Hallicrafters HT-46 Training manual

'Bllicraliers
OPERATING AND SERVICE INSTRUCTIONS
COMMUNICATIONS
TRANSMITTER
MODEL HT-46

~ARRA.NTY
"The Hallicrafter's Company warrants each new radio product manu-
factured
by it to be free. from defective material and workmanship
and agrees to remedy any such defect
or to furnish a new part in ex-
change
for any part of any unit of its manufacture which under nor-
mal installation, use and service discloses
such defect, provided the
unit
is delivered by the owner to our authorized radio dealer, whole-
saler, from whom purchased,
or, authorized service center, intact, for
examination, with all transportation charges prepaid within ninety
days from the date of sale to original purchaser and provided that
such examination discloses in our ;udgment that it is thus defective.
This warranty does not extend to any of our radio products which
have been sub;ected to misuse, neglect, accident, incorrect wiring not
our own, improper installation, or to use in violation of instructions
furnished
by us, nor extended to units which have been repaired or
altered outside of our factory or authorized service center, nor to cases
where the serial numberthereof has beenremoved, defacedorchanged,
nor to accessories used therewith not of our own manufacture.
Any part of a unit approved for remedy or exchange hereunder will
be remedied
or exchanged by the authorized radio dealer or whole-
saler without charge to the owner.
This warranty is in lieu of all other warranties expressed or implied
and no representative
or person is authorized to assume for us any
other liability in connection with the sale of our radio products:'

Figure 1. Hol/icrafters' Model HT -46 Transmitter . 1
56 -006958
SECTION I
GENERAL DESCRIPTION
1-1. INTRODUCTION.
The Hallicrafters Model HT-46 Transmitter
is a precision built compact, high performance
transmitter of advanced design. The transmitter
utilizes nine tubes and a single signal conversion
heterodyning system for transmission of single-
sideband (88B) and continuous wave (CW) code
signals on the 80, 40, 20,15 and 10 meter amateur
bands.
The versatilit y of th e HT-46 transmitter
permits operation as a self- co ntained station
transmitter or ma y be used in c onjunction with
the Hallicrafters Model 8X -146 communications
re c eiv er as a tran s ce iver c ombination.
The transmitter is supplied with push-t o-
talk control with provision for the addition of th e
Hallicrafters Model HA-16 for voic e contr o lled
88B operation.
Amplified Auto matic Level Co nt ro l (AALC)
c
ir c uitr y within th e tr a nsmitt er he lps pr eve nt
"s pl a tt er " due to seve re "flat-t o ppin g" of th e
final amplifi er when unint e nti o nall y ove rdri ve n.
The Model HT-46 may be operated as a
complete transmitter or as an exciter for driving
a linear amplifier such as the HT-45, HT-33B,
HT-41 or others. If others are used, the y should
be capable of supplying a 50 ohm termin a tion for
the Model HT-46 transmitter.
Other fe atures of th e Model HT-46 trans-
mitter include :
• Optional operation as transceiver with co m-
panion Model 8X-146 rec e iver or as se lf-
c ontained transmitt er / e xciter unit .
• An accuratel y calibrated VFD with ex ce llent
me chanic al and temperature stabilit y.
• Const a nt tunin g rat e on all bands.
• Upper and lower sideband operati on on all
bands 80 throu gh 10 meters.
• A cr y stal latti ce filt er with 6 poles for
o ptimum sing le sideband r e sponse.
• Combinati on final amplifier plat e c urr e nt
and RF o utput volta ge met e rin g for ex act
tunin g.
• 70W to lOOW PEP o ut p ut co ver s exc it er r e-
quir eme nt for mo st 1 KW lin ea r a mplifi er s.
• Keyed RF ca r r ier for CW oper a tion with
s hapin g netwo rk in k ey in g ci r c uit.
- 1

1-2. TVI (TELEVISION INTERFERENCE)
SUPPRESSION.
The HT-46 has been designed and con-
structed to suppress spurious radiations that may
cause television interference. The TVI problem
was given full consideration in the design and
layout of the chassis. Components specifically
selected to avoid undesired resonances and
arranged to prevent parasitic oscillations have
been used.
There are, however, some types of TVI
that cannot be prevented within the transmitter
itself. This is particularly true in fringe recep-
tion areas. In such cases, a good commercial
low-pass filter connected at the transmitter out-
put is recommended. For a more complete dis-
cussion of measures that may be used to handle
special problems of this type, refer to the "Radio
Amateur's Handbook" published by the American
Radio Relay League.
IMPORTANT
Do not, under any circumstances,
attempt to operate the Model HT-46
equipment before becoming completely
familiar with the instructions contained
within this manual.
SECTION II
TECHNICAL SPECIFICATIONS
TUBES AND FUNCTIONS
Vl 12AT7
First and Second Microphone V5 12BY7A Transmitter Driver
Amplifier
V6
6HF5
Transmitter Power Ampli-
V2 12AT7
Carrier Oscillator and Third
fier
Microphone Amplifier
V7 6BA6 VFO
V3 6EAB 9 MC IF Amplifier and AALC
V8
6EA8
Heterodyne Crystal
Oscil-
Amplifier lator and Mixer
V4 6AH6
Transmitter Mixer V9 OA2 Voltage
Regulator
Tuning Ranges ................... .
Full frequency coverage of the Amateur bands in eight
ranges as follows:
80M
40M
20M
15M
*10M
10M
*10M
*10M
3.5 to 4.0 MC
7.0 to 7.5 MC
14.0 to 14.5 MC
21.0 to 21.5 MC
28.0 to 28.5 MC
28.5 to 29.0 MC
29,0 to 29.5 MC
29.5 to 30.0 MC
*Heterodyne oscillator crystals not supplied with trans-
mitter. (Transmitter will accommodate full set of
crystals.)
Heterodyne Oscillator Crystals ......... Type CR-23/U in HC-6 Holder
Band
* 7.0
*21.0
28.0
*28.5
29.0
29.5
Frequency
21,500.000 KC
25,000.000 KC
32,000.000 KC
32,500.000 KC
33,000.000 KC
33,500.000 KC
*Supplied with Model HT-46.
Types of Emission ............. . . .. SSB - Selectable USB/LSB with suppressed carrier.
CW - Keyed RF carrier.
2 -

