Hammarlund SP-600-JX-17 Troubleshooting guide

SP-BOO -JD.7
COIOlUNICATIONS RECEIVER
FOR
SINGLE AND DIVERSITY RECEPTION
INSTRUCTION AND SERVICE IlANUAL
,"
Checked by library ..
----.......-::=
THE HAWARLUND MANUFACTURING CO. INC.
460 W. 34TH st. New York 1, N. Y.

SP ... 600-JX17
COMMUNICATIONS RECEIVER
INSTRUCTION AND SERVICE MANUAL
TABLE OF CONTENTS
SECTIONS
~
Title
Paae
I
INTRODUCTION 2
II
CIRCUIT DESCRIPTION
4
III
INSTALLATION
7
IV
OPERATION
9
V
MAINTENANCE
13
VI
ALIGNMENT 17
VII
REPLACEABLE PARTS LIST
33
ILLUSTRATIONS
Figure
Title
f!e
-
1..
Front Panel
1
2. Block Diagram
23
3.
Top View or Chassis -Alignment Adjustments
24
4.
Audio and ridelity Curves
24
5.
Selectivity Curves
26
6. Rear
View of Chassis
27
7.
Top View of Chassis
28
8. Parts Identification for Locating Test Points
29
9. Schematic DiagraJn
30
10.
Connection Diagram-Receiver Chassis
31
11. Tuning Unit Con~ection Diagram
32
12.
Crystal Control Unit Connection Diagram
33
TABLES
No.
Title
~
-
1.
Tube Socket Voltages
21
2.
Tube Socket Terminal Resistance
22
3.
RF and HF Oscillator Al~gnment Frequencies
and Adj~stment Designations
25
4. Approximate Signal Input at IF & AF Stages
for 20 Volts Output
25
1.

20
2879 4
13
3
12
5
21
19
16 6 22
10
II
14
17
18
15
1.
"SEND" "REC" switch 6.
"BAND CHANGE" control
15.
"A VC" "MAN" switch
2.
"IFO" "EXT" "INT" switch
7.
"MEGACYCLES" window 16. ccMETER"
CCRF" UAF" switch
3.
CCHFO" "V:AR" "EXT" "XT ALS" 8.
Main tuning dial
17."
"MOD" "CW" switch
"1" "2" "3" u4" u5"
9.
V ernier dial
18. uBEATOSC"
control
"6" switch 10.
"TUNING" control
19.
USELECTIVITY" switch
4. UBFO-AVC" UEXT BFO" uSLOW" uFAST" 11. .
"TUNING LOCK" 20.
"XT AL PHASING" control
uINT BFO" "SLOW" uFAST" switch 12. Plastic
chart
21.
"LIMITER" "OFF" switch
5.
"PHONES" jack 13. uHFO"
"6 FREQ'~control
22.
"AUDIO GAIN" control
14.
"RF GAIN" control
Figure J. Rac/io Receiver, Front Panel View
1.

SECTION I
IBTBODUCTION
The SP.600-JX17 is a2O-tube superheterodyne radio communications receiver des1gi1ed
specifically for diversit1 reception. The receiver is intended tor use as either
the "master" or "slave" \Ulit tor the reception of MCW, CW, suppressed carrier, or
frequency-shitt signals,
"Master-slave" relationship is established by interconnecting two or more
receivers. These connections may be made between the beat-trequency and/or the
heterodyne oscillators ot eaCh receiver, or between the receivers and an externally
connected master oscillator comqan to each.
Frequency drift, after a15 millute warm-up, ranges between ,001 percent and
.01 percent of frequency, depending on the frequency used. '!'his is an unusual
degree
of frequency stability for variable tuned SF oscillators and closely approaches
crystal stability.
The trequency control unit provides for fixed channel crystal-controlled opera-
tion on any six trequencies within the range from. 75 to 54 megacycles. Front panel
controls permit the selection of either the normal high stability, continuously
variable tuning or fixed frequency operation. For crystal-controlled fixed-channel
operation, it is only necessary to set the dial to the signal frequency, switch to
the crystal frequency desired, and tune with the delta frequency control. Desired
crystals may be purchased on special order from the Hammarlund Manufacturing Company,
The selectiVity control prOVides 3degrees of crystal and 3degrees of non-
crystal selectiVity ranging from sharp (,2 Kc) to broad (13,0 Kc), The crystal
filter in the SP-600-JX17 embodies the same circuit features that have proved so
effective and desirable in Hammarlund Super.Pro receivers,
Two stages of radio frequency amplification are prOVided on all bands: single
conversion is used for signal frequencies up to 7.4 megacycles, and double conversio~
employing a crystal-controlled oscillator, tor signal frequencies above 7.4 mega.
cycles.
Four stages of IF amplification, detector and AVe rectifier, noise limiter and
meter
rectifier, beat frequency oscillator and butfer amplifier, IF output, AF
amplifier and output power stage, are among the features of the SP-600-JX17, Which
are discussed fully under separate headings in this manual,
The Audio output circuit is designed for a600-ohm load or line and is provided
with a four-terminal split winding for balanced load operation. Maximum power out-
put is approximately 2_0 watts. The headphone circuit when referred to an 8,OOO.ohm
resistive load provides signals attenuated approximately 15 db below the 6oo-ohm
power
output. Either headphones, loud speaker or both may be used for reception ot
signals.
The receiver i,t. output or audio-output, connected to a sui~able frequency-shift
receiver converter and associated teletypewriter, prOVides tor recorded copy ot a
teletype s1gnal. A ~N signal may be amplitUde-modulated by an external tone
generator connected to the receiver, so that a steady, audible (monitoring) tone is
always heard when the transmitter carrier is on the air, whether signal intelligence
is present, or not.
A single tuning control of special design permits maximum traverse speed as well
as exceptional operating ease~ It controls both the main and vernier dials. The
main dial, in addition to ~eing frequency"ca11brated, includes an arbitrary scale in

hundredths, while the vernier 8cale contain8 an arbitrary Ical. in units. 'ae ..
arbittary Icales, cOlIIPlemented by the anti-backlash gear tra1D which governa 4ial
movement, provlde extremely accurate 10881ag and resetab1l1 t7 ,A tuniq lock .Isure.
positive lockil18 action without affecting the frequency 8ettiq.
Radiation i8 negligible and cQmplies with· requirements tor ship.board operation
and tor multi-receiver installations.
Althoup the anten~ input circuit is de8igned tor the coaxial cable eODDectlon
ot awave antenna system, a conventional single vire antenna _y be used,
The selt-contained power supply of the SP-600-JX17 1e designec1 tor. operation on
a single phase 50 to 60 cycle alternating current power source. The power trans-
former primary 1s prOVided with terminals otterina a range ot line voltage trom 90
to 270 volts.
The send-receive switch desensitizes the receiver but leaves the power au to
provide tor instant reception between tr~sm1ssions,
The SP-600-JX17 is available as e1 ther a r$ck model, sui table tor amounting in
a standard 19" relay rack, or as a cabinet model tor table use"

