforms

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E-10
V115
V116
0:
=
KIOI~
UJ:,,:
C 193
---s£l!
I- u
t: 0
CONTROLLED
::E .J
FREQ . (/)
0:
zW
<I'. I-
0: ~
I-
REF
FREQ
-
Tll2
B+
TO
FIL TRANSF.
Figure E-6. Simplified Schematic, Off-Frequency Detector
INSTALLATION
Carefully unpack and inspect the equipment to
make certain that no damage has been incurred dur-
ing shipment. Any damages or shortages should be
immediately reported to RCA and to the transporta-
tion company in order that lost or damaged material
may be recovered.
The equipment is shipped complete in one con-
tainer,
excepting tubes and crystals which are packed
separately.
All internal wiring is done at the factory,
only external cables and wiring need be prepared
and connected to the equipment at installation.
Reference should be made to the interconnection dia-
gram of this book which designates the cables and
wiring to be used and the proper connections.
A-C Power Line Connections
The primaries of the plate transformer (TI 13) and
the filament transformer (TI 14) are each tapped for
operation from either 120-volt or 240-volt single-
phase a-c lines.
The equipment is shipped with the
taps set for 240-volt use. The crystal heaters 11111st b1:
rnllllffled 011ly to a 120-t·olt a-c source. Particular
care must be taken to insure that proper connections
are made before power is applied to the equipment.
Reference should be made co the overall schematic
diagram and to the table Tramfor111er Primary Tap.1
for making connections. // 2-10 /'()Ifs is wed, b1: S1tr1:
110/ to disw1111ect T ll 2 ( black leads) f ro111 th 1: 120-
l'Olt ten11i11al s -I (IIJl/ 2 of T 113.
The a-c overload switch (S104) can be used as a
"Power Off-On" switch, if desired, and the d-c u, ·er-
luad switch (S103) for "Standby" plate switching.
The connections of these circuit-breakers are shown
in the overall schematic diagram.
Tubes should be inserted in their proper sockets
by
reference to the type number designations printed
near the appropriate sockets. Crystal Units MI-34509
should be inserted into the sockets marked ''CRYS-
TAL I" and "CRYSTAL 2."
TRANSFORMER PRIMARY TAPS
Power Line Voltage:
106 117 128 197
208
I 219 229
240 251
Taps to be Used:
3-4
2-4 1-4
3- 5 2- 5 I 1
-5
3--6
2-6
1-6
---------------
Tap C of
Tap B of
"AC OVERLOAD" "AC OVERLOAD"
Circuit Breaker
Circuit Breaker

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After
tubes
and
crystals
are
in place,
and
all con-
nections are
properly
made, a-c
power
can be
applied
to
the
equipment.
Allow
sufficient time
for
tubes
and
the
crystals heaters to reach
operating
temperature
before
following
the
tune-up
procedure
below.
Indicators
DSl0l
and
DS102
will
light
when
the
crystal oven heaters
are
on.
Tune-Up Procedure
The
oscilloscope
patterns
illustrated
m these pages
were
obtained
on
the
built-in
CRO
during
tune-up
of
an exciter unit.
These
patterns
should
be con-
sidered as typical
of
those to be expected;
slight
de,
·iations
from
these displays may occur in indi-
vidual units.
I.
\X
1
ith
the
equipment
operating
and
indicators
"DS
101
··
and
"DS
102"
extinguished,
indicating
that
the crystal heaters have reached
operating
tempera-
ture
, switch
"AFC-OFF"
· switch to
"OFF"
position
.
With
the
CRO
Switch
(Sl06)
in
any
position,
ad-
,·ance
the
"
INTENSITY"
control
(R
185) clockwise
until a trace
appears
on
the
face
of
the
tube
(VI
18).
Then
adjust
"FOCUS"
(R
183)
for
proper
sharpness
.
Switch meter-switch
(S102)
to
"Vl07
E
,.
" posirion
and
check
plate
voltage.
(Reading
should
be between
54
and
66.)
Turn
"OFF-FREQUENCY
INTER
-
LOCK
SENSITIVITY"
(R 1
76)
to
extreme
clock-
wise position.
2.
Turn
CRO
switch to
"XT
AL
DIV"
position.
Adjust
top
screw
of
LI I2
for
maximum
horizontal
size
of
CRT
pattern.
( I
/8"
to 3/ I
6"
will be satis-
factory)
.
3.
Adjust
top
screw
of
Tl
15
to
obtain
stationary
Lissajous' figure
indicating
a division
ratio
of
I
/5.
(
Pattern
should
have
five
left-hand
loops
and
five
right-hand
loops.)
Adjust
top
screw
of
Tl09
for
maximum
vertical size
of
pattern.
See
Figure
7
a.
4.
Set
the
master
oscillator
to
the
approximate
operating
frequency
which
is
1/
18
of
the
final
carrier
frequency. E.g., 88.1
me
corresponds
to 4894 kc
master
oscillator
frequency.
Use
grid-dipper,
cali-
brated
receiver
or
frequency meter. Use
bottom
screw
of
TI03
to
make
this
adjustment
setting
the
top
(fine)
adjustment
to a mid-position.
