RCAVICTOR AR-88D User manual

GENERAL PURPOSE
C O M M U N I C AT I O N S R E C E I V E R
MODEL AR.88D
INSTRUCTIONS
H.zym
Manufactured by
RCA VICTOR DIVISION
OF
RADIO CORPORATION OF AMERICA
Camden^ N. U. S. A.
H. ZUUR
KON. WILH. LAAN 510
VOORBURG
PrInitd In U. S. A. IB-259S7-3

Figure I—Front View of AR-88 Receiver
11i»I

TABLE OF CONTENTS
Page
Title
Technical Summary
Introduction
Equipment
Description
Circuit Arrangements
Performance
Installation
Operation
Maintenance and Alignment Procedure
Mechanical Construction. ..,.
4
5
I
5II
III 5
6
IV
V7
VI 8
VII 8
VIII 10
IX 13
XParts List ;
Vibrator Power Supply Unit, MT8319
14
XI 25
ILLUSTRATIONS
Figure 1Front View of AR-88 Receiver........
Figure 2Diagram of Rear of Chassis.. ,
Figure 3Diagram of Front Panel
Figure 4Diagram of Top of Chassis.
Figure 5Loudspeaker
Figure 6AR-88 Chassis
Figure 7Top View of Chassis
Figure 8Top View of Chassis —Covers Removed
Figure 9Bottom View of Chassis
Figure 10 R-F Unit . . . . .
Figure 11 Schematic Diagram
Figure 12 Selectivity Curves . . . . . . . .
Figure 13 Fidelity Curves . . .
Figure 14 AVC Curves
Figure 15 Vibrator Power Supply Unit. .,.....
2
6
8
11
16
17
18
18
19
20
21
22
23
24
27
TABLES
Table 1Performance Data ...
Table 2Tube Socket Voltages. ,
4
14
I
A

GENERAL PURPOSE COMMUNICATIONS RECEIVER
MODEL AR.88D
TECHNICAL SUMMARY
Electrical Characteristics
Frequency Range—total 6bands
Band 1
Band 2
Band 3
Band 4
Band 5
Band 6
Maximum Undistorted Output—approximate—2.5 watts
.. 535 to 32,000 k«
.. 535 to 1,600 k.
.1,570 to 4,550 ki
.4,450 to 12,150 kc
11,900 to 16,600 kc
16,100 to 22,700 kc
22,000 to 32,000 kc
Output Impedance—2.5 ohms and 600 ohms.
Power Supply Requirements
Line Rating
or Batteries
or Vibrator Power Supply Unit
Power Consumption—100 watts.
Tube Complement
R'F and LF Amplifiers
1st Detector (converter)
Oscillator
2nd Detector
Noise Limiter
A'F Amplifier
Power Amplifier
Beat Frequency Oscillator
Rectifier
Voltage Regulator
Mechanical Specifications
Overall Dimensions
100'117, 117-135, 135-165, 190-230, 200-260 volts, 50/60 cycles.
6 volt “A” battery and 250 to 300 volt “B” battery.
MI-8319.
5RCA-6SG7
1RCA-6SA7
1RCA-6J5
1RCA-6H6
1RCA-6H6
1RCA-6SJ7
1RCA-6K6GT
1RCA-6J5
1RCA-5Y3GT
1RCA'VR'150
19!4 inches wide x11 inches high x19J4 inches deep
TABLE 1-PERFORMANCE DATA
(Approximate Values —Taken on Sample Receiver)
Antenna Input in
M i c r o v o l t s f o r 2 0 D B
Signal-Noise Ratio
Antenna Input in
M i c r o v o l t s f o r 6 D B
Signal-Noise Ratio
Sensitivity
in Microvolts
fo r 0.5 watt
Image
Ratio
Band
Megacycles
No.
Greater than
1,000,000
4.6
.9
.5
.6
1
8.0
1.4
.9
1.0
1,000,000
240,000
12.02.2
1.0
1.5
5.0
1.0.6
1.7
2
4.8
.95.6
3.0
14,5004.5.9
.6
4.3
60,000
8.0
1.3
.8
4.6
3
6.81.2
.8
8.0
2,0006.01.1
.7
11.5
4,000
1,500
6.6
1.31.2
12.1
4
7.01.2
.7
16.4
1,000
7.0
1.3
1.3
16.4
5400
8.01.4
.8
22.5
400
8.0
1.52.5
22.5
6200
7.01.3
1.2
28.0
I'F rejection at 600 kc is 100,000.