SECTION II
CIRCUIT DESC1UPTION
General
The electrical circuitry ot the SP.600-JX-17 is sho~ schematically 1n Figure 9.
A block diagram, Figure 2, is provided to illustrate the arrangement and functions
of the various circuit sections. The location of the vEtrioustubes is shown in
Figure 3. The circuit for single conversio~, used for signal frequencies up to 7.4
megacycles, consists of two stages of RF amplification Vl and V2; First Mixer V5;
First Heterodyne Oscillator V4; four"stages of IF ~lificat1on, V7, V9, V10 and
Vll; Detector, AVe Rectifier V14; Noise Limiter V15j Beat Frequency Oscillator V13i
IF output and AF amplifier, v16A and v16B; Output Power Stage Vl7, and the Pavel'
Supply System which includes BPower Rectifier V19, CBi.as Rectifier C20 and Voltage
Regulator v18.
In the circuits for double conversion, used tor signal frequencies above 7.4
megacycles the Second Mixer v6 and Second Heterodyne Oscillator Va are substituted
tor the gate tube V7.
A precise rotary turret 1s used to change bands. It associates the RF tuner,
sub-assemblies of the antenna coupling, the tt~-stage RF amplifier, and the first
heterodyne oscillator of the band selected Ynth the circuitry in the RF strip common
to each band. In this way, each RF tuner SUb-assembly i$ positioned directly
adjacent to :its respective tube and gang section of main tuning capacitor ClA-ClH.
Input Couplin§ ... The antenna input coupling provides an optimum match for a95-
ohm coaxial cable line connected to antenna input connector Vl. On bands, 1, 2, 3,
and 4, the antenna RF transformer is secondary-tuned by dual section ClA-C1B of the
main tuning capacitor; on bands 5and 6, by section C1A only. A capacitor, such as
C3 tor band 1, is used $0 that the antenna circuit tracking matches that of the RF
amplifier.
RF Amplifier - The Vl and V2 stages of the RF amplifer are identical, Vl is
secondary-tune£by dual section C1C-ClD while V2 is secondary-tuned by dual section
ClE-C1F of the main tuning capacitor. Complexed coupling is used in RF stages to
maintain a more constant level of signal gain over the frequency levels of each band.
High image rejection ratios are achieved through the use of three High Qtuned RF
circuits and by double conversion on the three higher fre~uency bands. The high
gain developed by two RF stages assure~ maximum sensitivity at high signal-to-noise
ratios.
First H~odyne Oscillator (variable v4) - First Heterodyne Oscillator v4
functions as a Colpitts oscillator for the three higher frequency bands and as a
tuned-grid oscillator tor the three lower frequency bands. Dual section C1G-ClB ot
the main tuning capacitor provides for the variable tur~ing of the oscillator. For
single conversion, the oscillator frequency is 455 Kc higher than the signal fre-
quency, While for double conversion the oscillator frequency is 3.955 mc higher
than the tuned.in signal.
First Heterodyne Oscillator - (Crystal Controlled V3) -For services reqUiring
extremely stable, fixed-fre~uency operation, a crystal controlled high frequency
oscillator is provided. Instant change-over from variable to crystal controlled
oscillator with achoice of six crystal positions is effected by a front panel XTALS
control. Asecond front panel control marked Delta Frequency permits a tolerance
adjustment of the crystal Qscillator frequency over the + .005~ (purchased crystal
tolerance) range. ~
4,

For double conversion, the conversion oscillator output from V3 is augmented b
v4.
Conversion oscillator· output from V3 is availablt at HFO output connector sockt
J8 at the rear of the frequency control unit when the front panel control is in a
crystal position; but when the front panel control 1s set to its EXT position, the
conversion oscillator voltage for the receiver is that Which is externally connecte
to J8.
Intermediate Frequency Amplifier ~ Single conversion to 455KC is employed for
signal frequencies below 7.4 met There are four" stages of IF amplification in~
corporating the Hammarlund ~ patented filter circuit. Six positions of selectivity
provide 6 db bandwidths of .2, .5 ... 1.3, 3 .. 8, and 13 kc. On the three narrower
bandwidth
positions the crystal tilter is in operation. The crystal phasing control
provides extreme selectivi~y for the high attenuation of closely adjacent inter-
fering signals. Double conversion 1s employed for signal frequencies above 7,4mcs.
The signal is heterodyned to 3.955 mc by the First Mixer V5 and Heterodyne Oscilla-
tor v4, or V3 for high image rejection. nle 3.955 mcs signal is then heterodyned
to 455 KC by the Second MixerV6 and the 3.5 me Fixed erystal"Controlled Oscilla-
tor Va for selectivity. For double conversion, the tUlled circuits and the 3.955 mc
IF transformer T2 assure appropriate input to the Second Mixer v6. IF transformer
Tl in the plate circuit Of V5 is reson~nt to both 455 kc and to 3.955 mes. For
single conversion, the 455 ke signal path is to 455 kc IF gate V7j for double
conversion, the 3.955 me signal path is to Second Mixer v6. The prime function of
V7 is to render the 'signal path through it an open circuit for double conversion
and available to the signal for single convf:rsion.
The 3.5 mc crystal-controlled heterodyne output from v8 is available at IFO
connector socket J6 at·the rear skirt of the receiver, when the front panel IFO
switch is set to its INT position; but when the !FO switch is set to its EXT posi-
tion, the 3.5 mc conversion oscillator for the receiver is that externally
connected to J6, since vB is now inoperative.
Detector and AVe - The V14 tube is used as a high level Detector and AVe
rectifIer. The AVe circuit is provided with separate time constants for OW and MCW
operation. Ave and Diode output terminals provide for connections in diversity
applications. The AVC bias developed is applied to Vl, V2, v6, V7, and V9, but the
bias to Vl and V2 is reduced through use of a voltage divider network (resistors
R48 and R53). .
The BFO-AVC switch provides choice as to a FAST or SLOW time constant. Since
the switch functions also as aBFO switch, two positions, BFO FAST and BFO SLOW, are
provided.
Beat Frequency Oscillator ~ The beat fre~uency oscillator employs a high
capacity Colpitts circuit which provide a high order of frequency stability and
minimizes oscillator harmonics. The Beat Frequency Oscillator Vl3, is coupled into
the detector circuit through Buffer Amplifier V12, which eliminates oscillator lock-
in. A tront panel control varies the audio-beat frequency from zero beat to +3kc•
..
The beat frequency oscillator output from V13 is available also at BFO connector
socket K7 at the rear apron of the receiver when the front panelBFO switch is set
to either its FAST or SLOTt1 INT BFO positions; but when set to either of its FAST or
SLOW EXT BFO positions, the functioning beat frequency oscillator for the receiver 1s
that which 1s externally connected to J7, since the output from V13 is suppressed.
Front panel switch control MOD-CW renders V13 operative for CW operation. An
external switch control connected to terminals Br ot remote connector socket