Frequency Control ....... .
Type of Sideband
Generation ..
Transmission Control ..... .
Dial Calibration
Calibration Accuracy. . . . .
Self-contained VFO or transceive operation with Model
SX-146
receiver.
Solid state modulator with 9 MC, 6 pole crystal filter
(Nominal BW =2.1 KC).
SSB - Push-to-talk at microphone or through control
outlet circuitry. VOX control is optional ac-
cessory. (Model HA-16.)
CW -Manual. Rear key jack accepts standard 1/4-
inch two conductor phone plug. Key circuit also
at control outlet.
5 KC increments,500 KC tuning range.
Less than one pointer width error across the dial after
indexing at 3.5 MC.
Frequency Stability . . . . .. ........... Less than 500 cycles drift in first hour, after fifteen
minute warm-up, and less than 100 cycles per hour
thereafter.
Output Impedance .
Power Input . . ...
Microphone Input ..... .
Audio
Response Overall ...... .
Distortion Products . . . . . . . . . .
Unwanted Sideband Rejection ....
Carrier Suppression Capability
Power Supply Requirements ........ .
Station Control Outlet . . . . . . . . . . . . . ..
VOX Unit Receptacle ................ .
SX-146
Input. . . . . . . . . . . . . . . . . . . . . . .
Transceive Cable Impedance .. .
Number of Tubes .......... .
Dimensions Overall ........ .
Net Weight
Shipping Weight
Fixed, 50 ohms. Rear chassis mounted receptacle
accepts RCA type phono plug. (Supplied.)
SSB -175 Watts PEP Maximum
CW -150 Watts Maximum
0.005V RMS into high impedance load. Panel connector
accepts standard 1/4-inch three conductor phone plug.
500 CPS (Max.) to 2200 CPS (Min.) at 6 DB.
26 DB (Min.) below PEP reference.
50 DB (Min.) below PEP output at 800 to 2200 CPS input.
50 DB (Min.) below PEP output.
117V AC,
50/60 cycles, 350 Watts.
Rear chassis mounted eleven-pin socket accepts
Amphenol type 86-PM11 plug. (Supplied.) Provides relay
contacts, speaker muting, receiver muting, transmitter
control, etc.
Rear chaSSis mounted six-pin socket accepts Amphenol
type 71-6S plug. (Supplied with jumper wire.) Provides
power and control for VOX Adaptor, Model HA-16.
Rear chassis receptacle accepts RCA type phono plug.
(Supplied.)
Provides inter-connection for transceive
operation with Model SX-146.
75
ohms. Use Amphenol cable NO. 21-597 or equivalent.
8 plus 1 voltage regulator and 15 diodes.
5-7/8 x 13-1/8 x 11 inches (HWD).
26 pounds.
28 pounds (Approximately)
Accessories . . . . . . . . . . . . . . . . . . . . VOX Control Unit Model HA-16. Designed for quick
attachment to rear of Model HT-46 cabinet to provide
voice controlled operation. (VOX) Power is derived from
Model HT-46 through single plug-in connector. Contains
three tubes and sensitive VOX relay. Net Weight - 3/4
pound. Shipping Weight-1-l/2 pounds (approximately).
Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3 amperes, slow blow, 3 AG type.
- 3

SECTION III
INSTALLATION
WARNING
LETHAL HIGH VOLTA GE IS PRESENT
WITHIN THIS EQUIPMENT. BE CARE-
FUL WHEN INSTALLIN G THE UNIT OR
PERFORMING CHECKS OR ADJUST-
MENTS INSIDE THE CABINET.
3-1. UNPACKING .
Ca refully r emove the equipment fro m it s
ca rt on an d packin g material and examine it for
possible da ma ge which m ay hav e occurred in
transit . Sh ou ld an y si gn of da ma ge be apparent ,
im m edia t ely fil e a claim with th e c arrier st a tin g
th e extent of th e damage. Che ck all ship p in g lab els
and tags for spec i al instru ct ion s be for e r em ov ing
or destroy in g them.
3- 2. LO CATION.
Th e transmitt er ma y be installed in an y
l
ocati on that will permit free circulat i on of air
thr ough the ventil a tion openin gs in the cab ine t.
Do
not place any obj ect on top of the cab in et in
o
S X-146
INJEC T
J3
t t
•
GROUND
AN1ENNA
J4 J5
a manner that will obs tru ct normal ventilation .
Avoid exce ssiv ely warm l ocations such as th os e
near radiators and heatin g vents.
3 -3. PO WER SOURCE .
Th e Mo del HT-46 Transmitter is de si gn ed
to ope r ate from a 105/125V 50/60 cy cle AC pow er
Sour ce. Nomina l lin e voltage for tes ti ng and m ea-
surements is 117V . The o utlet should be capabl e
of
handlin g a 350 w att l oad with good re g ulati on.
IMPORTAN T
If in doubt about your powe r sour ce,
co nta ct yo ur lo c al pow er company prior
to insertin g the power cor d int o an y
po
wer ou tl et. Plu gg in g th e power cor d
int o th e wr ong source of power ca n
cause ex te nsiv e dama ge to th e trans-
mitt er .
Set th e OPERAT IO N c ontr ol at OF F (fUll
co unt er cl oc kwis e) and make all installation con -
nection s b efo r e co nnectin g th e transmitter to a
source of power .
•
PI , J6 R33
MODEL HT-46
105/125 VOLTS 50160 CPS
@\ POWER CONSUIolPTION 350 WATTS
, _'!/J
BIA S KEY f AMP
ADJ
J2
FI
156-0070 28
Figure 2. Rear View of Transmitter .
4 -

SX 146
HT-46
AHPHENDL
,----5
EXTOSC@
lY PE 21-591
q
lh
INPUT
TRANSCEIVE
SX-4~
.8
CABLE
SPKR
HUH GND
GND
ANT
1-"
ii
I ,~
,~
,~ I
SLAVE 6~\~~~ ®
®<
®
ANTENN
'\.7
I ~ ~ ~ ~ ~ ~ ~ m ~ ~
I, t UJ6 2-,lJ I 51
3
LLk.~~J:l~~H
L------J-------+-------+----t---- KEY CONNECTION
L-------+-------+---------t
i
----1I--.:;;;-;:-- (J: III
EARIH OR COLD
WATER PIPE
GROUND
RG58/U-50~
CALIBRATE SIGNAL E Xl 32 ~ Bf VAC
PICKUP LEAD SPEAKER III VAC COAXiAl
WHEN REQUIRED ANTENNA RElAY
1-" RG58/U-5DA d: A RS8tU DR RS58tU
~-"'I"":;';:';;';";;;;";~---
RT 1-"
156-007044
Figure 3. Typical Interconnections for Model HT-46 and Model SX·146.
3-4. ANTENNA_
The Model HT-46 Transmitter is designed to
terminate into a 50 ohm unbalanced transmission
line. A non-reactive load is preferred for optimum
results, however a VSWR of 2.5/1 can be accom-
modated by the transmitter with acceptable
results. Any of the popular di-pole or beam
antennas using 50 g,q.~ transmission lines will
give excellent results.
For further information on the subject of
antennas, refer to the "Radio Amateur's Hand-
book" or the" ARRL Antenna Book", both published
by the American Radio Relay League.
IMPORTANT
Some form of lightning protection should
be provided which will comply with local
code requirements.
The ANTENNA connector located on the rear
chassis apron mates with an RCA-type phono con-
nector. Use RG-58/U co-axial cable or equivalent
for feed line to a linear amplifier or antenna
changeover relay, Refer to Figures 2 and 3 for
details.
3-5. GROUNDS.
All station eqUipment should be bonded to-
gether with heavy copper wire or braid and
connected to a cold water pipe or outside earth
ground. An external chassis ground terminal is
provided on the Model HT -46 rear chassis apron
for this purpose.
1-
-- --
-,
b
1°
I
I
TIP RING SLEEVE I I
STANDARD :3 CONDUCTOR
~C~O~
':'
-l
1/4-INCH PHONE PLUG
156-007026
Figure 4. Microphone Wiring for Push- To- Talk Transmitter Control.
I
-- -- --
I
I I
0
c5
I I G
TIP
RING SLEEVE I
~
I
-
STANDARD :3 CONDUCTOR
l.!:!!C~~
-1 1/4-INCH PHONE PLUG
156·007027
Figure 5. Microphone Wiring for Transmitter Control with VOX
Control Unit Model HA-16.
3-6. MICROPHONE.
The microphone receptacle is located on the
front panel. The microphone cable should be fitted
with a standard 1/4-inch, three conductor phone
plug wired as shown in Figures 4 and 5. Any good
high impedance crystal or dynamic type micro-
phone may be used, however best results will
usually be achieved with a microphone designed
especially for voice communications use.
- 5