4

GENERAL PURPOSE
COMMUNICATIONS RECEIVER
I
INTRODUCTION
used, resonating well below the band with a200 mmf
antenna.
The second quality of areceiver, selectivity, is nec'
essanly acompronaise with fidelity of the reproduced
signal. This receiver is designed to have five degrees
of selectivity, three of which include acrystal filter.
To secure good frequency stability, rugged con-
struction of parts and wiring in the high frequency
heterodyne oscillator circuit has been included in the
design. This, together with voltage stabilization of
the oscillator plate supply, temperature compensation,
and proper oscillator excitation, provides ahigh de¬
gree of stability.
Reliability depends to alarge extent on the quality
of material and workmanship. Throughout the AR-88
Receiver the best material obtainable is used for each
particular purpose and all workmanship is of the best.
The following instructions should be studied before
the installation or operation of this equipment is at¬
tempted, in order that optimum performance may be
obtained.
In the design of ahigh frequency radio receiver,
are four important qualities for consideration:
1. Usable sensitivity.
2. Selectivity.
VFrequency Stability.
4, Reliability
mere
The sensitivity of this receiver is limited only by
the tube noise originating in the first tube and its asso¬
ciated circuits Alarge part of this noise is due to
"shot” effect and thermal agitation in the first tuned
circuit. Asignal, to be readable, must produce avolt¬
age on the grid, of the same or greater order of mag¬
nitude than this inherent noise voltage. Therefore, an
efficient coupling system between the antenna and the
first R-F tube of the receiver is of great importance.
This has been the subject of considerable develop¬
ment, and the system used on this receiver gives opti¬
mum coupling with antenna or transmission line im¬
pedances of 200 ohms, over the entire frequency
range of the receiver, except on the broadcast band
On the broadcast band, a. low frequency primary is
II
EQUIPMENT
or loudspeakers, an antenna system, and an AC source
of power, batteries, or Vibrator Power Supply Unit
MI-8.M9. The Loudspeaker, shown in Figure 5, is not
supplied with the equipment, unless specially ordered.
It may be obtained separately as MI-8303D. Head¬
phones MI-5803-6 arc recommended.
The equipment furnished consists ot tne Receiver
Chassis Assembly, including control panel and
tubes and cabinet for complete enclosure for table
mounting.
Additional equipment required includes headphones
DESCRIPTION
This receiver covers short wave, standard broad¬
cast, and CW service; its principal use is for short
wave communications. It is designed to withstand
severe climatic and line voltage variations without ap¬
preciable impairment of performance.
I t s f e a t u r e s i n c l u d e :
Mechanical Band Spread with Single Control tor
ease of tuning apreviously logged station.
Automatic Noise Limiter which automatically
limits interference to apercentage of modula-
,tion determined by the Noise Limiter Control
Noise Limiter Control for setting Noise Limiter
to operate at any desired percent modulation
Noise Limiter Switch for switching Noise Lim
Iter on or off.
Continuously variable High Frequency Tone
Control
Antenna trimmer for circuit alignment.
Crystal filter for ultra-sharp selectivity when re¬
quired
Exceptionally good oscillator stability through
normal variations in line voltage.
Four-gang Condenser giving high image ratio on
all bands.
Twelve Tuned I-F Circuits giving avery high
degree of selectivity.
Temperature compensated oscillator circuits on
all bands.
Ceramic Insulation throughout on gang conden¬
ser, sockets, range switch, and selectivity
switch.
Tuning Lock for service under extreme condi¬
t i o n s o f v i b r a t i o n .

IV
CIRCUIT ARRANGEMENTS
The circuit is shown schematically in Figure 11. It
consists of two stages of R-F amplification, first de'
tector, first heterodyne oscillator; three stages of I-F
amplification, second detector, noise limiter, second
heterodyne oscillator; A-F amplifier stage, output
power stage and power supply system.
with open link is required, this connection on the rear
of the antenna terminal board must be removed.