AN3102A-14S-2S (J4) on the rear skirt may also be used to perform this fl~ction,
since.these terminals are 10 parallel with the contacts of the control switch.
Alternate to the use of the beat frequency oscillator to render a keyed-carrier
CW signal 'intelligible, a local tone generator may be externally connected to
terminals Aand B of J4 to amplitude mod\1late the ew signal. fl"'he use of a local
tone generator prod\1ces a steady tone even ~'hen the received carrier frequency
drifts .J4 is furn1shed with connector plug Aand 3l08B-14S-2P and cable clamp
AN3057-6.
Noise
Limiter ~ The noise limiter circuit V1S limit~ the noise interference
trom IgnItion systems or other sources of pulse-type noise, Asepar.ate limiter
control switch permits optional use of the limiter on any mode of operation when
pulse type interference is present.
Audio Frejuency Amplifier - A resistance-coupled amplifier triode v16B amplifies
the audio-frequency signal from the detector.
Audio Output - The audio output to V17 is transformer-coupled through a split
balanced winding to deliver 2.0 watts undistorted output to a600-ohm load. The
split balanced winding permits balancing of the direct kind in the output circuit,
as used for teletype or similar service. A separate secondary winding provides
attenuated audio signal output for headphone operation. This winding will deliver
an output of 15 milliwatts into an SOOO-ohm resistive load when the 600-ohm power
secondary
is delivering 500 milliwatts to a600.ohm resistive load.
IF Output. Acathode follower, the v16A provides a 70-ohm impedance source of
intermediate frequency (455kc) to socket SO-239 on the rear skirt of the chassis.
Plug PL-259, and angle plug adapter M-359 used with coaxial cable RG-l~/U are
not supplied.
Power Supply ... The power supply is an integral part of the receiver, It in-
cludes the B rectifier V19 and C rectifier V20, together with their respective low-
pass filters and Voltage Regulator v18. The power tran~former is provided with
screw terminal primary taps, covering apower line source range of 90 to 270 volts,
50 to 60 ~ycles. The power transfol~er and filter components are protected by fuses
in the primary and plate supply circuit.
Tuning Meter - The tuning meter is used on AVe operation to indicate the accurac
of tuning and the relative strength of rece!ved signals. Depression of the Meter
Switch
converts the meter circuit for. indication of output level in db from 6 milli-
watts.
RP Gain Control and Power Switch • The RF gain control is provided for manual
control of sensitivity to preve~erload1ng on s~rong sigpals when operating with
the AVe-MANUAL switch in the "MA.'iUAL
ll
position. This control also operates when the
switch is- tn the "AVel! position. The Power "ON-OFF
lI
swit!;b is operated at the
counter-~lockwise extremity of the RF gain control.
Send-Receive Sv~tch - The send-receive switch desensitizes the receiver but
leaves the power "ou
if
to provide for instant recept.ion between transmission periods.
Radiation -Advanced design and shielding of the high frequency, second conversiOl
crystal and beat frequency oscillators has reduced radiation to a negligible point
so that interference of this nature, co~n in multi~~eaeiver in~tallations, is
reduced to a minimum. .
6.
"

SECTION III
INSTALLATION
Tubes and Packing ... After unpacking the receiver see that all tubes are firmly
in their sock~t6 and that all packing material is removed fronl the receiver.
"Power SUB1Y ... Make sure that the primary tap lead at the bottom of the power
transformer sconnected to the tap which most nearly agrees with the 50 to 60 cyclf
power source voltage. Power connector plug AN31.0BB ... 18 .. 3S with cable clamp AN3057-1C
with power cord and plug are ~Jrnished wtth the receiver.
Antenna - The input impedance at the antenna socket, 80-239, is designed to
match a95-ohm coaxial cable line. The plug connector PL.259, and angle plug
adapter M-359, sUFplied with the receiver, are for use with RG ... ll/U coaxial cable
(not supplied).
Speaker - The speaker should be of the permanent-magnet dynamic type and should
include a speaker voice coil to 6oo-ohm line-matching tranoformer for connection to
the 600-ohm audio output terminals of the receiver. Caution: When the 6oO-ohm out-
put is not used connect a600 .. ohm, 2-watt resistor to these terminals to avoid
component damage from
higb transient peak voltages. For applications requiring the
insertion of direct current control or indicating voltages, the jumper connecting
the two balanced sections of the 600 ohm-output may be removed and the insertion
circuit, such as alow resistance balancing potentiometer, connected in its place.
Headphones ... Either high or low impedance headphones may be used by plug
connection to the phone jack located at the lower left side of the front panel. The
high impedance type is recommended.
Mounting -
The receiver is designed for rack mounting, Top and bottom cover
plates are supplied for mounting in a standard 19-i~ch rack. The panel is lOt
inches high. See Section VII, The receiver should be placed in a position which
permits the free access of air.
Crystals for Frequency Control • Crystals Y1 to Y6 are not supplied with the
receiver, but will be supplied on special order for any signal frequency within the
range of from 2 to 30 megacycles. In order to insure correct crystal-controlled
frequency operation, crystal units may be ordered from THE HAMMARLUND MFG. CO. INC.
The order should specify the ~.!! freq.uency for which each unit is to be used.
See
note at end of Table 5. To instaIl crystals loosen the knurled thumb screw on
top of the Crystal Control Unit T34 and push to the rear. Insert the crystals in
the sockets~ Bring the retainer spring assembly forward so that the springs press
on top of the crystal holders, and tighten the thumb screw. Mark the" signal fre-
quency for Which each crystal was selected in megacycles Oll the plastic chart
provided for this purpose alongside the crystal switch 82. Pencil or ink may be
used and can
be erased if it is desired to change these figures at any time. The
numerals on the chart should be used so that they agree with the numerals on the
crystal socket positions, which are also indicated by the crystal selector switch.
Relay Connections - If external relay operation for the send-receive function
is desired, connection may be mnde by soldering atwin conductor cable to the
terminals of the Send-Receive s~itch S9. In this case 89 is left in the Send or Open
position.
AVC and Diode Output. In diversity appltcations, the diversity feature is
l.ccentuated by interconnecting the AVe (.) bus between receivers" and utiliZing a