The microphone circuit shown in Figure 4
may also be used with VOX control, however some
microphones fitted with push-to-talk switches also
mute the microphone element until the switch is
pressed, hence VOX operation is not possible un-
Ie ss the microphone switch is altered accordingly.
3-7. KEY.
The station keyer may be connected to the
transmitter at the closed circuit key jack at the
rear chassis apron or at the CONTROLOUTLET.
Refer to Figure 3. The key jack accepts a standard
two conductor 1/4-inch phone plug. Wire the plug
so that the key base connects to the plug sleeve
which is at ground potential. Pin NO. 90f the CON-
TROL
OUTLET maybe used to key the transmitter
with Pins NO.1 or NO. 8 used for ground connec-
tion to the keyer.
When the keyer is plugged intotheKEY jack
the keyer circuit must be closed for SSB or CW
tune up in the CW-TUNE position of the OPERA-
TION contro1.
When the
keyer is wired into the CONTROL
OUTLET, insert a dummy phone plug into the key
jack to hold the circuit open for CW operation.
3-8. SX-146 INJECT.
Transceive type of operation is made avail-
able when a 75-ohm co-axial cable is connected
between the Model HT-46 transmitter and the
Model SX-146 receiver.
The cable is connected between the SX-146
INJECT receptacle on the transmitter and the
SLAVE OUTPUT connector on the receiver after
removing the 82 ohm dummy load plug in the
receiver receptacle. The cable may be any con-
venient length to reach between the units and
should be made up of 75-ohm co-axial cable with
RCA-type phono
plugs at each end. Small diameter
75-ohm co-axial cable made by Amphenol Corp
(NO. 21-597) is recommended. Do not use shielded
microphone type cable for this application.
3-9. CONTROL OUTLET.
The control outlet circuitry mayor may not
be required by the station installation. A typical
station wiring circuit is shown in Figure 3. Note
that the following facilities are available at the
control outlet.
6 -
Speaker muting: Pins NO.2 & NO.8 and
NO.7 & NO.1.
Receiver muting: Pins NO.6 and NO.8
Keying circuit: Pins NO.9 and NO.8
PTT control circuit: Pins NO. 10 and NO. 8
SPDT relay contacts: Pins NO.3, NO.4
AND NO. 5
Calibrate signal coupling: Pin NO. 11
3-10. FUSE.
Specifications: 3 amperes, slow blOW, 3 AG
type.
3-11. ACCESSORY INSTALLATION.
1. 10 Meter Band Crystals: Three addi-
tional crystals will be required for full 10 meter
coverage. To install the crystals it will be neces-
sary to remove the top portion of the cabinet
(Refer to paragraph 7-2). Chassis markings will
indicate their location. The crystals required are:
BAND FREQUENCY
PART
NUMBER
28.0 32,000.000
KC
019-201963
29.0 33,000.000
KC 019-201965
29.5 33,500.000 KC 019-201966
2. VOX Control Unit Model HA-16: The
Model HA-16
adapter unit is available to provide
voice control operation of the Model HT-46 Trans-
mitter. It is installed on the rear of the trans-
mitter cabinet as follows:
A. Remove the jumper plug (PI) pre-
sently installed in the VOX UNIT socket located
on the rear chassis apron of the transmitter.
Save the jumper plug for it must be replaced if
the control unit is disconnected.
B. Loosen the ground bolt at the rear
of the transmitter and space the flat washers
about 1/8 inch apart.
C. Hook the Model HA-16 VOX control
unit into the two key holes in the rear cabinet
wall just above the ground bolt and insert the
notched flange between the flat washers of the
ground bolt. Tighten the ground bolt nut.
D. Plug the inter-connecting cable of
the control unit into the VOX UNIT socket. The
unit is now ready for adjustment and operation.

SECTION IV
FUNCTIONS OF OPERATING CONTROLS
4-1. TUN ING CONTROL.
The tuning control is used to vary the fre-
quency of the VFO to select the desired frequency
of transmission when the transmitter is used as
a separate unit. (VFO switch at XMTR.) When
operating the transmitter as a transceiver with
the Model SX-146 receiver (VFO switchatRCVR)
this control is disabled and the frequency of trans-
mission is controlled by the receiver.
Note that the frequency increases from left
to right for two bands whose numbers appear above
the calibration marks. For the remaining bands
logged below these marks, the frequency increases
from right to left.
The BAND SELECTOR setting indicates the
lowest frequency of the band or band segment being
tuned.
4-2. OPERATION CONTROL.
The OPERATION control is a six position
switch which controls the mode of transmission
as follows:
POSITION
OFF
STBY
USB/LSB
(Two positions)
CW-TUNE
FUNCTION
Removes all primary power
from the transmitter.
Application of primary
power places both heater
and plate voltages on the
tubes which are biased off
in a stand-by condition. The
transmitter control relay
permits the receiver cir-
cuits to function at this
time.
In these two pOSitions the
transmitter is placed in
operation for single side-
band suppressed carrier
mode of transmission. The
color code indicates USB
or LSB for the band in use
and is so coded on the BAND
SELECTOR panel mark-
ings.
This position places the
transmitter on the air with
carrier only to permit tun-
ing the transmitter for SSB
operation. In this same
position, the transmitter
may also be keyed for CW
operation.
STBY
4-3. MIC GAIN.
This is a second stand-by
position which retains the
heater and supply voltages
and again permits the re-
ceiver circuits to function.
This control sets the audio level to the
balanced modulator stage from the microphone
audio amplifier stages. The control has sufficient
range to handle any high impedance high or low
level microphone deSigned for voice communica-
tions.
4-4. DRIVER TUNE.
The DRIVER TUNE control resonates the
tuned circuits of the signal frequency mixer and
driver stages driving the final amplifier stage.
The control is always tuned for maximum trans-
mitter output when operating as a transmitter or
as a transceiver with the SX-146 receiver.
4-5. CARRIER LEVEL.
The CARRIER LEVEL control sets the RF
output level for CW operation and during the
transmitter tuning process for CW or SSB opera-
tion. The control also functions when the CAL
switch is set at ON to control the calibrate signal
level.
4-6. BAND SELECTOR.
The BAND SELECTOR is an eight position
rotary switch which selects the tuned circuits and
crystals required to tune the frequency ranges
shown on the dial. The color coded panel markings
refer to the USB/LSB coding for the two side
band pOSitions on the OPERATION control.
4-7. FINAL TUNE.
The FINAL TUNE control drives a variable
capacitor that tunes the pi-network used to couple
the PA stage to the antenna load. The control is
calibrated in band segments to permit presetting
the capacitor near resonance during the tuning
procedure.
4-8. METER SWITCH.
The METER switch selects either of two
metered circuits in the transmitter.
1. At MA the meter is used to read the
idle plate current when setting the BIAS ADJ. con-
trol, and to indicate final amplifier stage plate
current on the 40 to 300 milliampere range.
2. At RFO, the meter indicates the RF
voltage across the 50 ohm transmission line at
the output of the transmitter. The scale is cali-
- 7