R-F Amplifier —The R-F Amplifier is designed to
provide ample selectivity ahead of the first detector
for minimizing cross modulation and blocking effects
from strong interfering signals and for obtaining a
high degree of image signal suppression. The amplifi'
cation is adjusted to provide optimum signal-to-noise
ratio by making noise contributions of circuits follow'
ing the first tube negligible in comparison with the
noise contributed by the first R-F grid circuit; that
is, each tuned circuit in the receiver contributes some
Input Coupling—^The antenna coupling system is
designed to provide optimum coupling from a200
ohm transmission line, except in the broadcast band.
The first tuned circuit is provided with atrimmer con-
denser adjustable from the front panel. This insures
ANTENNA COIL INDUCTANCE
A D J U S T M E N T S F O R
FREQUENCY BANDS
V O L T A G E T A P S W . ML4
(nooKc
^2 6o6k\\WAVEtrap
o00 o
600 OHMS
\
PLUG
(^7l5,L6
OUTPUT
4600 KC C Z2A00KC
A
4o(^0
L7,L L I 0
^O
o
1/2 345 U.IOOK 16.400 KC
R-880G
a n t - G N D . T E R M B O A R D2 . 5 O H M S T R A N S M I T T E R D I V E R S I T Y
RELAY
POWER CORD
Figure 2—Diagram of Rear of Chassis
the proper tuning of this circuit with
system.
For the standard broadcast band, conventional
tenna and ground connections should be used.
The antenna terminal board is provided with three
terminals (see Figures 2and 6), two of which may
be joined together with alink. When asingle wire
antenna is used, the link should be closed and the
antenna connected to “A.'
should be connected to “G.
balanced input, is used, the'link should be opened and
the line connected to terminal "A” and the
terminal.
IMPORTANT—Receivers are shipped from the fac¬
tory with a/ permanent bus-wire connection on the
rear of the antenna terminal board, between the
ter and ground terminals. If balanced input operation
noise voltage, but by making the gain of the first tube
as high as practicable, the noise contributed by suc¬
ceeding circuits is unimportant.
.Band Spread —The mechanical band spread with
single control knob enables the operator to quickly
tune apreviously logged station. The log scale on the
main dial and the separate vernier dial provide for
exact logging and tuning.
First Heterodyne Oscillator —The first heterodyne
oscillator is aligned to track with the R-F Amplifier
at 455 kc higher than the signal frequency, thus pro¬
ducing a455 kc intermediate frequency in the first
detector plate circuit which is amplified further in the
I-F stages. The oscillator voltage is regulated by the
RCA VR-150 regulator tube to provide maximum
frequency stability under conditions of variations in
power supply voltage.
any antenna
an-
If aground is used, it
If atransmission line or
center
cen-
6

100% modulation and to continuously lower percent-
ages down to any modulation whatsoever, determined
by the setting of the noise limiter control.
Anoise limiter switch in conjunction with AVC
provides for use of the noise limiter on CW or on
modulated reception when interference is present.
Output Tube —The RCA 6K6GT output tube is
Resistance coupled from the A-F amplifier, an RCA
6SJ7 tube, and operates into an output transformer
which has taps for matching into a2.5 or' 600 ohm
load, or into headphones. The headphone winding is
designed so that amaximum of approximately 10
milliwatts of power may be delivered to 20,000 ohm
phones. Terminals are provided pn the rear apron for
the 2.5 and 600 ohm impedances. The output from
the 600 ohm winding is fed
terminals, neither of which is grounded. This wind¬
ing may be used to feed abalanced 600 ohm line. The
output from the 2.5 ohm tap is fed to the 2.5 ohm
terminals through atwo-position jack mounted on
the panel. The headphone winding also connects to
the jack. With the phone plug inserted into the jack
in the first position, the phones are in parallel with
the 2.5 ohm output and both are on. When the plug
is pushed into the second position, the phones are
connected to the phone winding and the 2.5 ohm
output is cut off from the rear terminals. If no load
is connected to the 2.5 or 600 ohm output terminals,
the phones should always be used in the second posi¬
tion; as under this condition aload resistor is shunted
across the 2.5 ohm tap to maintain impedance match¬
ing of the system.