5.
Turn
CRO-Switch to
"lST
DIV"
position
and
adjust
T14
for
a
stationary
Lissajous' figure
and
a
division
ratio
of
1
/3.
See
Figure
7 b.
NOTE
:
Too
high
an
inductance,
when
che adjusc-
ing
screw
is all che
way
in,
means
a
low
frequency
and
a
possible
division
racio
of
I/
4
or
I
/5
or
more.
Too
low
an
indunance
may resulc in a
1/2
division
racio.
6.
Turn
CRO-Switch to
"2ND
DIV"
position
and
adjust
T105
for
a
stationary
Lissajous' figure
anq
a
division
ratio
of
1
/4
(Figure
7
c).
E-11
7.
Turn
CRO-Switch to
"3RD
DIV"
position
and
adjust
T!06
for
a
stationary
Lissajous' figure
and
a
division
ratio
of
1/4
(Figure
7
d)
.
8.
Turn
CRO-Switch
to
"4TH
DIV"
position
and
adjust
TI
07 for
stationary
Lissajous' figure
and
a
division
ratio
of
1/5
.
Adjust
TI08
for
maximum
hori-
zontal
size
of
pattern
(
figure
7
e)
.
9.
Turn
CRO-Switch to
"PHASE
DET
" position.
A
square
of
medium
brightness
should
be seen repre-
senting
an unstacionary Lissajous' circle.
The
rate
of
change
of
the
circle
depends
on
the
frequency-differ-
ence between the reference sighal
and
the
divided
master
oscillator
signal.
Rotate
the
bottom
screw
of
Tl03
slowly in
both
directions
trying
to find
the
point
where
both
signals
agree
in frequency
resulting
in a slowly
changing
Lissajous' circle.
During
the
variation
of
TI
03
make
sure
as you
change
frequency
that
all dividers
(T104
-
TI07)
are still locked in.
If
a
nearly
stationary
circle
cannot
be
obtained,
try
again
starting
on
a
somewhat
higher
or
lower fre-
quency.
10.
If a slowly
changing
circle was
obtained.
s,,itch
meter
switch
(SI02)
to '
'VIOi
&
Vl02
I
i-"
position
and
adjust
"l\lODULA
TOR
GRID
TUN
-
ING"
(C105) for
peak
indication
.
Slight
resetting
of
Tl03
bottom
adjustment
may be
required
to
obtain
slowly
moving
Lissajous' circle.
Then
switch
"AFC"
switch (S
IO
1)
to
"ON
" position.
The
circle
should
"jump"
into
a
completely
stationary
circle now. (See
Figure
7
f.)
In
addition
to
the
CRO
the
phase de-
tector
output
vo
lt
age
can be observed also on the
built-in
meter,
with
the
meter
switch in "
or
-
AFC"
position.
With
AFC
on,
both
positions
should
give nearly zero readings.
With
AFC
off,
frequency differences
at
the
phase
detector
up
to a
few cps can be observed
with
the
meter.
11.
A
more
sensitive
adjustment
of
"MODU-
LATOR
GRID
TUNING"
(CI05)
can be
made
by
applying
50 cps
at
approximately
t- 10
db
to the
audio
input
connector
(J
101
),
and
adjusting
C105
for
maximum
indication
on
the
modulation
per-
centage
meter
of
a
modulation
monitor.
12.
Tune
L104 to
maximum
indication
of
the
meter
(MlOI)
with
meter
switch
(S102)
tn
"I
,
VI
06"
position.
13.
Steps
11
and
12
may
slightly
change
the
master
oscillator
frequency. So,
AFC
shou
ld be switched
off
and
with
CRO
switch in
"PHASE
DET"
position
the
circle
should
be
made
near-stationary by
tuning
TI
03
with
the
fine
control
knob
on
top
of
the
can.
Then
throw
"AFC-OFF"
switch back
to
"AFC"
position.

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E-12
.(a J Switch Position:
"XT AL DIV." f1 /SJ (b J
Switch Position:
"1st DIV." f1 /3 J fcJ
Switch Position:
"2nd DIV." f1/4J
(d J Switch Position:
"3rd DIV." f1/4J
(e J Switch Position:
"4th DIV." f1 /SJ
(fJ Switch Position:
"PHASE DET."
Figure E-7. BTE-108 Oscilloscope Patterns
NOTE: Tl04 to TI07 stay locked in over a certain
frequency range. It is desirable to have TI04-TI07
adjusted so that they normally operate in the middle
of their lock-in range . In order to assure this,
switch CRO-Switch to "1ST DIV" position. Now
turn tuning screw on top of TI04 to the left until
the divider unlocks (Lissajous' figure gets " fuzzy") .
Start turning screw to the right and observe the
number of revolutions until it unlocks at the other
end of the range. Turn screw back half the number
of revolutions counted. Repeat this for TI05, Tl06,
TI07, and TIIS .
14. Tune L105 to maximum indication of meter;
meter switch in "l e V107" position.
NOTE: Remove C214 for center frequencies above
100 me.