brated in percent offull scale and the meter serves
to indicate maximum RF power output whentuning
up and
operating the transmitter.
4-9. CALIBRATE SWITCH.
The transmitter provides a low level CW
carrier signal for frequency spotting purposes
when the CAL switch is set at ON. (When operat-
ing in the CW mode, the key must be closed to
obtain the calibrate signal.) The calibrate signal
level may be varied with the CARRIER LEVEL
control if desired. Setting the CAL switch at
ON places the control relay in the transmitter
in the standby position to place the station re-
ceiver in the receive mode to pick up the signal.
4-10. VFO SWITCH.
This two position switch selects the mode of
operation when a Model SX-146 receiver is inter-
connected with the transmitter. If the transmitter
is operated as a single unit the VFO switch is left
in the XMTR position. With the SX-146 receiver
interconnected, the two units may be operated
together as a transceiver (VFO switch at RCVR)
or as separate transmitter and receiver units.
(VFO switch at XMTR). When operating in trans-
ceive mode the receiver VFO tuning also controls
the transmitter frequency.
4-11. DIAL CALIBRATION.
This is a small lever extending through the
panel directly below the center of the dial window.
It moves the dial mechanism to the right or left,
as necessary, to zero out any calibration error
between the dial and pointer.
SECTION V
TUNING PROCEDURE
5-1. GENERAL.
The tuning procedure for the Model HT-46
transmitter is not complicated, however, care
should be exercised in tuning to insure optimum
performance. Tuning (peaking) should be per-
formed on or near the intended operating frequency
on all bands. If the VFO dial of the transmitter or
receiver (when operating in transceive mode) is
tuned an appreciable amount away from the fre-
quency at which the transmitter was previously
tuned, it will be necessary to repeak the DRIVER
TUNE
and FINAL TUNE controls for maximum
output. (Meter switch at RFO). As experience is
gained in the operation of the transmitter on the
various bands, the operator will be able to judge
when
he has tuned far enough to require re-
peaking. In general, the lower frequency bands
require more frequent retuning for the same shift
in frequency on the dial.
The output of the transmitter must always
be connected to a 50 ohm, resistive load such as
a dummy load or suitable antenna havinga 50 ohm
termination at the operating frequency.
5-2. BIAS ADJ.
Before and while operating the transmitter
check and if necessary, set the BIAS ADJ. control
for an idle (no signal) plate current of 40 milli-
amperes. Refer to paragraph 8-3 for detailed
instructions on setting the BIAS ADJ. control.
5-3. BASIC TRANSMITTER TUNE-UP.
Pre-set the following controls as indicated:
8 -
OPERA TION •••••••••••••.•• STBY
MIC GAm ••••.•••••• MIN (Full CCW)
DRIVER TUNE
•.•• Near band segment
CARRIER LEVEL ••••• MIN (Full CCW)
BAND
SELECTOR...... Desired band
FINAL TUNE. • • • . Desired band segment
METER ••..•.•.••••.•• Set at RFO
CAL. • . • • • •• • . • • . • • • • • • • .• OFF
VFO • • • • • • •• . • • . • • • • • • • •• XMTR
TUNING DIAL
••••• Desired frequency
1. Set OPERATION control at CW-TUNE
and close the keyer circuit if a keyer is plugged
into the KEY jack.
2. Turn CARRIER LEVEL control clock-
wise until a small RFO indication is observed
on the meter. On some bands the preliminary
DRIVER TUNE setting may require altering to
obtain a meter reading.
3. Adjust the CARRIER LEVEL control to
hold an RFO meter reading near mid scale and
first tune the FINAL TUNE control for maximum
RFO and then adjust the DRIVER TUNE for maxi-
mum RFO. Always resonate the final amplifier
stage before applying high drive levels to the
stage as may happen when the DRIVER TUNE or
CARRIER LEVEL controls are adjusted.
5-4. CW OPERATION.
1. Tune up the transmitter as outlined in
paragraph 5-3. When a keyer is plugged into the
key jack, its key circuit must be closed to permit
tuning for either CW or SSB operation. If the
transmitter is set up to drive a linear amplifier,
adjust the CARRIER LEVEL control for the drive
level required by the linear amplifier. When op-
erating into an antenna load, advance the CARRIER

LEVEL control to just below saturated drive leve1.
In
either case, repeak the FINAL TUNE and
DRIVER TUNE
controls at this level for maximum
output.
2.
Saturated drive level is determined in
the following manner. Start from the full counter-
clockwise CARRIER LEVEL control setting and
slowly
increase the carrier output level while
observing the RFO meter reading. Set the control
at a point where further rotation does not cause
an appreciable increase inthe RFO meter reading.
This is saturated output. Back off the CARRIER
LEVEL control setting and operate Slightlybelow
this leve1.
3. The
transmitter is now ready to key.
To
reactivate the receiver, set the OPERATION
control at STBY.
5-5. PUSH-TO-TALK SSB OPERATION.
1. Tune the transmitter as outlined in
paragraph 5-3 and paragraph 5-4. Note the RFO
meter reading obtained for maximum drive level
to the linear amplifier or the maximum saturated
output when operating into an antenna load.
2.
Return the CARRIER LEVEL control to
MIN and set the OPERATION control at the USB
or LSB position desired. The customary use ofthe
upper or lower side band changes from band to
band
in the amateur bands.
3.
Depress the microphone push-to-talk
switch, speak into the microphone in a normal
voice level, and advance the MIC GAIN control
until the RFO meter swings upward to approxi-
mately one-half the meter reading noted at maxi-
mum output during tune-up with carrier. The
microphone
gain control setting will be found to
be less critical because ofthe compression action
of the AALC
circuitry; however, the knob setting
still depends upon the type of microphone, the
operator's voice characteristics, and his operating
habits. Sufficient microphone gain has been built
into the Model HT-46 to handle the usual range
of levels associated with communications type
microphones.
4. Releasing the microphone switchbutton
will
return the station to the receive condition.
5-6. VOICE CONTROLLED SSB OPERATION.
The Model HT-46 transmitter with the VOX
control unit Model HA-16 installed will operate
with voice contro1. When the accessory unit is
installed and the station is wired per Figure 3,
the follOwing
operating procedure will apply:
1.
For push-to-talkoperation, setthe PTT-
VOX selector switch of the VOX control unit at
PTT.
2. To set up the VOX control unit, initially
set the PTT- VOX selector switch at PTT, and set
the three controls (SENS., DELAY, and ANTI-
TRIP)
at their full CCW pOSitions. Reduce the
audio gain on the
station receiver to a relatively
low level.
3. Use the tuning
procedure outlined in
paragraphs 5-3, 5-4 and 5-5 to ready the trans-
mitter for SSB operation. With the OPERATION
control on the transmitter set for SSB operation,
set the selector switch on the VOX control unit
at VOX and set the accessory unit controls as
follows:
A. Advance the SENS. control (clock-
wise), while talking into the microphone, until
the
VOX relay closes on the first syllable of
speech. (Use no more VOX gain than necessary
for best results.)
B. Adjust the DE LAY control for the
desired drop-out delay. The delay period shouldbe
long enough to
prevent change-over between words
but not long enough to miss the other operator's
quick reply.
C. Set the receiver audio gain control
for the desired listening level and advance the
ANTI-TRIP
sensitivity control (clockwise) until
the
received signals do not actuate the VOX relay.
Excessive anti-trip gain or a major increase in the
established listening level may lock out the voice
control system.
NOTE
Some microphones equipped for push-
to-talk control have shorting contacts
in the switch to disable the microphone
element when the push button is re-
leased. VOX operation will not be
feasible unless this circuitry is dis-
connected within the microphone.
5-7. TRANSCEIVE (SLAVE) OPERATION.
1. The Model HT -46 transmitter andModel
SX-146 receiver must be inter-connected as shown
in
Figure 3 to perform the transceive function.
2. The INT. OSC/EXT. OSC.
switchonthe
rear apron of the Model SX-146 receiver mustbe
set at INT. OSC. to supply the required signal to
the
transmitter for transceive operation.
- 9

