Hallicrafters SX-42 User manual

Hallicrafters SX-42 Operating Instructions
Excerpted from SX-42 Owner's Manual, Copyright 1946 Hallicrafters Co.
1. GENERAL
The Model SX-42 is a 15 tube superheterodyne radio receiver designed to provide amplitude modulated (a-
m) reception over the frequency range 540 kc (kilocycles) to 110 mc (megacycles) and high fidelity,
frequency modulated (f-m) reception over the frequency range 27 to 110 mc. Calibrated bandspread is
provided for the 80, 40, 20, 10, and 6 meter amateur bands. The general coverage dial and bandspread dial
are operated from one tuning control which consists of two independent knobs turning on concentric shafts.
A dial lock is provided to lock the unused dial while tuning the receiver. This exclusive Hallicrafters feature
insures accurate tuning and logging.
Frequency Coverage
Band
Coverage
Type of reception
1
540-1620 kilocycles
AM/CW
2
1.62-5 megacycles
AM/CW
3
5-15 megacycles
AM/CW
4
15-30 megacycles
AM/CW
5
27-55 megacycles
AM/FM/CW
6
55-110 megacycles
AM/FM/CW
Adequate overlap is provided at ends of all bands. The receiver as normally supplied is designed to operate
from a 105 to 125 volts 50/60 cycle, single phase source of a-c power. These operating instructions also
cover Universal Models which operate from a 105 to 250 volts, 25/60 cycle single phase a-c source.
2. AC OPERATION
Be sure line voltage is 105 to 125 volts and frequency is 50 to 60 cycles before inserting power cord plug
into power outlet. Be sure all tubes are securely inserted in their proper sockets before receiver power is
turned on. The chart below lists the current and voltage data.
Power Consumption
110 Watts
Frequency
50/60 Cycles
Line Voltage
117 Volts
Line Current
0.93 Amperes

During a-c operation, the shorting plug supplied with the receiver must be in the octal socket on the rear
apron of the chassis.
3. D-C OPERATION
The receiver may be operated from a 6 volt d-c source, generally a storage battery, and a 270 volt d-c supply
in the form of "B" batteries or vibrator type power pack. Consult the chart on power requirements at the end
of this paragraph and provide battery or power pack facilities capable of supplying these demands. The
receiver is connected to the--d-c supply as follows:
1. Remove the octal shorting plug for a-c operation from the socket SO-1 located on the rear apron of the
receiver chassis.
2. Wire an octal plug, as shown in Fig. 10, and plug it into socket SO-l. Use #19 (AWG) wire leads for the
270 volt "B" supply connections to pins #3 and #5, and #'12 (AWG) wire leads for the 6 volt battery
connections to pins #1, #7, and #8. CAUTION: Check the wiring carefully before connecting to the battery
supply. The chart below lists the current voltage data.
"B" Voltage
270 Volts
"B" Current
150 ma.
Filament Voltage
6 Volts
Filament Current
5 Amperes
Total battery drain when operating from a 6-volt vibrator power supply is approximately 16 amperes.
4. OUTPUT CONNECTIONS
Output connections for the speaker are provided for on the rear apron of the chassis. Two output impedances
are available. Either the 500/600 or the 5000 ohm speaker connection may be used according to the output
impedance desired. This arrangement of dual output impedances will accommodate most requirements. The
Hallicrafters Model PM-23 speaker requires 5000 ohms impedance; the Hallicrafters Model R-42, R-44, R-
75, or R-80 requires 500/600 ohms. However, any standard type, permanent magnet dynamic speaker with
output transformer may be connected to the output terminals. If the permanent magnet dynamic speaker
impedance is unknown, try the 5000 ohm and then the 500/600 ohm impedance, and use the one which gives
the better tone quality and: volume.
5. PHONO INPUT CONNECTION
A receptacle is provided on the rear apron of the chassis for connecting a phonograph record player to the
receiver. This receptacle is designed to accommodate a Cinch, type M-93, pin connector plug.
6. ANTENNA AND GROUND CONNECTIONS
The Model SX-42 is designed for a 300 ohm antenna impedance. The antenna impedance is not critical and
excellent reception can be obtained from an antenna of from 50 to 600 ohm impedance. For maximum
performance, the best possible antenna should be employed.
The antenna terminals on the Model SX-42 are arranged for any type of antenna from those requiring a
ground to those using a transmission line. The transmission type of antenna connects to the A-1 and A-2
terminals whereas a single wire antenna utilizes terminal A-1 for the antenna lead. A-2 and GND terminals
must be connected together and connected to a good ground.