15. Tune Cl37 "PLATE TUNING" to dip on
meter, meter switch in "Ik V107" or better in "II'
Vl07" position. Adjust Cl39 "OUTPUT TUNING"
to obtain proper grid current in following amplifier
or desired output, then retune C 13 7 for dip or maxi-
mum output . (If a Micromatch or Reflectometer is
used in the output transmission line, the developed
DC voltage may be fed into the exciter via pin 8.
of plug Tl05 and indicated on the meter, meter switch
in
"POWER OUTPUT" position.)
16. Adjust the sensitvity of the off-frequencr
detector (V 116) as described in ,he following para-
graphs.
NOTE CAREFULLY: This adjustment is important
to assure sufficient pull-in range of the exciter.
Then proceed with Steps 17, 18, 19 and 20.

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"OFF-FREQUENCY INTERLOCK" Adjustment
Sensitivity
of
the
off-frequency
detector
(VI
16)
1s
controlled
by
the
setting
of
the
"OFF-
FREQUENCY
INTERLOCK
SENSITIVITY"
potentiometer
(RI
74)
in
the
cathode
circuit
of
this stage.
Proper
adjust-
ment
can be
obtained
by use
of
either
a
35
cps
or
50 cps
tone
source,
although
the
methods
differ
slightly
as
follows:
Using
a 35-cycle tone,
modulate
the
exciter I
30%.
An
input
signal
of
approximately
n
db
is
re-
quired.
Turn
R174 counter-clockwise
until
relay KIO 1
is
energized, as observed by
listening
for
the
closing
of
the
relay
or
bf
operation
of
the
PA
plate
or
screen
cutout.
The
point
at
which relay K
10
I
1s
energized
will be
the
correct
setting
for
R174.
If
a
35
cps source
is
not
available, an
alternate
method
using a 50-cycle
tone
source may be used.
Modulate
the
exciter l 3G%
with
the
50-cycle tone,
and
turn
R174 counter-clockwise to
the
point
where
K10I
is
energized.
Note
this setting.
Then
turn
R174
clockwise
until
K
101
is
de-energized,
noting
this
setting.
Then
set R174
halfway
between these ener-
gized
and
de-energized positions, which will be the
E-13
correct
adjustment.
Check
for
proper
off
-frequen
cy
control
action by
switching
the
"AFC
SWITCH"
(Sl0l}
to
"OFF"
and
slightly
detuning
the
vernier
control
on
the
top
of
Tl03.
This
should
energize
relay K 101.
Retune
TI
03 to
original
setting.
17.
Set
CRO-Switch
(S106} to
"PHASE
DET"
po
sition
and
reduce
"INTENSITY"
(Rl85)
to pre-
vent
burn-in
of
the
pattern
.
18.
Fina.II)',
using
the
station
frequency
monitor
tune
the
crystal
"FREQUENCY
ADJUSTMENT"
trimmer
capacitors (
(205)
and
(
(206)
to
the
as-
signed
center
frequency.
((205
or
(206
will vary
final frequency
approximately
±
15
kc.)
NOTE:
Frequency
rnn
be
changed
slightly
by
adjustment
of
LI
12
also.
Do
noc
change
more
,han
± 2 kc.
19
.
Reduce
"INTENSITY"
(Rl85)
as much as
possible to
prevent
CRT
"burn-in".
20.
Multiplex
Operation.
Best crosstalk will be
obtained
with
all
multiplier
and
amplifier
stages
tuned
for
maximum
grid
current
in
the
following
stage
or
for
maximum
power.
OPERATION
In
daily
operation
of
the
equipment,
the crystal
heaters should be
left
on
continuously.
Then
after
application
of
power
to
the
exciter,
and
allowing
a
short
warm-up
period,
performance
can be checked
by
observing
the
patterns
on
the
oscilloscope
while
the exciter
is
on
the
air.
The
oscillograms
shown
with
the
tuning
procedure
in
the
INSTALLATION
section
of
this book repre-
sent
the
desired
adjustment
of
the
various stages
of
the
exciter
for
proper
operation
of
the
AFC
system.
These
oscilloscope
patterns
may be observed
during
regular
operation
without
affecting
performance
of
the
exciter.
The
75
1,s
pre-emphasis
network
is
a
plug-in
unit
and
can be
removed
if
it
is
desired to
apply
pre
-
emphasis at
some
other
point
in
the
system.
If
this
unit
is
removed, an 18
db
pad
should
be
inserted
in place
of
the
pre-emphasis
network.
Such an attenu-
ator
can be
made
up
in accordance
with
Figure
8.
Numbers
on
the
diagram
identify
the
octal
pins
of
the
socket
XZ
IO
I.
The
use
of
±
5";~ tolerance,
½
watt
resistors
is
recommended
.
Output Frequency Conversion
A conversion coil
(Ml-34501-2)
1s
supplied
with
the
exciter
to
modify
the
last
stage
to
a
straig
ht
-
through
amplifier,
providing
an
output
frequency
in
the
range
of
44 to 54 mes.
If
the
exciter
is
to be
used
with
previously
designed
FM
transmitters
in-
corporating
a frequency
doubler,
this modification
sh
ould
be
made
in
the
exciter.