common ground (G) connection. This AVe connection is made when the IF or AF outpu~
of th~ system is used to provide tor the intelligence due to a CW, MCW, or fre-
quency-shift signal; but for voice signals only the audio output from one receiver
is used. This is done by removing the DIODE OUTPUT jumper on each receiver apart
from one; and connecting the negative (-) terminal of each to that of the one whosc;:
terminals remain Jumpered.
IF Output - The IF output socket 60-239 at the rear skirt provides the signal
at 455kc for diversity receiving system uSe. Connector plug PL-259 e.nd angle plug
adapter M- 359 (supplied) should be used with RG-ll!U coaxial cable (not supplied).
Th~ output provided to a10-ohm resistive load 1s approximately 200 millivolts for
normal sensitivity (2 microvolts input signal).
Master Slave Connections - In diversity applications the monitoring requirements
imposed on
the operator are severe, but may be kept at a mlnim~~ by use of common
conversion and beat-frequency oscillators. Then the operator need concern himself
mostly with the signal level 1n each channel and the signal tuning af the receivers.
To provide for V-3 crystal-controlled first heterodyne, and/or v-8 3.5 mc.
crystal-controlled heterodyne I and/or V-13 beat-freqUency oscillator output,
respectively, from the master to the sluve receiver, tile HFO) lFO, and BFO sockets
80-239, at the rear skirt of each, furnished with plug PL-259, and angle plug
adapter M-.359 for IFO and BFO only, a.re interconnected. 'l~e coaxial cable RG-ll/U
suited for use is not supplied.
With the red tront panel controls in each instance on one receiver set to a red
panel marking, that receiver becomes the slave receiver, wherein its V .. 3 (HFO),
V-13 (BFO) and its v-8 (IFO) are rendered inoperative.
Remote Connector - The REMOTE connector J4 1s furnished with connector plug
AN 31oSB-14S-2P and cable clamp AN 3057-6. lIse terminals Aand B of J4 for
connecting a local external tone SOUl"Ce to modulate a CW signal and use terminals
eand D of J4 to perform the function of the CW-MOD 6,\-11 tch by another system panel
switch, 1f desired.
8,

SECTION IV
OPERATIO!
General •Before attempting operation of the SP-600-JX11 receiver, the operator
shouid thoroughly familiarize himself with the functions and uses of the various
controls. When referring to the controls in this description, the words in capital
letters represent the part of the name adjacent to the control on the front panel
or on the rear skirt of the chassis" FOr example, when referring to the SELECTIVITY
control, the word, SELECTIVITY i~ capitals indicates the legend appearing adjacent
to the control. Reference to photographs, Figs. 1and 6, is suggested while
reading this description. Front panel controla and dials are shown in Fi~. 1and
rear controls and terminals are shown in Fig. 6.
Selectivitl"control • The SELECTIVITY control 1s a 6-posit1on switch which
selects three crystal' and three non-crystal degrees ot selectivity, ranging from
extremely sharp tor CW reception to broad for gOOd fidelity MCW operation. The
SELECTIVITY control dial indicates the 6 db bandwidth at each setting.
Phasinf Control .. The CRYSTAL PHASING control is So differential type, variable
air capac! or'. It permits adjustment ot the cry~tal selectivity characteristic for
high attenuation of closely adjacent channel interference on either side of the
signal frequency.
RF Gain Control - The RF GAIN control varies the overall gain of the receiver.
This contro! is operative in either position of the AVC-MAN switch.
Power Switch - The power, or "on-oft" switch is combined with the RF GAIN con.
trol. Complete counter-clockwise rotation ot the RF GAIN control throw~ the power
switch to the "0 ft" position, as indicated on the RF GAIN control dial.
Audio Gain Control" The Audio Gain control varies the input voltage to the'
audio amplifier. This control is also operative in either position of the AVe-MAN
switch.
Phone Jack - The PHONES jack is a single circuit jack operating with the sleeve
grounded and is suitable to receive any standard single circuit phone plug. It is
in the circuit at all times and is connected to a separate secondary winding of the
audio output transformer, which provides an attenuated signal for headphones. See
Section III, Installation.
Audio Output - The AUDIO OUTPUT is available- at the tour-screw terminal board
at the rear of the chassis tor connection to a600-ohm load. See Section III,
Installation.
Noise Limiter - The LIMITER control switches the noise peak limiter in or. out
ot the circuit. This control is operative independently of any position of any
other control. See Section II, Circuit Description.
AVC-Manual Switch - In the AVC position the AVC-MAN switch applies automatic
bias potentials to the controlled RF and IF amplifier tubes, thereby holding the
audio output relatively constant over awide variation in the strength of received
signals, This min~mizes the variation ot output due to fading of the received
signal and prevents blasting and overloading when tuning through signals of greatly
different strength While traversing $frequency band. In the AVC position the RF
Meter circuit is operative tor indication of tuning resonance and relative strength
ot received signals. The RF GAIN eontrol is operative on AVC operation when necessau,y

to control exceptionally strong signals or to reduce noise, but the RF meter is
less effective when the RF GAIN control is below maximum setting. In the MAN posi-
tion the Av.e potential is re1J1Oved from the controlled tubes and the gain of the
receiver is manually controlled by the RF GAIN control.
OW-Modulation Switch - The eW-MOD contro~ i~ the OW posit1Qn energizes the beat
frequency oscillator_ In MOD position the beat frequency oscillator is inoperative
and the conditione are established tor either voice modulated or tone modulated
signal reception.
Beat Freque,ncy Oscillator - The BEA~ OSC control vartes the tun1~g of the 455 kc
Beat Frequency Oscillator over arange from zero beat to plus or minus 3 kilocycles.
BFO-Ave Switch - The BFQ.Ave control in either the EXT BFa SLOW or INT BFO SLOW,
positions connects an additional timing capacitor to the AVe circ~it to accommodate
the AVe circuit to automatic CW keying, as compared to either the EXT BFO FAST or
INT BFa FAST positions, effective for MCW and freq~ency~shift reception. In either
FAST or SLOW INT BFa positions, the internal BFO of the receiver is operative When
the eH-MOD swiCth is at C"!. In either FAST or SLotoJ' ~1CT BFa posit1ooQ1 the BFO source
connected to the BFO connector at the rear skirt is useQ by the receiver~
Iro Switch - The IFO am tch in the IN'!' posi tion render~ the internal 3,,5 me
crystai-coQtrolled oonversion oscillator operative. In the EXT position the
oscillator is inoperative, since the !FO of th~ master receiver (externally connect-
ed to the IFO connector at the rear skirt) 1s used.
Send-Receive • The SEND-REC control is a single-pole single-throw toggle switch.
In the SEND position it desensitizes the RF amplifier, gate, second mixer and 3.5 mc
oscillator tubes during transmission periods.
Tuning Control and Dials - The TUNING control rotates the main tuning capacitor
as well as tne main and vernier tuning dials. The main dial has six frequency band
scales, calibrated in megacycles, and an arbitrary outer scale. The vernier dial
has an arbitrary 0 to 100 scale. The nu~eral under the upper or fixed pointer of
the main dial indicates the number of complete 'revolutions that have been made by
the vernier dial at any setting. Thus, if the pointer for the outer scale of the
main dial indicates over the fig
1
lre "4" and the vernier dia.l ind1cates 87.6, the
reading to log tor this setting is 1\487.6". This precise mechanical vernier system
divides the rotation of the main dial over each frequency band into apP~oximately
600 vernier divisions, with one-halt division caliQration points. Since it is easy
to estimate one-tenth divisions on the vernier scale, this divides each frequency
band into approximately 6000 readable settings, providing extreme accuracy in the
logging and resetting of stations,
Tuning Lock - The TUNING LOCK
1
located to the right of the TUNING control, pro-
vides a positive lock for the tuning mechanism without affecting the frequency
setting when it is desired to prevent accidental shifting of the tuning,
Band Chan,e -Each revolution of the BAND CHANGE control turns the turret, con-
taining the Rand HF Oscillator coil, trimmer and switch contact assemblies, trom
one frequency band to the next, The turet has no stops and may be turned in either
direction. A positive detent mechanism assures correct location ot the various bands,
The BAND CHANGE control simultaneously operates the ~mall MEGACYCLES band 1nd1pat1ng
dial, located at the center of the panel and aligns the dial frequency indicator
with the proper scale ot the main dial.
Crystal Controlled HlP Oscillator' -'rne 'Cl'ALS control selects one variable high
frequency oscillitor operatlQn~ anyone ot the six crystal positions. Correspondingly
10,
I