Power Pack —The power pack mounted on the
receiver chassis consists of apower transformer, rec¬
tifier tube RCA-5Y.5GT, and filter. Atap switch is
provided on the rear apron for changing the power
transformer voltage tap. (See Figures 2and 6.) The
voltage for which the switch is set may be read di¬
rectly on the switch. The instrument may also be
operated from 6V. “A” and 250 to 300 V. “B” bat¬
teries, or Vibrator Power Supply Unit MI-8319.
Shielding —Interstage shielding is provided to in¬
sure stability under all operating conditions and to
minimize oscillator radiation., Complete external
shielding prevents coupling to any portion of the cir¬
cuit except through the antenna circuit.
Intermediate Frequency Crystal Filter —The first
detector plate circuit is tuned to the intermediate fre¬
quency and abalanced link circuit is used to couple
the first detector plate and first I-F grid circuits. A
455 kc crystal is connected in one arm of the link cir¬
cuit and aneutralizing capacitor is connected in the
other. The impedances of the coils in the link circuit
●'jned so that the crystal selectivity character¬
istic .not impractically sharp. The band width at two
times resonant input may be adjusted to 400 cycles,
1,500 cycles, or 3,000 cycles. For this adjustment see
“Operation.”
Intermediate Frequency Amplifier —Three stages
of I-F amplification are used; RCA-6SG7 tubes are
used in all stages and an RCA-6H6 tube is used for
AVC and second detector. The first I-F Transformer
has its primary and secondary tuned, and is coupled
through the crystal filter link. The second and third
I-F Transformers are composed of four tuned circuits
each. These circuits are varied in coupling by the
selectivity switch. The fourth I-F Transformer has
two tuned circuits.
The third I-F stage is not connected to the AVC
nor to the manual volume control so that agood AVC
characteristic with little overload distortion is ob¬
tained. This also permits the CW oscillator to be
coupled to the grid circuit of this stage, giving acom¬
paratively high detector excitation voltage with small
electrical coupling to the oscillator circuit.
Second Heterodyne Oscillator —The second het¬
erodyne (CW) oscillator is atriode RCA-6J5 tube
which is electrostatically coupled to the final I-F stage.
Apanel control is provided by means of which the
frequency of the heterodyne oscillator and resultant
audio beat note may be varied.
Particular care has been taken in the design of the
circuit constants to minimize oscillator harmonics.
Automatic Volume Control —The AVC voltage is
obtained from the second detector, an RCA-6H6 tube.
Avariable delay is obtained depending on the setting
of the R-F gain control.
The second heterodyne (CW) oscillator excitation
voltage is just lower than the A'VC diode bias voltage
so that it does not decrease the sensitivity of the
receiver.
Manual Volume Control —Two manual volume
controls are provided; an audio gain control which is
employed when the AVC is in use, to obtain the de¬
sired output level, and an R-F gain control.
Noise Limiter —The noise limiter circuit utilizes
an RCA-6H6 tube and limits the noise interference to
are
directly to the 600 ohm
Tuning Meter —The necessary wires for connect¬
ing atuning meter in the cathode circuit of the first
I.F. tube have been included in the cable wiring. If
and when meters become available, it will be asimple
operation to install atuning meter. A5milliampere
meter with zero deflection to the right is required.
V
PERFORMANCE
The performance data undef technical
and the data for the various artificial antenna of 200 mmf. capacity for band 1
and 200 ohms resistance for bands 2to 6inclusive.
The output was measured across aresistance of 2.5
ohms connected in place of the speaker voice coil.
The selectivity switch was placed in position 2.
summary
curves, are approximate
values taken on asample receiver. Variations in these
values are to be expected because of practical manu¬
facturing tolerances. The data were taken with an
7

VI
INSTALLATION
sion line except on the broadcast band where alow
frequency primary is used.
For general use it is recommended that astraight
wire antenna between 25 and 50 feet long be used.
Speaker —Terminals for connection of aloud'
speaker are indicated in Figures 2and 6. The output
transformer is designed to match aspeaker having
2.5 ohms impedance.