If
it
is
necessary
that
the
exciter
operate
on
one-
half
of
the
final frequency, modification
of
the
output
stage
should
be
made
in
accordance
with
the
foliow-
ing
procedure
using
the
conversion coil.
I.
Remove
all
power
from
the
exciter unit. Remove
the
cover
enclosing
components
of
the
final stage,
and
remove
the
6146
tube
(V107}
.
470
470
3 4
150
5
6
Figure E-8. Schematic,
18
db
Attenuator

www.SteamPoweredRadio.Com
E-14
2.
Unsolder
the
r-f
choke
(L107)
from
the
feed-
through
capacitor
(Cl46),
and
remove
units
that
hold
the
plate
component
mounting
bracket
in
place.
The
bracket
can
then
be
turned
to
gain
access to screws
holding
the
plate
coil
(L106).
Remove
this coil,
and
install
the
new
coil
(Ml-34501,
Item
2)
in
its place.
3.
Put
mounting
bracket
back in place,
making
sure all
mounting
screws
are
tight.
Re-solder L107
and
C146
in
such a way
that
there
will be
at
least
½-inc
h clearance
between
L107
and
the
cover
when
the
cover
is
in position.
4. Reinsert tube V107 in its socket,
and
install the
cover
in
place.
This
completes
the
modification. Fila-
ment
and
plate
power
can
now
be
applied.
With
the
modification made,
power
output
will be
between
10
and
15
watts.
NOTE
:
In
an
emergency,
the
RCA 6146
(YI07)
may be
replaced
by an RCA 2E26,
at
somew
hat
redu
ced
power
ou
tput,
should
the
latte
r
tube
be
more
readily
availab
le
.
No
change
in conn
ections
is
required.
Main
Carrier Deviation
by
the
Subcarrier
Approximate
deviation
of
the
main
carrier
can
be set
without
a
monitor,
using
only
a
subcarrier
generator
and
the
chart
shown
in
Figure
9.
The
chart
indicates
the
amount
of
subcarrier
voltage
necessary
'°
0
.,
ii
0
at
the
input
of
the
BTE-lOB Exciter (J-102
or
J-106)
to
produce
the
required
deviation.
As
indicated
on
the
chart,
the
higher
subcarrier
frequencies
require
slightly
more
voitage
than
the
lower
frequencies.
To
obtain
a
±
10 kc
deviation
of
the
main
carrier
at
67 kc, 3.6 volts
should
be
selected.
At
a 32.5 kc, 2.6 volts will
produce
the
same
main
channel
deviation.
The
above
method
is
approximate
and
subject to
tolerances
in
the
order
of
±
25
percent.
It
is recom-
mended
that
the
reactance
tube
V-104 be
compared
with
2
or
3
other
6CL6 tubes.
One
method
of
doing
so
is
by
measuring
relative
subcarrier
voltage. A
multiplex
receiver
(with
main
program
off)
should
produce
a
voltage
of
0.1 to 0.2 volts
at
the
discrimi-
nator
with
±
15
kc
deviation
of
the
main
by
the
subcarrier.
Using
several 6CL6 tubes this
voltage
should
remain
the
same.
Proper
setting
of
L-104
in
the
BTE-
JOB
(maxi-
mum
grid
current
into
the
2nd
tripler)
will coincide
with
minimum
subcarrier
-cteviation
of
the
main
channel.
Detuning
of
L-104 will increase crosstalk
as well as
subcarrier
deviation
of
the
main
carrier.
Therefore,
L-104
should
be
set
to
maximum
grid
current
into
the
following
tripler
stage
for
minimum
crosstalk.
n,
8
67KC
32.5KC
0
t----t----t-----11-----+---+----,.---t----+--------11------t
.,
I-
C
laJ
"
<
I-
..,
0
>
IIC
I&,(
6
a::
2
a::
~
ID
:)
.,,
0 4 a
12
.,
20
24
28
ICC
DEVIATION
(MAIN
CARRIER
BY
SUBCARRIER)
8520017
This
chart
indicates
the
amount
of
subcarrier
voltage
necessar
y
at
the
input
of
the
BTE-10B
Exciter
to
produce
a specific
frequency
deviation.
Figure E-9. Main
Carrier
Deviation
by
the
Subcarrier
(Chartl

www.SteamPoweredRadio.Com
UG 57 8/U
ADAPTOR
39OOil
TO PIN 8 P1O5
TO PIN 7 PIO5
E-15
JIO3 M.
C. JONES
TYPE 573N4
Fig ure E-10. Connections for Measuring Power Output
Subcarrier Modulation
To increase subcarrier modulation percentage , a
47K ohm, ½ watt resistor should be connected in
parallel to Rl95 or Rl97.
Use of Control Tones
The exciter can be modulated by control tones if
desired.
These control tones, which are generally in
the
rang e between 20 kc and 35 kc, should be fed
into one of the subca rrier input jacks ()106) on the
exciter. With approximately 5 volts as measured at
this
point , 30% modulation of the main carrier will
be
obt ained.