numbered crystal sockets are provided in the Crystal Control Unit. In its EXT
position, the crystal-controlled first conversion oscillator source is connected to
the BFO connector at 'the rear skirt. See Section III Installation. The DELTA
FREQ control compensates for the small crystal frequency. tolerance.
Meter Switch - The METER switch i$ a. qoubl,e-pole, doub~~-throw to!gle sw1t~h
with spring return to the RF position. See Section II, Circuit Deseription, '!'un1ns
Meter.
Tuning Meter Controls -
The. ME'l'ER ADJ RF control 1,s ue$ed to adJ,ust the re6ist&ll~e
shunting the meter When the METER switch ~s in the norma)., or RF position. It is
adjusted to produce a reading at plus 20 db on the RF scale of the lIeter, with a
10 microvolt RF input signal and with tne AVC-MAN switch in the AVC position.
Depression ot the METER switch to the AF position converts the meter circuit for
indication of the AF pqwer output level in db trom 6 milliwatts. This switch is
spring-returned to the RF position when released and should not be depressed for
the AP scale unless the audio output has been adjusted tor low power output by means
of headphones or speaker. Failure to observe this precaution may result in damage
to the meter. The. meter AT)J AF control is used to regulate the meter current when
operating on the AF sca.le. Thiq control is adjusted to obtain a0 db :rea.ding on the
AF scale of the meter and is lJ1$de with the auQ.io power output from the 600-ohm AUDIO
OUTPUT terminals adjusted to 6 llil11watts, or 1.9 voJ.ts across a 600-ohm resistive
load.
prelim1n*t to Operation - Turn the power switch "on" by turning the RF GAIN
control cloc se arid advance this control to "10". Note that the dial lamps light.
Place the SElID-REC sri tch on REC and turn the BAND CHANGE c9ntrol to thetrequency
band in whicb it is desired to operate. Tbis should be done at least 15 minutes
before using the receiver in order to permtt the tubes to warm up, Insert the head-
phones
plug tn the PHONES jack or us~ speaker as desired. See Installation, Section
III.
Mew Reception -Turn the TUNING LOCK to its extreme counter-clockwise position
and turn the SELECTIVITY switc~ to 3 kc. Put the CW-MOD switch on MOD, the LIMITER
switch to OFF, the AVC-MAN. switch on AVC, the XTAL PHASING control at its center
position and turn the XTALS switch to VFO. With the BAND CHANGE control in the
proper position for the 'frequency band desired, as indicated by the MEGACYCLES dial,
advance tbe AUDIO GAIN control until some noise is heard. Turn the TUNING control
to indicate the desired frequency on the main dial and tune the signal for maximum
response or indication on the RF Meter. At resonance the main dial reading should
be within one-quarter ot one percent ot the signal frequency. Re-adjust the AUDIO
GAIN control for the desired output le~el and as required to prevent overloading.
Carefully tighten the TUNING LOCK by turning clockwise, if desired. The SELECTIVITY
switch may be turned to the 8kc or 13 kc position for improved high frequency
response if the signal-to-noise ratio is sufficiently high. It the noise level is
high, the SELECTMTY switch should be turned to tbe band",Tidth which provides the
most
inte.l11gible reception and the LIMITER switch should be thrown II on" • It the
SELECT~ITY switch is used on One of the XTAL pO$itions, the XTAIJ PHASING control
may be adjusted to either side of its center position to attenuate an adjacent
interfering signal. The RF GAIN control may be turned down somewhat to reduce noise
during stand-by periods in the transmission when traversing the tuning range, or
during deep fades of the signal. The RF Meter scale ca1iQration is tor maximum RP
GAIN control operation and indicates only when the AVC·MAN switch is on AVe. When
searching for very weak signals the CW-MOD switch may be thrown to OW sod the BEAT
OSC control set at "0". Loca.te and tune the signal to obtain zero beat and then
throw the CW-MOD switch back to MOD.
The Crystal Frequenc;y Coptrol MY be used for fixed-frequency operation at any
11.

signal frequency tor which crystals have been provided. See Section III, Installa-
t,ion. Turn the XTALS switch to the numeral corresponding to that on the panel chart
tor the desi~ed signaltrequency. Set the main tuning dial to the s1gnal tre~uency
and adjust the 6 FREQ control to obtain zero beat with the CW.MOD switch on CVT and
the BEAT OSC control at "0". Throw the eW-MOD sn tch to MOD and adjust the TUNING
control for maximum RF Meter indication or for maximum response.
ew Reception - The preliminary procedure tor CW reception is the same as for
MCt,T reception above. Place the Ct.-I-MOD switch on ew and with the BEAT esc control
at "0"Itune the desired signal for zero beat, Adjust the BEAT ase control, in
either direction, to obtain the audio pitch desired. The AVe-MAN switch may be used
in the position Which gives the best reception. Adjust the desitedoutput level by
the AUDIO GAIN control when on Ave and by the RF GAIN control when on MAN. The RF
Meter does not operate on the MAN position. The SELECTIVITY switch may be used in
the XTAL positions, as found desirable, to reduce noise or to provide rejection of
an intertering signal. The XTAL PHASING control is adjusted for minimum interference
from an adjaeent, interfering signal. It interference of this kind persists, fur-
ther discrimination between the desired and the undesired signals may be realized by
slightly detuning the desired signal to the opposite side of resonance from that on
Which the undesired signal is located and readJ"sting the XTAL PHASING control and
the BEAT OSC control for the desired .signal. 'lbe Crystal Frequency Control may be
used as described under MeW Reception above.
It reception is to be suspended and resumed at short time intervals, the power
should be left "orr' and for such operation the SEND~REe switch should be thrown to
SEND between reception periods. This keeps the receiver ~arm and ready tor instant
use.
When operation ot the recei.ver is ~ompleted, turn the power "off" by extreme
counter-clockwise rotation of the RF GAIN control,