3, Before exact on frequency transceive
operation can be accomplished with the two units,
their carrier oscillator frequencies for upper and
lower sideband operation must be matched within a
few cycles. To synchronize the two oscillators,
remove the top section of the receiver cabinet
and proceed as follows:
follows:
A. Set the receiver controls as follows:
RF GAIN .......... , MAX
AVC . . . . . . . . . • . . . . . .. ON
PRESELECTOR . Peak on signal
from transmitter
SELECTIVITY .. 2.1 or 5.0 (If
operating)
BAND SELECTOR .... " 3.5
AF GAIN • . . . . .. As desired
CAL ................ OFF
ANL . . . . . . . . . • . . . . .. OFF
OPERA TION . . . . . .. Red USB
TUNING DIAL
....... 3.8 MC
B. Set the transmitter controls as
OPERATION ..••... Red USB
MIC GAIN . . . • • . . . . .. MIN
DRIVER TUNE
... Peak on signal
CARRIER LEVEL...... MIN
BAND
SELECTOR ....... 3.5
FINAL TUNE
.•.• Peak on signal
METER ........... Optional
CAL. . . . . . . . . . . . . . . .. ON
VFO. . . . . . . . • . . . . .. RCVR
TUNING DIAL . . . Optional (non-
operating)
C. Adjust the DRIVER TUNE, FINAL
TUNE and CARRiER LEVEL controls on the
transmitter and the PRESELECTOR and tuning
controls on the receiver for maximum "s" meter
reading on the receiver.
D. On some units the frequency differ-
ence between the receiver's 8998.7 KC detector
oscillator and the transmitter's 8998.7 KC carrier
oscillator may be so small that the beat between
them can only be observed on the "S" meter, other
units may be separated enough to hear a beat
note in the receiver. Adjust the CARRIER LEVEL
control on the transmitter for the loudest beat
note or maximum pulsation of the "s" meter
pointer.
E. Adjust the 8998.7 KC BFO trimmer
(C53) on the receiver chassis for zero beat by
watching the "S" meter and setting the trimmer
for the slowest pointer oscillation possible. Do
not reset the carrier oscillator frequency of the
transmitter, its oscillators are matched to the
transmitter's filter. See paragraph 8-14 for the
carrier oscillator adjustment procedure for the
transmitter.
F. Set the OPERATION controls on the
transmitter and receiver to the opposite side band
(Red LSB) and set the 9001.5 KC BFO trimmer
(C60) on the receiver chassis for zero beat as in
step E. The transmitter and receiver are now
matched exactly for frequency of reception, and
transmission when operated in the transceive
mode. The procedure outlined in step 3 need not
be repeated each time transceive operation is
desired, only an occasional check maybe required.
4. With the receiver BFO frequencies set
as outlined in step 3, either separate transmitter
control or transceive operation may be accom-
plished by setting the VFO switch on the trans-
mitter at XMTR for separate control or at RCVR
for transceive control. When operating the two
units as a transceiver, the transmitter tune up
and operating procedure remain unchanged in all
respects except for the tuning control function
which is now controlled by the receiver tuning.
For this reason care should be exercised when
tuning the
receiver outside the American amateur
bands to avoid transmitting on unauthorized
frequencies.
SECTION VI
THEORY OF OPERATION
6-1. GENERAL.
The Model HT-46 utilizes the solid state
modulator followed by selective filter principle of
sideband generation. Single conversion is used to
translate the Signal generation frequency (9000 KC)
to the output frequency. The heterodyning signal
is generated by the VFO directly on the 80 and
20 meter bands and indirectly by pre-mixing with
the heterodyne crystal oscillator for the remaining
bands. For "slave" or transceiver operation with
the Model SX-146, the SX-146 pre-mixed injection
is substituted for the transmitter's pre-mix stages
10 -
and the carrier oscillator frequencies for thetwo
units are matched within cycles to provide equal
receive and transmit frequency.
6-2. SIDEBAND GENERATION.
The carriers for the upper and lower side-
band signals are generated in tube V2B at a nom-
inal frequency of 8998.7 KC and 9001.5KC. These
are the frequencies that fall 25 DB down the skirts
of the 6 pole crystal filter which is centered at
9000 KC. The 8998.7 KC 'carrier, when modulated
by the diode modulator CRI and CR2 produce an

TO VOX
UNIT
HA-16
BAND 8998.7KC 900I.SKC
80M USB LSB
4QM LSB USB
20M USB LSB
15M LSB USB
10M LSB USB
LSB .1USB
= =
J 1
BOM-5.5 TO 5.0MC
4QM-16.0 TO 16.SMC
20M- 5.5 TO 5.0MC
15M- 30.5 TO 30.0MC
tOM- 37.0 TO 39.0MC
80M-3.5 TO 4.0 MC
4OM-7.0 TO 7.5 MC
20M-14.0 TO 14.S MC
ISM-21.0 TO 21.5 Me
IOM-28.0 TO 28.5 MC
IOM-2B.5 TO 29.0 MC
1---If------------1 :g==~~:g +8 ~61M~C
XMTR~ RCVR
SX-146
N FREQUENCIES
ME AS FREQUENCV
SHOWN FOR V4
ABOVE. SX-146
':" INJECTION
33.SMC 32.SMC 2SMC
33MC 32MC 21.SMC
156-006856
Figure 6. Block Diagram of Model HT-46 Transmitter.
upper sideband suppressed carrier signal at 9000
KC. Conversely, the 9001.5KCcarrierwhenmod-
ulated produces a lower sideband signal at 9000
KC. The modulator is driven at audio frequency
by the two triode stages of tube V1 and the cathode
follower triode in tube V2. Audio for the VOX
adapter Model HA-16 is taken from the plate of
the first audio amplifier stage ahead of the MIC
GAIN
control.
The 9000 KC sideband signal is amplified
by tube V3A and coupled to the signal mixer tube
V4 where the information signal is translated to
the operating frequency.
6-3. HETERODYNE SIGNAL GENERATION.
To translate the 9000 KC information signal
to the operating frequency, a heterodyne frequency
signal is generated either within the transmitter
by tubes V7 (VFO) and V8 (Heterodyne Crystal
Oscillator -Mixer) or for "slave" operation it is
taken from the Model SX-146 receiver through the
Heterodyne mixer tube V8B working as an RF
amplifier stage. The plate circuit of the hetero-
dyne mixer tube (V8B) is coupled to the signal
mixer grid through bandpass transformers T2, T3
and T4 on 40M, 15M and 10M and through a broadly
tuned 5 MC-5.5 MC tuned circuit L25 and R58 on
80M and 20M in order to accommodate the tuning
range of the VFO.
The desired mixer product resulting from
the 9000 KC information signal and the tunable
heterodyne CW signal at the signal mixer grid is
now amplified by the driver stage tube V5 and the
power amplifier stage tube V6. The amplified sig-
nal is coupled to the antenna transmission line
with a pi-network that is pre-adjusted to properly
load the final amplifier tubewhena 50 ohm antenna
load is connected to the transmitter. The mixer and
driver stage coils are gang tuned on each band by
the two section capacitor C40A and C40B (DRIVER
TUNE). The
final stage pi-network is tuned on the
input side by capacitor C67 (FINAL TUNE).
6-4. AALC (AMPLIFIED AUTOMATIC
LEVEL CONTROL).
To protect the final amplifier stage from ex-
cessive "flat-topping" during SSB transmissions
an Amplified Automatic Level Control (AALC)
system is placed in operation in the following
manner. When a small amount of grid current is
developed in the final stage, a small ripple volt-
age at audio frequency is developed on the ampli-
fier grid bias line in proportion to the amount of
grid current developed by the over driven con-
dition. This audio signal, which is not present at
below grid current levels, is amplified by the
triode section of tube V3B and rectified by diodes
CR3 and CR4. The resulting DC voltage is then
fed to the grid return of the 9000 KC IF amulifier
tube V3A as a gain control grid bias. •
6-5. METER CIRCUIT.
The metering circuits of the Model HT -46
transmitter are designed to provide an accurate
means of determining the idle and operating plate
current of the final amplifier tube and to monitor
the RF voltage appearing across the output ter-
minals of the transmitter for optimum tuning of
the final and driving stages.
-11