MAINTENANCE
With normal care, no maintenance should be
required except a periodic check of all tubes and
replacement of defective ones with new tubes of the
same type.
Failure of automatic frequency control due to the
failure of a tube or other component will be ev i-
denced by operation of the relay K10 I in the off-
frequency
detector circuit, opening the contacts
(Terminals No. 5 and No. 6 of )105) that control
the PA stage of the transmitter. If failure is due to
a defective tube,
proper operation of the exciter
will be
restored by replacement of the defective tube
without need for readjustment. However, if replace-
ment of circuit components is made, it will be neces-
sary to
realign the exciter following the procedure
for tuning presented under INST ALLA TI ON .
Emergency Operation
Provision is made for maintaining frequency con-
trol
should tupes or components associated with the
automatic frequency control fail. The operator will
be
warned of the loss of control by loss of carrier,
or by the erratic performance of the carrier frequency
monitor.
Tube or component failure can be found in some
cases by
switching the meter switch (S102) through
each of its positions until an abnormal reading is
found identifying the difficulty. The oscilloscope
switch
{S106) may also be helpful in locating trouble
in the AFC circuits.
If the master os cillator is functioning , the output
carrier frequency can be controlled manually as fol-
lows, until such time as repairs can be
made :
I. Remove the 202 I " OFF-FREQ U ENCY' . con-
trol tube
(V116).
2. Turn the "AFC.OFF" switch (SI0I) to " OFF ".
3. Slowly rotate the top a djustment screw of Tl03
in first one direction and then the other to bring the
output frequ ency to its assigned value as indicated
by
the frequency monitor.
Stability of the master oscillator without AFC is
such that after sufficient warm-up it maintains fre-
quency to ± I kc (
at the final frequency) for short
periods of time . Possible drift can be corrected by
adjustment of Tl03 top screw.
CAUTION: The voltag e of the filament
d-c
power supply will 1·ary with load. There-
fore, care
should be take11 11ot to remo1•e
more tha11 two of the tubes having d-c 011
the fila111e11t. Otherwise, damage to tbe
remaining d-c bn1ted tubes or to C202 may
result.
Power Output Measurements
Power output indications can be obtained con-
veniently by use
of the meter (M 101) and a suitable
coupler such as the M. C. Jones Micromatch. With
the meter switch (SI02) in the "POWER OUTPUT "
position,
the positive terminal of the meter is con-
nected to Pin
No. 7 (ground) of PI05 and the nega-
tive
terminal to Pin No . 8 of P105. Readings obtained

www.SteamPoweredRadio.Com
E-16
will
depend
upon
the
type
of
coupler
used. \Y/ith an
M.
C.
Jones
Type
573N4
and
a
UG57B/U
adaptor,
a
3900-ohm resistor in series
with
the
meter
will pro-
vide mid-scale
reading
of
the
meter
at
ten watts
output.
Connections
should
be
made
as
shown
in
Figure
10.
The
parasitic
suppressor
Rl
38-
Ll
13
is
nor
required
whenever
tube
V107
is
operated
as a
doubler.
In
an
application
where
maximum
possible
output
power
is
desired,
R138-L113
may be removed.
Additional
power
may be
obtained
by
shorting
out
Rl32.
Under
such
conditions,
however,
V107
should
not
be
operated
without
r-f
excitation. Lack
of
excita-
tion
will increase
the
plate
current
of
V107 to a
point
where
S103 will be energized.
To
make
tuning
more
practical, a switch
should
be placed across
RI
32.
This
switch will be closed
only
after
sufficient
drive
has been
obtained,
as
indicated by
MIO!
in
the
Vl07
I
position
.
TYPICAL
METER READlNGS
Meter
(MlOl)
Reading
Position
Function
88
me
108
me
VlOI
&
VI02
I.
Modulators
63 64
VI06
I, 2d Freq.
Tripler
39
35
VI07
I,
Doubler
&
PA
41
35
VI07
I.
Doubler
&
P.A
68
66
+AFC
Control
Voltage
<10 <10
-AFC
Control
Voltage
<10 <10
Vl07
E
0
Doubler
&
PA 62 62
Vl07
I•
Doubler
&
PA
49 48
POWER
OUTPUT
PA
(see
text)
I
TYPICAL
TUBE
SOCKET VOLTAGES*
BTE-1
OB
FM Exciter
Tube
Symbol
Type
1
2
3
4
VIOi
6AQ5
.2
15.5 0 6.4
v102
6AQ5
O'
15.5 0 6.4
V103 6AQ5
-17
0 0 6.4
VI04
6CL6 7.6 0 150 0
Vl05
5763 320 -
10
0
Vl06
5763 320
-
10 0
V107 6146 48 6.3AC 225 48
v1os
6AH6
-4.5
75
0 6.3AC
VI09
6AH6
-s
90
0 6.3AC
Vll0
6AH6
-13
95 0 6.3AC
Vlll
6AH6
-7
100 0 6.4
V112
6AU6
-9,5
0 0 6.3AC
V113
6AH6
-7
88 0 6.4
Vl14
12AT7 240
.5
4.3 0
Vl15
6AS6 0 2.2 0 6.3AC
0 2.7' 6.3AC
V116
2D21 1.5AC' 0
V117
OD3
-•
2.4 -150
V118
lEPl
0 6.3AC 2.5
1
9
• Voltages measured
with
VTVM
against
ground;
values
are
positive except
where
marked otherwise.