7. DETAILED OPERATIONS
a. Controls and Their Functions. In order to obtain the desired results from the receiver, it is recommended
that you become familiar with the function of each control, Red indicators on the controls for broadcast
reception and green for f-m reception are there to simplify operation. Controls and their functions are as
follows:
(1) BAND SELECTOR. The BAND SELECTOR knob operates the bandswitch to select the desired band of
frequencies. The frequency range covered by each band is read directly on the BAND SELECTOR knob.
(2) General Coverage Tuning and Bandspread Tuning Control. The larger of the two concentric knobs tunes
the receiver to the desired frequency. The smaller knob provides bandspread action or fine tuning as
indicated on the bandspread scale. The winged knob in the center alternately locks the general coverage and
the bandspread dials so that one remains fixed while the other one is being tuned. The knob should be
rotated in a clockwise direction only, locking first one dial and then the other as it is turned through one
complete revolution. Note that the locked dial knob is free to turn, but that the dial itself is locked in
position.
(a) General Coverage Dial. The general coverage dial has six calibrated scales and a logging scale. All six
scales are calibrated in mc. The calibrated metal skirt of the general coverage dial knob acts as the vernier
calibration for the logging scale. The outer logging scale (on the general coverage dial) isdivided into 21
divisions, each division representing one revolution of the vernier dial which also carries a logging scale
divided into 100 divisions, thus providing 2100 divisions for logging use. The dial settings for the various
amateur bands are indicated on the main tuning dial by black dots and the abbreviations 80M, 40M, etc.
directly below the dot. When tuning the amateur bands with the calibrated bandspread dial, the general
coverage dial must be set and locked at the setting corresponding to the amateur band desired.
For a reference when tuning in foreign broadcast stations, the word FOREIGN has been placed at the
appropriate positions along the dial scales. The f-m channel 88 to 108 mc has been divided into 100
divisions by the scale above it marked 0, 10, 20, 30, etc. in green numbers which correspond with the
frequency modulated channel assignments. Since the general coverage and bandspread tuning systems are
electrically related, it is necessary to set the bandspread dial at "0" when tuning the receiver with the
genera1 coverage dial control to obtain correct receiver frequency readings on the general coverage dial.
(b) Bandspread Dial. The bandspread dial has five scales calibrated for the amateur bands and a 100
division logging scale. The five scales are calibrated to read receiver frequency directly in mc when the
general coverage dial has been set to the corresponding indexing dot and locked in position.
(3) AVC-OFF Switch. This switch when set at AVC, provides a relatively constant volume level at the
speaker for reasonable variations in signal strength at the antenna by automatically controlling the sensitivity
of the receiver. Best results are obtained when the SENSITIVITY control is set at maximum sensitivity. The
AVC switch MUST be set at OFF for c-w code reception.
(4) NOISE-LIMITER-ON Switch. This switch opens or closes the noise limiter circuit and is to be set at ON
when the operator wishes to limit excessive noise resulting from automobile ignition and other forms of
noise interference.
The noise limiter circuit "clips" the intermittent noise peaks down to the level of the desired signal where
they tend to become unnoticeable.
(5) RECEIVER-STANDBY Switch. When set at STANDBY, this switch renders the receiver inoperative,
while transmitting or for any other purpose, although the tube heaters remain hot and ready for instant use.
(6) CRYSTAL PHASING Control. This control permits the discrimination of code signals whose frequencies
are very nearly the same. The SELECTIVITY control must be set at one of its three crystal selectivity

positions when using the phasing control.
It is extremely simple to attain single signal c-w reception with the SX-42. First. set the RECEPTION switch
at CW and the SELECTIVITY control at CRYSTAL SHARP. Pick a good solid c-w signal, preferably a
commercial station because a commercial is likely to stay on long enough for you to complete the phasing
adjustment for single signal reception.
You will find on tuning across this signal that it has two amplitudes. Tune first to the weaker of these two
amplitudes. Next, turn the CRYSTAL PHASING control until the weaker of the two amplitudes is reduced
to a minimum. Then, tune to the stronger of the two amplitudes and adjust the PITCH control to a tone most
pleasing to you. This adjustment for single signal selectivity will hold with no further adjustment unless you
change the phasing control.
(7) SELECTIVITY Control. This control determines the sharpness of the response. Six degrees of selectivity
are provided, ranging from CRYSTAL SHARP for c-w code reception under difficult receiving conditions
to NORMAL BROAD response for high fidelity reception.
1. BROAD I-F (for high fidelity reception)
2. MEDium I-F (more selectivity, less bass)
3. SHARP I-F (reduces adjacent channel interferences and gives less highs)
4. CRYSTAL BROAD (similar to sharp i-f but sharper cutting on sidebands)
5. CRYSTAL MEDIUM (greatly increased sideband cutting very little highs present)
6. CRYSTAL SHARP (position of extreme selectivity - practically no sideband content)
(8) TONE Control. This control selects the tone qualities desired by the operator. The four types of response
available are LOW, MED, HI FI, and BASS.
(a) LOW. The bass and high audio frequencies are attenuated to provide a minimum response for voice
reception when the background noise level is objectionably high.
(b) MED. The bass and high frequencies are attenuated somewhat less than for the LOW position providing
a response for more than the ordinary voice frequencies. This position is preferred for voice communication
when the signal to noise ratio will permit.
(c) HI FI (High Fidelity). The bass and high frequencies are passed at the same level as the mid-frequency
range thereby providing as near a true reproduction of the original signal as possible. The response is
essentially flat between 50 and 15,000 cycles per second for high fidelity reception.
(d) BASS. The response in the high frequency end of the audio range remains uniform as for the HI FI
position; however, the level of the lower frequencies is boosted above the level of the medium and high
frequency ranges.
(9) CW PITCH Control. This control varies the frequency of the beat frequency oscillator thus varying the
pitch of the c-w code signal as desired.
(10) SENSITIVITY Control. This control adjusts the sensitivity by varying the resistance in the cathodes of
the r-f and i-f amplifiers. Turning the control to the right increases the sensitivity. This control must be set at
maximum sensitivity when using the carrier level meter. At any other setting of this control, readings of the
carrier meter are meaningless.
8. "S" METER ADJUSTMENT
Adjustment of the "S" meter control is performed by varying the knurled knob located on the rear apron of
the receiver chassis. This control enables you to properly set the "S" meter to zero. In order to make the
adjustment correctly, advance the SENSITIVITY control to 10 (red dot). Set the AVC switch at ON

position. Short the two antenna terminals to the ground terminal and tune receiver off station. Then adjust
the "S" meter control until the pointer rests on left hand zero. Remove the short from the antenna terminals
and the meter will indicate the relative carrier strength of each incoming signal as various signals are tuned
in.
©1995-2010 Philip I. Nelson, all rights reserved