SECTION V
MAINTENANCE
General - Th~s receiver is designed for continuous duty and should normally
require lIttle attention beyond the replacement of tubes. An occasional cleaning
of the gear teeth in the gear train is recommended to prevent aheavy accumulation
of dust which may cause calibration error and improper operation of the gears, This
may be done with asmall stift bristle brush, turning the controls to obtain access
to the different portions ot the gears. No grease or oil should be used on the
gears. Operation and maintenance ot the receiver will be greatly facilitated if
the contents of this instruction book are thoroughly digested.
Some sectionalizing of faults is po~sible, if the fault is not existent on all
of the frequency bands. Non operation of only the three lower frequency bands,
indicates that tpe fault is associated with the circuits of tube V7. If only the
three higher frequency bands are affected, the tault is associated with the circuits
of v6 or v8. If only one single band is affected, refer to SF Oscillator and RF
Coil Assemblies in this section.
Visual evidence of trouble is usually aburned or darkened resistor, which is
usually the result of excessive current due to a short circuited capacitor or tube
element on
the load side of the resistor. In such a case, the short circuited
capacitor or tube and the resistor should be replaced as indicated. Refer to
Figures 7 to 12 and Table 5 for location and values of components. If the checks
on
tubes, fuses and visual inspection fail to disclose the fault, the tube socket
voltages and resistances should be measured and checked against the value given in
Tables 1and 2. Any appreciable departure beyond anormal variation of approximately
15 percent from the values in the£e tables will generally indicate the component or
circuit at fault. If the foregoing does not reveal the fault
lthen a
stage by stage
check of amplification should be made as shown in table 4. Any great difference
from the values of input shown in the table will indicate the stage at fault. Ifa
tuned circuit component, such as an IF transtormer, RF or IF oscillator coil assembly
is found defectivel only the replaced unit need be realigned, Follow the alignment
procedure in Section VI, for the unit involved.
The IF Transfo~ers, Crystal Filter, Beat Frequency Oscillator and the 3.5 me
Crystal Controlled Oscillator assemblies are mounted on the chassis, independently
of their respective shields. The shield can assemblies are easily removed for
inspection of these units, without disturQing the soldered connections. v~en re-
placing these shields, make sure that the grounding springs are in place on the
inductance adjuster screws before the shield is installed.
Vacuum Tubes - Weak or defective vacuum tubes are the most common cause of
decrease in sensitivity, faulty performance or failure of operation in a receiver.
In case of such faults, first remove the tubes and check them in atube tester of
reliable design. If atube tester is not available, substitution of a new tube for
each tube type and position should be tried. See Figures. 2and 3, Such substitution
is best made, one tube at atime in order that the faulty tube may be detected by
the improvement or restoration of performance by the new tube.
Locating Faults - If the dial lamps do not light when the power switch is turned
on, check for ablown line fuse, F1 and replace it at the rear of the receiver from
the spare fuses. If the dial lamps light but there is no sound at all in the head-
phones
or speaker, check for a b~own, minus B fuse, F2, If blown, replace. In
replacing fuses, make sure th~t only a1.6A Fusetron is inserted in the line fuse
holder and that only a3/8 ampere tuse is inserted tn the minus B tuse holder.

Should neither tuse be blown, or it replacemebt of the fuses does not restore
operation, the receiver should be removed from its rack and inspected for visual
signs of trouble. The- rack .model receiver is provided with bottom and top cover
plates which should be removed for purposes at inspection and repair.
IF Transformers - If a fault is traced to one of the variable coupled IF trans-
formers, T4 or ~, check Whether the fault exists on all positions of the selectivity
switch 55, or only on one position of this switch. If the "faulty operation occurs
on only one switch position, check for continuity of the coupling coil associated
with that position, check for imperfect soldered connections at the coil and switch
terminals and check the switch contact involved. If faulty operation localized at
one transformer exists on all positions of the selectivity switch, make the con-
tinuity check on the plate coils, on the main srid coil and on the wiring associated
with these coils. Transformers T4 and T5 and Crystal Filter T3 have additional
inner shield assemblies that are held in place by the tension nuts on the adjusting
screws. To remove these shields, hold the adjusting screw with ascrew driver to
prevent turning the screws and losing the alignment adjustment and loosen the
tension nuts, using another small screw driver engaging one of the slota. When
replacing these shields and tension nuts, employ the same method and tighten the
tension nuts just enough to prevent the adjusting screws from working loose,
Beat Fresuency Oscillator • To remove the beat fre~lency oscillator T6
1
it will
be necessary to settne crystal selector srNitch 82, on its number 3 position and
loosen the four set screws in the rigid shaft coupling and the two set screws in
the disc on tbe selector switch shaft. Slide the switch shaft forward thro~ the
coupling and disc. It may be necessary to remove burrs, caused by the set screws,
from
the switch sbaft in order to slide the shaft through the disc. Now loosen the
four set screws of the flexible coupling on the B~'O shafts and slide the coupling
forward
on the BFO drive shaft in the front panel. Remove the BFO shaft bearing
bracket by taking out the tvro screws bolding it to the chassis. Unsolder the leads
from the six terminals of the BFO unit at the underside of the chassis. Be careful
to avoid overheating the.wire of. the. shielded cable ~ince this wire is insulated
with pol st ene and is easily dame. ed by heat. Note that if' this cable w-1re is
groun e to its sh e , t ere w" e 00 eat frequency voltage input to the buffer
tube Vl2 even though the beat oscillator is functioning properly. Therefore, with
the shielded lead disconnected from the lug of the BFO unit, checl with a continUity
or ohmeter the connection of this wire to the buffer tube V12 and its freedom from
the chassis. Carefully observe the wiring of the BFO unit for correct replacement.
See T6 on Figure 12. NoW' remove the two scret-Is holding the BFO shield can to the
chassis and the two screws ~t the underside of the chassis and remove the BFO unit.
When replacing the unit, follow the reverse procedure. Before tightening the two
screws holding the unit to the chassis and the two screws holding the shaft bearing
brackets, adjust the unit and shaft brackets to obtain alignment of the two shafts
at the coupling. Make sure that the shield grounding spring is in place, with the
bow of the spring dOvmward against the tension nut,. before replacing the shield can
assembly.
Adjustment
of BFO -With the AVC-MAN switch on AVC, and the SELECTIVITY control
on the .2 kc position, tune in an unmodulated signal for maximum tuning meter reading.
Set the CW-MOD switcb to CW and with the BEAT OSC dial at 0, adjust the top screw of
the BFO unit for zero beat. Turn the BF~T OSC dial to each 3kc position and check
the output beat frequency against a known audio frequency source such as agood audio
oscillator. If the beat frequencies obtained at each 3kc position is not within the
range between 3and 3.5 kc, loosen the set screws of the BFO shaft coupling and turn
the shaft of the BFO with respect to the drive shaft and repeat the above, resetting
the 0 adjustment by the top screw of the BFO unit each time until the above range is
realized. One set screw should be used juet tight enough ~o allow the drive shaft
to operate the BFC shaft until the range is correct and then tighten both screws.