·
'May
vary ±
IV
due
to AFC. If more than +
IV
or
-
IV,
correct setting of
Tl
03.
'Measure
at
junction of
Rl26
and
Rl27.
'Measure
at
junction of R130
and
Rl31.
p j n
N
0
5 6 7
8 9
10
11
150 150 .2 -
- - -
150 150 O'
- - -
-
150 70
-17
- - - -
6.4 150 7.6 150 0
- -
6.0 270
10
-25
--25
-
-
5.9AC 270
10
-2.2
2
-2.2'
-
-
-2.s'
75
90
95
100
145
88
0
120
2.7'
150
so•
48 0 0 -
- -
75
0
-- -
-
90 0 -
- -
-
95 0 -- - -
100 0
-
-
-
-
70 0 -
- -
-
-7
0
---
-
240
-1
4.2
6.4 - -
85
0 -
--
-
145AC'
2.7'
--- -
-100
-
-- - - -
-•
320 320
-·
320
-
'Figures
above
line:
relay de-energized; below line: relay
energized.
'Depends
on
setting
of
RI
74, Typical
value
shown.
'
Do
not
take reading.
'Depends
on
setting
of R185. Typical value shown.
'Depends on
setting
of R183. Typical value shown.
'Reading difficult,
due
to
large
value of
Rl87
and
RISS.

www.SteamPoweredRadio.Com
E-17
TROUBLE
SHOOTING HINTS
RECOMMENDED TROUBLE SHOOTING
EQUIPMENT
Equipment
Type
Vacuum
Tube
Voltmeter
RCA
Voltohmyst
WV-98A
with
with
RF
Probe
WG-301A
Probe
or
Heath
V-7A
with
Probe
#
309C
or
Equivalent
Audio
Oscillacor
Hewlett-Packard
206A
or
Heath
AG
-9A
or
Equivalent
Oscilloscope
RCA
W0
-88A
with
WG-300A
Probe
or
Heath
0-
12
with
Probe
PK- I
or
Equivalent
Receiver
National
NC-109
or
Equivalent
Grid
Dip
Meter
Me
a
surements
Corp.
#
56
Heath
GD-18
The
BTE-10B Exciter consists
of
the sub-units listed
below;
trouble
shooting
the exciter
should
follow in
the
order
as
given below.
(!)
Power Supply
(V!l7)
(2)
RF
Portion
(Tubes
VIOi
to
Vl07)
(3)
Oscilloscope
(VI
18)
(4)
AFC
(Tubes
VI08
to
VI
14)
(
5)
Off Frequency
Control
(Tubes
VI
15
and
VI
I
6)
1.
Power Supply
\X'ith
SI
04 closed, check voltage
at
pin 5
of
XC202.
This
voltage
should
be 6.3 volts
DC
±
5%,
and
posi-
tiv~ with relation
to
ground
.
The
AC volcage at pins
IO
and
11
of
Tll4
should
be 6.3 volts, and between pins 7
and
9,
22
volts.
With
S103 closed, check voltage
at
pin
5
of
Vl
17.
It
should
read
+
150 volts.
To
check
current
through
Vll7,
measure the
DC
voltage across
Rl94
.
Multiply
this
reading
by
10
to
get
the
current
through
the
tube.
This
current
should
be between
15
and
25
ma.
The
voltage across R194
should
be 1.5
to
2.5 V DC.
The
voltage across C200 can be read
on
MIOl
with
switch S102 in the
Vl07
E,,
position.
Multiply
the
reading
on
MIO1
py
5 to
get
the actual voltage.
The
AC voltage at pins 7
and
8
of
Tl
13
should
be 370
volts.
Sl03
will
trip
at
approximately
400 ma
through
control
winding
(C
to
D).
If
proper
voltages are available from the
power
supplies, proceed
to
the next section.
2.
R-F
Section
Switch SIOl
to
AFC-OFF
position.
Check pin voltages
of
VI03
as given in
table
of
Typical
Tube
Socket Voltages
for
BTE-10B
FM
Exciter.
The
voltage
on
pin 1 should be measured
using a I megohm isolation resistor (this resistor is
part
of
the
DC
probe
of
the
VTVM
recommended in
the
Trouble
Shooting
Equipment
Chart).
If
the volt-
age across
RI
16
is
very small the tube is
not
oscillating
and
another
rube
should
be tried.
Next,
measure the r-f voltage across pins A and D
of
coil
Tl03
. Approximately 2 V rms
should
be pres-
ent
. Use
VTVM
with RF-probe.
Tune
Cl05
for
a
peak
reading
on
MIOI
with the selector switch in
the
VIOi
and
V102 11
, position.
When
peaked, 7 V
rms
(r-f
voltage) should be present
on
pins 1
and
7
of
VIOi
and
of
VI02.
The
r-f voltage
on
pin 5
of
VIOi,
Vl02,
and
V103
is
l00
volts.