Since most milliameter calibration accuracy
leaves much to be desired in the first third of
the scale, a bridge circuit (R40, R41, R43 and R44)
is used in the HT -46 which sets idle plate current
at a zero meter current condition, hence the 40
milliampere calibration mark appears at theindex
point
of the meter. When the final tube is driven
to higher than 40 milliamperes of plate current,
the meter circuit automatically causes the meter
to swing up accordingly.
The METER switch
S4 transfers the meter
between the bridge circuit for plate current mea-
surements andthe diode load circuit for measuring
RF voltage at the output of the transmitter. The
RF voltage at the output of the transmitter is
divided down by resistors R46 and R47 to a level
which can be handled by the rectifier diode CR5.
The
resulting DC voltage is then metered by the
DC milliameter on a percentage basis for tuning
purposes.
6-6. VOX ACCESSORY CIRCUIT.
The VOX Control Unit Model HA-16 is an
accessory item which will add voice control tothe
Model HT-46 transmitter for ssa operation.
The
VOX adapter takes its power and cir-
cuit wiring from the Model HT-46throughthe VOX
UNIT connector on the transmitter. The VOX unit
samples audio from the transmitter and amplifies
the signal with tubes V401A and V402A. It also
samples the audio signal at the speaker of the
receiver and amplifies this signal withtube V403.
Normally the speaker outputpickedupbythe
microphone would
cause the control relay to close,
placing the transmitter on the air, butby properly
setting the VOX sensitivity and ANTI-TRIP gain
controls, the two signal levels in the VOX circuit
may be matched so that the rectified DC voltages
controlling the relay tube V401B cancel and hold
the
transmitter off the air.
When the operator speaks into the micro-
phone the balance is upset. The audio signal from
the transmitter overcomes the anti-trip signal
from the receiver and the control relay turns the
transmitter on.
To avoid having the control
relay switch on
and off between
words while the operator is talk-
ing, a delay circuit consisting of the DELAY
control R411 and
capacitor C405 sets the time
lapse between the last spoken wordandthe change
over from transmit to receive.
SECTION VII
SERVICE DATA
7-1. SERVICE OR OPERATING QUESTIONS.
For further information regarding operation
or servicing of this unit, contact the dealer from
whom it was purchased. The Hallicrafters
Company maintains an extensive system of
Authorized Service Centers where any required
service will be performed promptly andefficiently
at no charge if this equipment is delivered to the
service center within 90 days from date of pur-
chase by the original buyer and the defect falls
within the terms of the Warranty. It is necessary
to present the bill of sale in order to establish
warranty status. After the expiration of the
warranty, repairs will be made for a nominal
charge. All Hallicrafters authorized service cen-
ters display the sign shown below. For the one
nearest you, consult your dealer or your local
telephone directory.
12 -
Make no service shipments to the factory
unless instructed to do so by letter, as the Halli-
crafters Company will not accept responsibility
for unauthorized shipments.
The Hallicrafters Company reserves the
privilege ofmaking revisions in current production
and
assumes no obligation to incorporate such
revisions in earlier models.
7-2. CABINET REMOVAL.
Access to tubes, dial lamps, crystals and
most adjustments may be had by removing the
top portion of the cabinet only. This
is done by
removing
three Phillips type screws on each side
of the cover and lifting the cover straight up.
The bottom
portion of the cabinet may be
removed only after the top portion has been re-
moved. To remove the bottom cover unit, turn
the set upside down. Remove seven Phillips type
screws and lift bottom clear.
7-3. DIAL CORD RESTRINGING.
Remove the cabinet top cover (refer to
paragraph 7-2). Follow the arrow and lettered
sequence in Figure 7. Maintain a spring expan-
sion of 1/4-inch to 1/2-inch on the dial cord

H
THIS STRING SEGMENT LI ES
ON PULLEY IN FRONT OF
STRING SEGMENT C-B.
VFO CAPACITOR AT
MAXIMUM CAPACITY
E
3112 TURNS
USE
50 POUND TEST DACRON CORD
OR EQUIVALENT.
156-007041 B
Figure 7. Dial Cord Restringing Diagram.
spring. After completing the stringing operation,
place the pointer on the rail and engage the dial
cord with the pointer clips. The pointer should
be adjusted to just miss the nylon pulleys at the
two
extremes of its travel. After the pointer is
adjusted, apply a drop of rubber cement to the
dial cord and the pointer clip to hold the clip in
place.
7-4. TROUBLE SHOOTING.
In the design of this transmitter, full con-
sideration was givento keepmaintenance problems
at an absolute minimum. As in all well-designed
electronic eqUipment, maintenance and repair
problems are generally confined to the checking
and replacement of tubes and semi-conductor
devices which may become defective. Malfunctions
of
this nature are usually easily isolated and
corrected. However, it is entirely possible that
a more obscure malfunction may arise. In this
event, only thoroughly trained technical personnel
should attempt to service equipment of this com-
plexity.
A
recommended aid to trouble shooting the
Model HT-46
transmitter is a general coverage
receiver which can be used to provide a quick
check on the various oscillator circuits withinthe
HT-46. A
lead connected to the antenna of this
receiver, when placed in the proximity of the
oscillator tube in the circuit to be checked, can
determine the presence or absence of a signal
from the stage in question.
If a malfunction occurs when operating on one
particular band and/or mode of operation, the unit
should
be checked on all other bands and in all
other modes of operation to isolate the difficulty.
A
careful study of the block diagram (Figure 6)
will give a quick clue as to which tubes should be
checked. The voltage
chart and resistance chart
(Figures 10 and 11) and schematic diagrams
(Figures 14 and 15) will also aid in isolating and
correcting a malfunction.
SECTION VIII
ALIGNMENT PROCEDURE
8-1. GENERAL.
The Model HT -46 Transmitter has been
accurately aligned and calibrated at the factory
and, with normal usage, will not require realign-
ment for extended periOds of time. Service or
replacement of a major component or circuit
may require subsequent alignment, but under no
circumstances should realignment be attempted
unless the malfunction has been analyzed and
definitely
traced to mis-alignment. Alignment
should only be
performed by persons experienced
in this field, using the proper test equipment.
NOTE
Do not make adjustments unless the
operation of the transmitter is fully
understood and adequate test eqUipment
is available. Refer to figures 8 and 9,
the top and bottom views of the
trans-
mitter, for the location of all adjust-
ments.
- 13