Headphones —Ajack is provided on the left of
the front panel for plugging in apair of headphones.
There are two positions of the plug.
1. Half way in—for reception on both speaker
and phones.
2. Fully in—for phone reception only.
S e e " C I R C U I T A R R A N G E M E N T ” " O u t p u t
Tube."
Mounting —The instrument may be placed on a
table or mounted on arack. For rack mounting loosen
the panel mounting screws and remove the panel and
chassis complete from the cabinet. The panel is
equipped with standard slots for rack mounting.
Power Supply —The power supply circuit is in-
tegral with the receiver. Determine line voltage and
frequency and check with the rating of the receiver.
The power transformer primary may be connected
for any one of five voluge ranges by means of atap
switch. This switch is located in the rear apron of the
receiver, and the voltage for which it is set may be
read directly on the switch.
For Battery or other Supply Operation —For con-
nections see Schematic Diagram Figure 11. It is only
necessary to remove the plug from the socket on the
rear of the receiver, and connect the batteries to the
proper terminals as indicated by the schematic dia¬
gram. Abattery cable terminating in an octal male
plug is necessary for this purpose. Avibrator power
supply MI-8319 is available which will operate the
receiver directly from a6volt storage battery. For
information on this power unit see Section XI.
Tubes —Inspect the chassis before applying power
to see that all tubes are firmly seated in their respec¬
tive sockets.
Antenna —The input impedance at the antenna
terminals is designed to match a200 ohm transmis-
V-
VII
OPERATION
Figure 3illustrates the dials and control knobs.
VERNIER
TUNING
]
N O I S E L I M I T E R
TONE
,A.V.C. N.L.
^●A.V.C.
MAN.N.L.,-
MAN.*
OFF ♦
1*
RANGE R.F.GAIN AUDIO GAIN SELECTIVITY NOISE LIMITER
AND A.V.C.
POWER TRANS.
RECEIVE p h o n e s
R-8790
Figure 3—Diagram of Front Panel
8

DIALS
The Vernier Tuning Dial is in the center and has
ascale with arbitrary calibrations for exact tuning
and log records of particular communication stations.
It is used in conjunction with the log scale on the
main tuning dial to give additional figures for logging.
The Main Tuning Dial is on the left and consists
of adisc \:th seven scales, one for each of the six
bandsandalogscale.TheStandardBroadcastBand
calibrated in kilocycles and the other five bands in
megacycles.
is
CONTROLS
2. NL on, AVC out —Manual gain —for CW
with interference.
3. NL and AVC on —for Modulated Reception
with interference.
4. AVC on, NL but —for Modulated Reception
—no interference.
R-F Gain Control —This continuously variable
sensitivity control is for use in conjunction with the
audio gain (Volume) control for all manual gain op'
eration. With AVC on, it should as arule be set to
its'fully clockwise position or may be turned to elimi¬
nate interference.
Power-Transmit-Receive Switch —This is afour-
position switch. Starting from fully counterclockwise
these positions are;
1 . P o w e r o i f .
2. Transmit position which gives energized tube
filaments, open plate circuits, and shorted ter¬
minals for transmitter relay on the speaker
terminal board on the back of the chassis.
Connect relay to these two terminals for
transmitter operation. See Figure 2.
3. Normal reception.
4. CW reception —Beat frequency oscillator
switched on.
Noise Limiter Control —This control sets the in¬
strument for operation at the required percenUge
value of Noise Limitation. The fully clockwise posi¬
tion limits the noise interference to 100% modulation.
As the knob is turned counterclockwise, the noise in¬
terference is limited to continuously lower percentages
of modulation so that in the fully counterclockwise
position the Noise Limiter is operative on any modu¬
lation whatsoever. Normally, the fully clockwise posi-
will be used, but under extreme conditions of
Selectivity Switch —This is afive-position switch
and the band widths and control of selectivity are
illustrated in the curves of Figure 12. The five posi¬
t i o n s a r e :
I-F band width for High Fidelity, modulated
reception.
I-F band width for normal modulated recep¬
tion.
Crystal Filter in—for CW telegraph or sharp
modulated signal reception.
Crystal Filter in —for sharper CW telegraph
reception.