••
Crystal Switch Adjustment - If~ the mechanical drive of the crystal control
switch has been disturbed, it should be adjusted as follows: Carefully slide the
switch shaft·through the disc and into the rigid coupling and, being careful not to
turn the switch, tighten the four set screws in the rigid coupling, with the knob
indicator on the number 3 position as originally set under Beat Frequency Oscillator.
Now set the crystal switch on the number 1 position and, holding the disc in a
counter-clockwise direction so that the end of the slot in the disc is against the
drive pin, lightly fasten the set screws of the disc. When this disc is properly
adjusted on the shaft, with the switch 1n the number 1 position, the connecting bar
between the two discs should not be under tension and should exhibit a slight amount
of play when tried with the thumb .and forefinger. When rfO adjusted, tighten the set
screws.
Crystal Control Unit. If it has been determined that the Crystal Control Unit
is detective~ it will be necessary to remove the unit for repair or replacement.
Reter to Figure 11 and 12 and unsolder the lead of resistor R71 from switch S3 on
the gear plate. Unsolder the black, black-white, blue-red and rei-white leads of
the crystal control unit from terminal strip E13 underneatn the chassis and unsolder
the red lead of the unit from filter capacitor c16l. Remove the XTALS switch shaft,
as described under Beat Frequency Oscillator. Loosen set screws and remove the
del ta C control knob. Remove the nut and 10ckw8sher at the top of the bracket post
adjacent to the power transformer and remove the bracket over the filter chokes.
The front end of this bracket is slotted and engages agroove in amounting post of
the crystal ,control unit. Remove the four screws that secure the filter assembly
panel to the mounting posts at each corner of this panel and move the filter assembly
sufficiently to permit removal of the four scr~ws holding the crystal control unit
to the chassis. When these screws are removed, the unit may be taken from the
receiver. In removing the unit and in subsequently handling it, be careful to avoid
strain on the delta C shaft, or the delta C capacitor may be damaged. Remove the
four screws holding each of three sides of the cQver and spring the two top ends of
the cover enough to make the flanges clear the top of the box. Hold these flanges
apart to prevent their edges from damaging the RF chok.es in the unit while sliding
the cover off the crystal unit box. When the unit is to be replaced, follow the
reverse of the above procedure. Follow tbe procedure under Crystal Switch Adjust-
ment to properly reinstall the switch mechanism.
HF Oscillator and RF Coil Assemblies ~ If faulty operation occurs in only one
frequencY' band at the receiver, the trouble should be found in one of the four coil
assemblies for that band in the tuning unit turret. For example: Coil assemblies
T13, 19, 25 and 31 should be exam1neq if' band 7.4 to 14.8 meanly, does not perform.
normally •• To remove these coil assemblies stand the receiver on its right or left
side and remove the bottom cover ple-t.e from the tuning unit. Turn the band change
control to place the band in queation in its normal operating position and then turn
the band change control two and one-half revolutions coUnter-clockwise. This will
place the band coil assemblies parallel and at the bottom of the tuning unit. Now
remove the two springs holding one coil assembly in the turret and carefully remove
it by sliding it towards you and off the tongues of' the ·shields. It is best to
remove only one coil assembly at atime and inspect it for detects or' substitute a
replacement assembly if available. Caution: Make sure that the coil base is firmly
seated ~d secured by its retaininJ sprIngs before'going to the'next assembly or
turning the band ch80§e control. allure' to do this may damage tfie switell spring
contacts berond repair. Repeat this procedure until the taul ty assembly is found.
In checking these assemblies, first check for continuity of the coils, particularly
the small primary coils as in the RF Input assemblies, which are lie-ble to d8.lll88e
if the receiver is ope:rated in the presence ot ve1';f stroUS transmitter signals, In
replacing these ~oi1 assemblies be caretut that the end ot tbe a~se~ly nearest the
coil is toward the trqnt of the receiver.
15.

Mixer Plate Coil Assembly -Trouble in the Mixer Plate Coil Assembly Tl, is
indicated if the input required at pin 7 of V5 is found to be greatly different than
the values shown in Table 4" and the g~in from pin 7 of v6 is normal. To obtain
access to the components of the mixer plate coil assemblies it is necessary to remove
the crystal control unit and the filter assembly as described under Crystal Control
Unit. The cover plate and shield of Tl may then be removed tor replacement of a
defective component., If the entire assembly is to be replaced, it will be necessary
to unsolder all of the leads at both the,bottom and top terminal boards of the unit.
Refer to Figure 11 for components and wiring of Tl.
RF Tube Platform - If the receiver fails to perform normally on any of the six
frequency bands and the previous tests indicate that performance of the IF and audio
frequency amplifiers is normal, (including the gain check in accordance with Table 4
for the input to pin 7 of V5) the fault is indicated to be in the RF Tube Platform
or in the main tuning capacitor. Before removing the RF Tube Platform, it is
advisable to remove the top shield cover and inspect the main tuning capacitor
connections. Refer to Figures 8and 11. Observe that the tuning capacitor is
operating properly when the tuning control is rotated. Using a miniature tube
adapte;, see Section VI alignment, apply a,modulated rf test signal successively
to pin'l of VI and V2 and to pin '7 of V5. For each of these positions of the adapter
and signal, tune through the proper dial setting for the signal frequency used.
Gain of the order of 5 or 6should be indicated for each stage and loss of signal
will indicate the section to be investigated for the fault. No signal output, when
the input signal is applied to pin 7 of V5, will indicate trouble in the BF oscilla-
tor section of the unit. With the covers removed :rrom the tuning capacitor and Tl"
refer to Figure 11 and unsolder the blue
l
white-black, red-White, red-green, yellow-
black and blue-red leads that come from the tube platform at the top of Tl. Un-
solder the leads from the tuning capacitor rotors, stators and ground straps at each
section. Unsolder the lead from the tube platform at 83. Turn the Band Change con-
trol one-half turn from any band position in order to have the band switch contacts
disengaged and leave the band switch in this position until the RF tube platform 1s
replaced, otherwise irreparable damage to the switch contacts will occur • Remove
the four screws at the corners of the top of the platform and the four screws at
the side flange and carefully remove the platform. In handling be careful to pre~
. yent damage to the switch contacts of this assembly. When the unit is ready to be
.teplaced, follow the reverse of the above procedure.
~n Tuning Capacitor - If it is necessary to replace the main tuning capacitor,
the procedure is as follows: Remove the top cover and unsolder the leads of the
capacitor as described under RF tube Platform. Bring the capacitor to full mesh by
means of the tuning control. Carefully remove the spring and drive link at the
front of the capacitor. Remove the single screw that secures the capacitor frame
front plate to the gear plate, looping a piece of small wire around the spacing
washer between the capacitor and gear plate. The front capacitor plate 1s located
and held in position by two dowel pins and will not move when the front screw is
taken out. Now hold the capacitor by its frame with one hand and remove the rear
supporting screw and spacer. The capacitor may now be moved to the rear, to dis-
engage the dowel pins, and lifted from the receiver. Follow the above procedure in
reverse when replacing tbe capacitor.