L7 L5 L4
L10 --+--==::~::iii~-t~
V6
6HF5-
CI04
CI03
V9
OA2
14 -
T5
CI02 L26 LI RI3 TI
CI7
Figu re 8. Model HT·46, Top View.
T2 T3 T4
CI4
L23
L3
)'8
Y7
D5-1
c-1..!---- Y6
-!-!-_--Y5
-!-!-_--Y4
~!----Y3
V7
-6BA6
_ V3
:L--!-;--- 6EA8
...!-~---C82
-4-5---- L24
---rr---- L2
C83
D5-2
FL-I
MI
CI3
156·0069596

8-2. EQUIPMENT REQUIRED.
1. RF Signal Generator; Hewlett-Packard
Model 606A or an equivalent signal generator
having up to one volt output at an impedance of
70 ohms or less and a frequency range to 40 MC.
2. A Vacuum Tube Voltmeter (VTVM);
Hewlett-Packard Mode1410B, or equivalentVTVM
having an RF probe good to 40 MC.
3. A dummy load;
50 ohms non-reactive,
rated at 100 watts. Bird Wattmeter or equivalent.
The
load may be made up of carbon resistors
totaling 100 watts dissipation.
4. AF Signal
Generator; Hewlett-Packard
Model 200 AB, or equivalent.
5. AF Voltmeter; Ballentine Model 300 or
equivalent, capable of measuring 1 to 5 millivolt
level. 6. A
general coverage or amateur band
coverage reeeiver' With 100 KC crystal calibrator.
8-3. BIAS ADJUSTMENT.
The final amplifier bias must be set before
any extensive checks are made on the transmitter.
Properly setting the bias will insure normal
operating plate dissipation for the tubes in the
final
amplifier and driver stages. Adjustthe BIAS
ADJ. control located on the rear chassis apron as
follows:
1. Set theOPERATION contro1atSTBYand
allow at least ten minutes for the unit to warm
up. Note that the meter pointer swings to the left
of its normal rest position withthe METERswitch
at MA and returns to its rest position with the
switch set at RFO. Set the METER switch at MA
and the MIC GAIN control full CCW.
2. Set the OPERATION control at one of
the two USB/LSB positions, press the microphone
switch to place the transmitter in operation, and
set the BIAS ADJ. control for 40 milliamperes.
Release the microphone switch and note that the
meter pointer swings to the left against its mech-
anical stop. If the microphone switch does not
place the transmitter in operation check to see
that the jumper plug is in the VOX UNIT connector
on the
rear chassis apron.
NOTE
If the VOX Control Unit Model HA-16
has been installed. Set the PTT-VOX
switch at PTT.
3. Set the METERswitch at RFO and press
the microphone switch. The meter pointer should
remain at rest. If it indicates RF output, reset
the carrier balance adjustment per paragraph 8-4
and repeat the bias adjustment procedure.
NOTE
The idle plate current may rise to 50
or 60 milliamperes after an extended
transmission period. This is normal
and it will return to 40 milliamperes
after a cooling off period. A rising
plate current may indicate that the idle
plate current was set up too soon after
turning on the transmitter; correct by
setting the BIAS ADJ. control as out-
lined above.
8-4. CARRIER BALANCE.
Adjust the carrier balance controls as
follows:
1. The transmitter should be allowed to
reach operating temperature before making the
carrier balance adjustments. Remove the cabinet
cover from the transmitter as described in para-
graph 7-2. With the chassis resting on the table,
right side up, and connected to a dummy load or
antenna load, tune the unit for SSB operation.
(Refer to paragraph 5-5.)
2.
Turn the MIC GAIN control fully counter-
clockwise to remove all audio from the modulator
stage. With the OPERATION control set at either
of the USB/LSB positions, close the microphone
switch and adjust the CARRIERBALANCE controls
(capacitor C17 and potentiometer R13) for mini-
mum RFO voltage. (Meter switch at RFO.) With
an antenna or dummy load connected to the trans-
mitter, the meter will drop to zero near the nUll.
Release the microphone switch.
3. Disconnect the antenna
load and again
close the microphone switchand repeat thebalance
adjustment. The meter will still drop to zero, but
will be more sensitive with the load removed.
Take care not to feed excessive carrier through
the system with the load removed.
4. A more exactingbalance can be obtained
by tuning a receiver, having an "S" meter, to the
transmitter frequency. Adjustthe CARRIER BAL-
ANCE
controls for minimum "S" meter reading
and
then switch the OPERATION control to the
opposite sideband and check the "S"
meter read-
ing. If it increased, touch up the balance controls,
switching between USB and LSB until bothsideband
carrier frequencies produce equal "S" meter
readings. If the selectivity of the receiver is
sharp, it may be necessary to retune the receiver
slightly since the two carrier oscillators are
approximately 2.8 KC apart.
- 15

R65 R66 R68 CR7 THRU CRI4 CR5 CRG RG7 CI05 CI9 RI3 R72 CIO Y2 CI2 YI
FI
J2
R70-----r-
J5-----
R71
J4 ------''II
J3------''1l
S2H LII S2G S2F L9 L10
Ll3L12 S2E L6
S2D S2C L23 S28 S2A
Figure 9. Moclel HT-46, Bottom View.
16 -
156-0069608