On
terminal E
of
T103
the
volta8e
is
35 volts. These voltages
cannot
be measured with
the recommended
VTVM
since there
is
a limitation
of
20 V rms
for
the r-f probe.
Check
pin
voltages
of
V104.
There
is
no
adjustment
that
will effect these voltages.
Check
pin
voltages
of
VI05.
If there
is
no voltage
on
pin 8
and
9, try a new tube
and
check
Cl2
l.
Tune
L104
for
maximum
grid
current
into
VI06.
If
no
grid
current
can be obtained, try a new V106
or
check
whether
LI04
and
Cl25
resonate
at
3 times
the oscillator frequency. Use
grid
dip meter (exciter
plate voltage off
and
dip meter in
CW
position)
or
use
the
receiver tuned
to
3 times the oscillator
frequency,
and
couple the
antenna
input
loosely
to
pin
1
of
V105. Set IF gain
of
the receiver such
that
the
S2
reading
is
obtained
on
the
S-Meter.
Try
to
increase this indication by
tuning
L104.
Proceed in the same way
with
the second tripler
Vl06
. .
For
frequencies above 100 me, C214 should
be removed.
To
check the PA, a
10
watt
dummy
load
should
be made
up
using 5 resistors (composition type)
of
270
ohm,
2
watts in parallel.
At
10 watts
output
the r-f voltage across this
54
ohm
load
should
be 23 volts rms.
Refer
to
Off-Frequency
Detector
section
for
test
with
modulation
on
.
3. Oscilloscope
It
should
be possible
to
get
some trace
on
the face
of
V118 irrespective
of
the
setting
of
S106. Check
VI
18
pin voltages
if
necessary,
and
make sure that
the tube
is
properly
inserted in the tube socket.
Adjust
Rl85
and
Rl83
.
If
it
is
not
possible
to
reduce
the intensity
to
zero with
Rl85,
a 1.5 megohm I watt
resistor should be connected
from
pin 4
to
pin 8
of
Vll8.

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E-18
4.
AFC
Check
the
pin
voltages
of
tube
Vl
12. In
order
co
oscillate,
Ll
12
and
the
associated capacitors (
Cl
76,
C204,
and
C203)
should
resonate
at
a
frequenc
y
approximately
50%
higher
than
the
cryst:1.I
used.
(See table
for
BTE-10B Exciter Crystals.)
When
Vl
12
is
properly
oscillating,
the
following
r-f voltages
(measure
with
VTVM
and
r-f
probe)
should
be
measured :
3.
5 volts rms
at
terminal
B
of
L112;
6.
5
volts rms
at
pin
5
of
V112,
and
1.
5 vol ts rms
at
pin
1
of
VI
12
.
The
above
voltages
are
nearly
sinusoidal in char-
acter.
Once
Vl
12
oscillates
properly,
the
crystal
divider
can be locked in.
This
will
produce
a steady
pattern
on
the
oscilloscope
with
Sl06
in
the
CRYS-
TAL
DIV
position
.
The
following
waveforms
and
voltages can · be
observed:
Pin
1
of
V113
should
be
17
volts
peak
-
co-
peak,
somewhat
resembling
a ner;ative
half
wave;
and
a 140
volt
peak-to-peak
distorted
sinewave
ac
pin
5
of
Vl
13.
At
terminal
A
of
TI09
a 27
volt
rms sine-
wave can
be
measured.
The
VTVM
in
the
AC
posi-
tion
should
be used since
the
frequency
ac
T 109
is
between 20 a
nd
25
kc.
The
voltage
ac
terminal
D
of
Tl09
is
7 volts rms.
This
signal can be
followed
co
terminal 1
of
T 110
where
5 volts rms
should
be
read
.
The
same
procedure
should
be
followed
for
the
other
divider
chain, V 108
through
V111.
The
wave-
form
appearing
at
the
pla
ce
of
all cubes will be sym-
metrical
and
look
like a
distorted
sinewave. All
grid
waveforms
are
clipped
sinewaves
with
only
the
nega-
tive
portion
remaining
.
The
clipping
and
distortion
is
less
pronounced
in
the
first
and
second dividers.
The
peak-to-peak AC voltages
ac
the
grids
of
the
first, second, etc.,
divider
s
are:
5.0,
14
, 28 a
nd
24
volts respectively.
The
plate
AC
peak
-
co
-
peak
voltages
of
the
dividers
are 50, 140, 220 a
nd
160 volts
respectively.
At
terminal
D
of
Tl08,
14
volts peak-co-peak
should
be
measured
;
at
terminal
1
of
T
111
the
rms
voltage
should
be
3 volts.
With
the
master
oscillator
right
on
frequency,
the
DC
voltage
at
the
junction
of
L108
and
R168
should
be
very close to zero
with
the
AFC
switch in
the
ON
position.
With
AFC
off,
and
SI06
in
the
PHASE
DET.
Position
, a slowly
turning
circle will be ob-
tained
at
the
CRT.
In
synchronism
with
the
slowly
turning
circle a very low-frequency
AC
voltage
should
appear
across
the
phase
detector
output.