SECTION VI
ALIGNMENT
The alignment of amodern communications receiver requires precision instruments
and athorough knowledge of the circuits involved. Since tbis receiver is adouble
super-heterodyne type, the alignment procedure is even more involved tQan usual.
Under normal service the receiver will stay in alignment for extremely long
periods ot time, consequently realignment should not be attempted unless all other
possible causes ot a particular trouble have been eliminated. Hhen it has been
determined
that any realignment should be made, a great deal of caution should be
exercised in making the adjustments, since any required readjustment should not
entail more than a slight angular motion of the ad,1usting screw.
ALIG~ OF THE IF STAGES
The low frequency IF should be aligned first. The recommended method for
aligning the low frequency IF involves the use ot asweep frequency signal generator
and an oscilloscope. Since these 1nstruulents are not available at the average ser-
vice station the alternate method using an amplitude modulated signal generator and
an output meter will be described first. The additional intor~tion required ~or
the visual alignment method will be covered in a later paragraph.
The signal generator should be coupled to the grid of the mixer tube V5 through
a capacitance ot approximately .01 mtd. A miniature tube adapter will be required
to make the mixer grid connection available. A sui table adapter, AlB No. CV -49519,
is available as Part No. 977 from Alden Manufacturing Co., 117 N. Main Street,
Brockton, Mass, An output meter should be connected across the output or the
receiver or the speaker voice coil. The receiver controls should now be set as
follows:
Control
-
Selectivity
Send--Receive
CW--Mod
Phasing
AVe--MAN
Audio Gain
RF Gain
Band Switch
Dial
BFO-AVC
IFO
Position
See text
Receive
Mod,
Arrow
Man
Set for approx. 20 volts output
See text
1.35--3.45 mc
2.5 mc
Int. Bfa fas't
Int.
The signal generator should be modulated 30 percent at 400 cycles. Turn the
selectiVity switch to the 3kc position and advance the RF Gain control to maximum.
Set the signal generator frequency to 455 kc and adjust its output until some
deflection 1s noted on the output meter. Refer to figure 3 tor the location of the
various alignment adjustments. Adjust L42; L41, L39, L38, L36, and L32 for maximum
output, reducing the signal generator output and the RF Gain control as required to
prevent overload or excessive output. Now turn the selectivity switch to the
narrowest pos1t1on~ .2 kC, and adjust the signal generator treq~ency for the maximum
output. This establishes the correct signal frequency by the 455 kc crystal'for the
IF amplifier and the frequency of the signal generator should not be disturbed for
17.

therema1nder of the low frequency i.f. alignment, unless it should be to re-check
this establishment of crystal frequency to make sure that the signal generator
frequency haa not drif.ted during the alignment. The selectivity switch is now
turned to the 3kc position and L42
1
L4l, L39, L38, L36 and L32 are again adjusted
for maximum output. Before changing this set-up the BFO should be turned on by
throwing the Cl;<1-Mod Gyri tch to CW and checked for zero beat with the BFO knob dial
at its zero reading. If necessary L44 should be adjusted for zero output. This
check and adjustment
of the BFO should be done with the signal generator carrier
unmodulated.
The Procedure for the visual ~ethod of aligning the low frequency IF, using the
doubl~ image system, should be the same as the above except that the adjustments are
made for both maximum amplitude and coincidence of the oscilloscope images. The
oscilloscope vertical input should be connected across the diode d.etector load
resistance, trom the junction of R64 and R65 to chassis.
The high frequency IF should be aligned next. Set the band switch to the
7.4~-14.8 me band. The selectivity switch should be in the 3kc position, Adjust
the signal generator frequency to 3.955 me and adjust L31, L33, and L34 for maximum
output.
The 3.5 mc crystal used in the second conversion oscillator circuit is held to
a very close frequency tolerance and may be used as afrequency standard at mUltiples
of 3.5 mc from 10.5 mc upwards. In order to do this, in view of the complete
shielding against radiation from this oscillator, it will be necessary to temporar-
ily connect a two foot length of insulated wire to the antenna terminal and dress
the free end of this lead around the tube shield on the 3.5 mc oscillator tube v8,
This test should, of course, be removed except while in use as afrequency standard.
ALIGNMENT OF THE RF AMPLIFIER & HF OSCILLATOR
To adequately align the RF Amplifier and HF Oscillator an accurately calibrated
signal generator and a.n output meter are required. The frequencies required are
shown in table 3. The location of the adjustments is shown in Figure 3. The use
of Table 3and Figure 3should be made in following this part of the alignment ~ich
will now be de~cribed for one floequency band. The same procedure should then be
followed
for the other frequency bands.
To align the .54 .. 1.35 mc band the signal generator is coupled to the antenna
input terminal through a lOO-ohm carbon resistor. The generator should be modulated
30 percent at 400 cycles and the output meter connected across" the receiver output
terminals. The receiver controls sho~ld be set 86 follo~s:
Control
Selectivity
Send-Receive
CW·Mod
AVe-Man
Audio Gain
RF Gain
Band Switch
Limiter
BFO
Position
i
3kc
Receive
Mod
See Text
Set for approx. 20 volts output
See taxi
Set for band to be aligned
Otf
Var
18.
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