8-5. FINAL AMPLIFIER NEUTRALIZATION.
1. Neutralization check. With the Model
HT-46 transmitter in its cabinet (all hardware in
place) and connected to a dummy load, tune the
transmitter at 2S,750 KC in the CW mode as
described in paragraphs 5-3 and 5-4. Adjust the
CARRIER LEVEL control for 50 volts RMS output
(approximately 50% on the RFO meter if an RF
voltmeter is not available). Carefully tune the
FINAL TUNE control through resonance and ob-
serve the plate current dip and output voltage
maximum. If both occur at the same setting, the
amplifier is neutralized. Neutralization may be
checked on 15M, 20M, 40M and SOM by switching
bands and tuning up at the same VFO dial setting.
2. Neutralizing the Model HT-46. If the
check outlined above indicates a need for neu-
tralization, remove the cabinet cover to adjust the
neutralizing capacitor C62. Proceed as outlined
for the neutralization check and adjust neutraliz-
ing capacitor C62 in 1/2 turn or 1/4 turn steps
until the plate current dip and output voltage
maximum coincide at the center of the 10M band
and remain in close agreement at the 2S,000 KC
and 29,700 KC band edges. The cabinet cover does
not have to be in place for the test, however the
final amplifier compartment cover and the cabinet
bottom plate must be in place.
CAUTION
HIGH VOLTAGE APPEARS ON THE
ADJUSTMENT SCREW OF THE NEU-
TRALIZING CAPACITOR AT ALL SET-
TINGS OF THE O:PERATIONCONTROL
EXCEPT OFF.
NOTE
When neutralization is required and the
heterodyne crystal oscillator crystals
for the 2S.0 and 29.5 band segments of
the 10 meter band are not available,
the neutralization procedure may be
carried out on the 15 meter band. Neu-
tralization should be checked at 21,000
KC
and 21,500 KC for equal run out on
this band.
8-6. VFO MECHANICAL INDEX.
With the dial reset lever centered in its
panel slot, the pointer over travel at each end of
the dial should be equal and the pointer should not
engage the nylon pulleys at the extremes oftravel.
8-7. VFO CALIBRATION ALIGNMENT.
The frequency range of the VFO, over the
calibrated portion of the dial, is 5.0 MC to 5.5 MC.
The VFO frequency may be picked up on a general
coverage receiver or the VFO frequency may be
translated to the SOM band by operating the trans-
mitter in CW mode, and the SOM signal picked up
on an amateur band coverage receiver. The re-
ceiver should have an accurate 100 KC crystal
calibrator to check the dial calibration at every
100 KC point across the dial of the transmitter.
1. Trimmer adjustment only. A trimmer
capacity correction is indicated if the dial cali-
bration check across the dial, at the 100 KC
check points, consistently falls to one side of the
pointer and cannot be corrected by the dial reset
lever. Recalibrate the VFO as follows:
A. Set the dial reset lever at the center
of its slot.
B. Set the dial at 3500 KC (5500 KC
VFO
frequency) and tune up the transmitter in
CW mode (OPERATION control at CW-TUNE, VFO
switch at XMTR) on the SOM band. With the CAR-
RIER LEVEL control set full CCW enough SOM
Signal will be present to be heard in the amateur
band receiver.
C. With a general coverage receiver
tuned to 5500 KC, or an amateur band coverage
receiver tuned to 3500 KC, adjust VFO trimmer
CS2 for zero beat with the 100 KC calibrator
in the receiver.
D. Check across the dial at the 100
KC
check pOints. If the frequency error is less
than approximately 3 KC, the calibration is within
acceptable limits. If the error increases and
exceeds 3 KC at the high frequency end of the
dial (VFO = 5000 KC), the VFO will require a
coil adjustment in addition to the trimmer adjust-
ment.
2. Trimmer and coil adjustments. If the
check carried out in step Dabove indicates a need
for both trimmer and coil adjustment, proceed
as follows:
A.
Set the dial at 4000 KC (VFO =
5000 KC), tune up in CW mode on the SOM band
and adjust eoil L24 for zero beat with the 100 KC
calibrator in the receiver.
B. Repeat the trimmer adjustment at
3500 KC (VFO = 5500 KC) and the coil adjustment
at 4000 KC (VFO = 5000 KC) until the two dial
settings are exactly on frequency.
C. Check the calibration across the
dial at the 100 KC pOints. If the frequency error
is less than one pointer width, the calibration is
within acceptable limits. If the error is in excess
of one pointer width at any of the mid points,
with the end limits on frequency, the VFO capa-
citor C 83 should be "knifed" . This operation
should not be attempted by other than qualified
personnel, thoroughly familiar with the technique.
- 17

8-8. HETERODYNE CRYSTAL OSCILLATOR
ALIGNMENT.
Bsfore changing the core setting of coil L23,
check the injection voltage between test point B
and chassis. The following procedure should be
used to check and adjust the heterodyne crystal
oscillator.
1. Remove the VFO tube V7 to disable
the VFO injection.
2. Set the OPERATION control at CW-
TUNE, CAL
switch at OFF and VFO switch at
XMTR.
3.
Connect the VTVM probe to the grid
(Pin 2) of heterodyne mixer tube VBB (Test point
B) and ground clip to chassis.
4. Rotate the BAND SELECTOR control
through all positions and note the RMS AC injec-
tion voltages obtained. Normal injection voltages
are as follows:
3.5
7.0
14.0
21.0
*2B.0
2B.5
*29.0
*29.5
Zero
0.9V to 1.4V
Zero
0.6V to O.BV
O.BV to 1.0V
0.9V to
1.1V
0.6V to 0.9V
O.BV to 1.1V
*NOTE
These bands will have zero injection
voltage if crystals Y3, Y4 and Y6 have
not been plugged into the transmitter.
5. If adjustment is required, set the BAND
SELECTOR control at 29.5, the highestfrequency
segment of 10M. (If crystal Y6 has not been
added set the band selector at 2B.5.) Adjust core
of coil L23 for approximately 90% of maximum
injection voltage on the gentle slope side of
resonance. Switch through the bands and check
injection. A small touch up on the core will yield
the injection pattern shown in step 4. Replace VFO
tube V7.
8-9. HETERODYNE MIXER BAND-PASS
TRANSFORMER ALIGNMENT.
Adjustment of transformers T2, T3 and
T4 should
not be attempted unless the injection
voltage varies more than 30% at test point C
when
the VFO is tuned across the amateur band
or the transformers have been replaced and re-
quire complete alignment. Bandpass transformers
are not used for the BOM and 20M bands and no
adjustment on these bands is required.
18 -
1. To check injection or make minor ad-
justments on the bandpass transformers T2, T3
or T4 proceed as follows:
A.
Set CARRIER LEVEL control full
CCW, VFO
switch at XMTR, CAL switch at OFF
and set OPERATION control at CW-TUNE.
B.
Connect VTVM probe to Pin 1 of
tube V4 (test point C) and ground clip to the
chassis.
C. Set BAND SELECTOR at 7.0 to
check transformer T2; 21.0 for transformer T3;
and 2B.0, 2B.5, 29.0 and 29.5 to check trans-
former T4. For this method of checking trans-
former T4 over the complete 10M band it will
be necessary to have crystals Y3, Y4 and Y6
installed and the heterodyne crystal oscillator
aligned per paragraph B-B.
D. Tune the VFO across the amateur
band and observe the variation in injection voltage.
If the variation is less than 30% the transformer
is OK. In general, the injection voltage on BOM,
40M, 20M, and 15M bands will run between 0.3V
RMS
and 0.5V RMS. The 10M band injection will
run between 0.7V RMS to slightly over 1.0V RMS
(No 9 MC signal injection present).
E. If the difference in injection voltage
over the band exceeds 30%, set the VFO dial for
the lowest injection voltage. To avoid upsetting
the band pass response completely, move the
cores in very small increments, noting the direc-
tion and degree of rotation. Adjust only the core
that increases the injection voltage and set it for
approximately 1/2 the variation in injection volt-
age. Again tune the VFO across the band and
evaluate the variation in injection voltage before
touching the cores again. Repeat the procedure
until the injection voltage level is uniform across
the band.
On the 10M band a check on all four
segments is required to evaluate a core adjust-
ment rather than just looking at the variation in
injection across only one segment of the 10M
band.
2.
If a new transformer is installed or a
major transformer adjustment is required, the use
of a signal generator for alignment is recom-
mended. Alignment of the bandpass transformer
with the use of a signal generator is as follows:
A. Connect
the signal generator to the
SX-146 INJECT connector at the rear apron of
the transmitter.
B. Connect the VTVM probe to Pin 1
of tube V4 (test point C) and ground clip to the
chassis.