This
voltage
can
be
observed
at
M 101
with
S102 in
the
plus
or
minus
AFC
position. If
the
final frequency
(the
assigned frequency
of
the
station)
is
off
center
by
4320
cps,
Meter
MlOl
will
swing
from
maximum
positive to
maximum
negative
and
return
to maxi-
mum
positive
indication
in I second.
The
meter
should
show
a m:ixi
mum
reading
of
±
80%
on
ics
dial, re
presenting
± 8 volts
at
the
junction
of
L108
and
Rl68.
If
less
than
± 8 volts
is
obtained,
c.:heck
the
AC voltages
into
T 110
and
TI
11,
and
if
these
voltages
are
correct, check diodes
CRlOI
and
CR102.
With
the
AFC
ON,
ic
should
be possible to
detune
Tl03
(rear
adjustment)
up to a
point
where
MlOI
reads steadily ±
80%
in
the
±
AFC
position
without
loss
of
AFC
action.
If
control
is
lost
before
reading
a ±
80%
indica-
tion check,
(without
retuning
T103)
which
divider
is
unlocked
and
retune
the
particular
divider
slightly;
then
bring
TI
03 back to
center
frequency
and
try
detuning
again.
Once
control
is
lose,
the
exciter will
not
pull
back
on
frequenc
y unless
Tl03
.
is
tuned
back
co
nearly
"zero"
frequency.
To
widen
the
range
of
pull-in
action, an off-frequency
detector
has been
added
which
is
covered
in
the
following
section.
5.
Off-Frequency
Detector
With
the
AFC
operating
properl
y,
che
two
fre-
quencies fed to
the
grids
(pins
1
and
7)
of
V115 will
be identical,
and
no
difference frequency
appears
at
the plate.
The
original
frequencies
and
the
sum
of
the
two
original
frequencies
are
eliminated
by C193.
If
control
is
lost, a difference
beat
appears
which
triggers
V116
and
then
closes K
101.
This
will
cause:
a low frequency sweep
of
the
oscillator
to lock
the
AFC
in.
The
pull-in
range
of
the
AFC
system
with
Off-
Frequency
Detector
inoperative
is
± 100 kc
at
che
final
frequenc
y,
and
with
the
Off-Frequency
Detector
operating
it
is
± 350 kc.
To
test
the
operation
of
the
Off-Frequency Decec-
cor, switch
AFC
to
the
off
position
and
a
djust
T103,
(top
adjustment)
for
stationary
circle
on
the
CRT
in
phase
detector
position.
Then
detune
T 103 (top
adjustment)
to give a circle
"moving
around"
several
times
per
second.
This
should
close K10 I;
if
necessary
adjust
RI
74:
With
AFC
ON,
detune
Tl03
until
a
reading
of
+4o
is
obtained
on
MlOl
in che +
AFC
position. Switch
AFC
OFF
and
then
ON
again.
The
AFC
should
be re-established
within
a few seconds.
When·
the
circle becomes
stationary,
the
opening
of
KlOl
will cause a
slight
"
jump"
which can easily be
observed.
Repeat
the
above
step
in
the negative direc-
tion. As a final check,
modulate
the
transmitter
130%
with
50 cycle tone.
This
should
not
c'Iose
~101.
To
check
the
range
of
the
vernier
control
(
top
of
TI03),
bring
it all
the
way in
and
read ±
AFC
vole-

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age (e .g., + 25) then take it all the way out and read
AFC voltage again (e.g., - 15). The sum of the
absolute value of both readings should be 40 or more .
If this range is not obtained, loosen lock-nut on
handle and unscrew the handle to allow deeper pene-
tration of vernier core. Then reset locknut.
To check quickly whether VlOl and Vl02 are
properly modulating the carrier, feed a + IO db sig-
E-19
nal
at 30 cps to }101. (This will produce 2.45 volts
across J10
l; .62 volts from pins 5 to 3 at XZ 101;
.08 volts
from terminal 6 to 15 of Tl0l; and .245
volts
from terminal 4 to 14 or 10 to 13 of T 101.)
This modulation should cause very noticeable broad-
ening of the circle on the CRT in the PHASE DET.
position. A 30 cps voltage can also be found (use
Oscilloscope) at junction of L108-Rl68 as well as
at pin 5 of Vl 15.
NOTES

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E-20
Cl05
V1O8
VIO2
VIOi
VlO3
VIO9
TlO3
VIO4
TlO5
VIO5
VIIO
TlO6
LIO5
VIII
VIO6
TIO7
Tll4
VlO7
Cl37
Cl39
LIO9
C2O0
TIO4
TIOI
ZIOI
Rl85
Vll8
SIOI
Rl83
·
Figure
E-11.
BTE-1
OB
FM
Exciter, Front View
92203
YIOI
LlO8
YIO2
Vll7
SlO5
SIO6
Vll2
Lll2
Rl74
Vll5
Tl
II
.
Tll5
Vll5
TIIO
C202
TIO9
Vll6
Vll4
TIO8
MIOI
LIii
SIO2
C2OI
SIO4
SIO3
Tll3
LIIO