Crystal Filter in
reception.
1.
2tion
interference abalance point should be found for
maximum intelligibility of signal with best modula¬
tion and least noise.
3.
4. Tone Control —This is acontinuously variable
control for reducing HF response. In the fully clock¬
wise position the full tone is obtained and as turned
counterclockwise, high tones are lessened. Set it to
suit the particular tonal conditions for the signal being
received.
Beat Frequency Oscillator Control —This control
is normally used for CW code signals. It should be
adjusted to give the desired audio pitch after the
signal has been accurately tuned.
for sharpest CW telegraph
5.
Noise Limiter-AVC Switch —This is afour-posi¬
tion switch and starting from the fully counterclock¬
wise position these are:
1. AVC and NL out —Manual gain only —for
CW —no interference.
9
A

TUNING
For functions of controls see the foregoing para¬
graphs.
10. Reset Selectivity and Sensitivity (R-F Gain)
C o n t r o l s a n d N o i s e L i m i t e r C o n t r o l i n a c ¬
cordance with requirements due to inter¬
ference, station transmission, and other con¬
ditions.
11. Set Tone Control for preferred tone.
12. On CW operation set Power-Transmit-Re-
ceive Switch to "Rec. CW” (position 4) and
set BFO Control to give desired pitch.
l.L If the receiver is subject to vibration, the tun¬
ing may be locked by turning clockwise the
knurled screw directly beneath the tuning
knob. Turning the screw moderately tight
will lock the tuning.
Diversity Reception —Connect together the ter¬
minals marked “diversity,” Figure 2, on two or three
of these receivers, and equip each receiver with a
separate antenna. The “diversity” terminal is con¬
n e c t e d i n s i d e t h e r e c e i v e r t o t h e AV C c i r c u i t s . T u n e
as explained.
1. Turn recei v e r o n a n d set the Po w e r - Tr a n s m it-
Receive Switch for the required type of
operation.
2. Set Range Switch for band required.
S e t A n t e n n a T r i m m e r f o r m a x i m u m b a c k ¬
ground noise.
4. Set Selectivity Switch for the required oper¬
ating conditions —See Selectivity Curves —●
Figure 12.
5 . S e t N o i s e L i m i t e r - A V C S w i t c h f o r t h e r e ¬
quired operating conditions.
6. Set R-F Gain Control fully clockwise.
7. Set Audio Gain Control about halfway.
8. Tune in the station.
9. Reset Audio Gain Control to give desired
volume.
VIII
MAINTENANCE
This receiver should maintain its correct factory ad¬
justments over areasonably long period of time.
Causes of trouble and the probable sequence of their
development are outlined in the following paragraphs:
Anoticeable decrease in the
sensitivity of the receiver usually indicates worn
out vacuum tubes. If the sensitivity is low, re¬
move and check the tubes in areliable tube
tester or substitute new tubes one at atime.
See Technical Summary, and Schematic Dia¬
gram Figure 11. Tube socket voltages are given
in Table 2on page 14.
2Range Switch —Aswitch may operate defec
tively on certain positions after long periods of
inoperation. Usually rotating the switch back
and forth several times will clean the e.bntacts
and operation will become normal.
Abad range-switch contact is likely to cause a
change in the sensitivity of the receiver, or the
frequency of areceived signal, as the switch is
moved back and forth slightly in acertain fre¬
quency band position. Afurther check is to
turn the switch and on at one particular fre¬
quency band several times and note the ap¬
parent sensitivity of the receiver each time the
switch comes into position. The sensitivity
should be the same each time and may be ade¬
quately judged for this test by listening to the
receiver background noise.
1Vacuum Tubes
3. Circuit Alignment
Alignment Tools —Special tools for align¬
ment of R-F and I-F circuits are provided. They
are mounted in fuse clips on either side of the
gang condenser cover, and are available after
removing the large R-F unit cover. The shorter
one of the two is for adjustment of all R-F and
I-F coils, and the longer one is for adjustment
of the plunger type trimmers. One end of this
tool is for turnin’g the lock nut on the trimmers
and the other end has ahook for engaging in
the hole in the end of the plungers. After ad¬
justment, the lock nut should be securely tight¬
ened.
10