Hallicrafters SX-100 MARK IA User manual

Fig. 1. Hallicrafters SX-1 00 Receiver
SECTION 1.
GENERAL
Your new Hallicrafters SX-100 Selectable Sideband Receiver is precision built to bring you the finest in world-
wide radio reception. This fourteen-tube dual conversion superheterodyne receiver tunes from 538 to 1580 kilocycles and
1. 72 to 34 megacycles, with calibrated electrical bandspread provided on the 80, 40, 20, 15 , and 11-10 meter amateur
bands. You'll hear foreign and domestic shortwave broadcasts, amateurs, police , aircraft, ships-at- sea, and countless
other exciting distant stations . . . as well as all your favorite programs on standard broadcast . The receiver provides
for the reception of CW, AM, and single- sideband signals over its entire tuning range, the upper or lower sideband be-
ing readily selectable by means of a front panel control. This selectable sideband feature not only greatly simplifies
tuning of signal-sideband signals but is also useful in eliminating heterodyne interference when receiving AM signals.
Unlike the ordinary dual-conversion receiver, your SX-100 receiver employs dual conversion on all bands . .<\s
a result, images are practically non-existent. "Razor-sharp" selectivity is made possible by the use of an adjustable
50. 5 kc second IF with four high-Q, permeability-tuned circuits. Receiver selectivity is variable in five steps from
500 cycles to 5 kc at 6 db down and from 5 to 20 kc at 60 db down.
Atuned r-f stage assures maximum sensitivity and a high signal-to-noise ratio for outstanding reception of weak
and
distant signals. A manual sensitivity control prevents overloading by strong signals . An antenna trimmer , adjust-
able from the front panel, permits peaking of the r-f stage to compensate for loading effects of various antennas. A
notch filter circuit allows rejection of an extremely narrow portion of the IF passband. With the notch filter, an inter-
fering signal can easily be "notched out". The position and the degree of notch rejection are adjustable from the front
panel.
Outstanding frequency stability is achieved by the use of ceramic trimmers and coil forms in the 1st conversion
oscillator, extensive temperature compensation, voltage regulation of all oscillators, and the use of a crystal- controlled
2nd conversion oscillator .
Tuning is accomplished by a precIsIOn gear drive tuning mechanism to insure extremely close calibration and
accurate resetability. Smooth flywheel tuning affords maximum traverse speed and operating ease. A 100 division
logging scale on the MAIN TUNING ahd BANDSPREAD knobs, plus a hundredths scale on the tuning dial s, assures ease
and accuracy in loggingand relocating stations of special interest. The logging number is the logging number of the dial
plus tl).e number on the knob scale. For example; if the main tuning dial logging scale reads 12, and the MAIN TUNING
knob scale reads 25, the logging number is 1225. A built- in 100 kc crystal calibrator provides marker signals at every
100 kc on the dial for checking calibration accuracy. A trimmer capacitor , accessible from the top of the chaSSiS,
p ' ~rmi ts adjustment of the calibrating oscillator to exactly 100 kc by comparision with the frequencies transmitted by
station WWV.
An automatic series noise limiter circuit, controlled by a switch on the front panel, reduces interference from
electrical equipment, ignition noise , and other forms of pulse type noise.
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An "S" meter is used when receiving AM signals to indicate the accuracy of tuning and the relative strength of
received signals. The meter is calibrated in microvolts, "s" units from 1 to 9, and in decibels above S9 to + 80 db.
The Receive-Standby switch on the front panel silences the receiver but leaves the heater and plate power on to
provide instant reception between transmission periods. Provision has also been made in the receiver for remote
receive-standby control, and for transmitter switching from the front panel.
Audio output connectionsinclude terminals for a 3. 2-ohm speaker and a 500/600-ohm output for line or speaker.
A front panel jack for headphones is also provided and the speaker is automatically silenced when the headphoneplug
is inserted. A phono input jack at the rear of the receiver permits attachment of a record player.
The receiver is designed to operate on 105 to 125 volt, 50/60 cycle AC current. Provision is also made in the
receiver for operation from an external DC power supply or batteries in areas where AC power is not available.
SECTION 2.
INSTALLATION
2-1. UNPACKING
After unpacking the receiver, examine it closely for damage which may have occured in transit. Should any
Signof damage be apparent, file a claim immediately with the carrier stating the extent of damage. Carefully check all
shipping labels and tags for instructions before removing or destroying them.
2-2. LOCATION
The receiver may be placed in any location that will permit free air circulation through the ventilation holes
and openings in the cabinet. Avoid excessively warm locations such as those near radiators and heating vents. The
external speaker may be located in any convenient pOSition although it is recommended that it not be placed on top of
the receiver for reasons of ventilation.
2-3. ANTEN NAS
The r-f inputof the receiver is designed for operation form either a single-wire antenna, or a half-wave doublet
or other tuned antenna with transmission line impedances from 52 to 600 ohms. Antenna connections are made to a
three terminal strip at the rear of the receiver marked "A1", "A2", and "G". Mounting holes are also provided, ad-
jacent to the antenna terminals, for installation of an AN type SO-239 connector for coaxial cable installations.
A. SINGLE WIRE ANTENNA
The Simplest antenna and one which will provide
satisfactory results throughout the entire tuning range is
a conventional single-wire antenna. In most localities,
good results can be obtained with just the 15-foot length
of antenna wire suppliedwith the receiver. (See Fig. 2.)
Simply attach one end of this wire to terminal" A1", and
"G", and then run the wire about the room in any con-
venient manner. If the receiver is operated in a steel
constructed building or where receiving conditions are
exceptionally poor, an outside antenna, 50 to 100 feet
long, may be necessary. The outside antenna should be
erected as high as possible and kept free from surround-
ingobjects. In some locations, reception may be improv-
ed by connecting a ground wire (ordinary copper wire)
from terminal" G" to a cold water pipe or outside ground
rod. While the use of an outside ground rod installed in
accordance with Insurance Underwriter's Laboratories
requirements is adequate protection against lightning, we
strongly recommend anadditional connection to the near-
est cold water pine to eliminate any shock hazard.
B. HALF·WAVE DOUBLET ANTENNA
For top performance, especially on the short-
wave and amateur bands, the use of a half-wave doublet
or other type of antennaemployinga 52 to 600-ohm trans-
mission line is recommended. A typical doublet antenna
installation is shown in Fig. 3. The double antenna
should be cut to the proper length for the most used fre-
-3-
9261391-C
Fig. 2. Single Wire Antenna
Fig .. 3. Doublet Antenna Using
Twin-Lead Transmission Line

quency or band of frequencies. The overall length in feet of a doublet antenna is determined by the following formula:
468
Length in feet = Frequency in megacycles
The doublet antenna is directional and should be erected with its entire length facing a desired station for maximum
signal pickup.
The doublet antenna may be fed with either a balanced or unbalanced transmission line. When a balanced line such
as "twin-lead" or a twisted pair is used, the line connects to terminals "AI" and "A2" and the jumper link between
"A2" and "G" is disconnected. (See Fig. 3.) When using an unbalanced line such as coaxial cable, the inner conductor
connects to terminal "AI", the outer metal braid connects to terminal "A2", and the jumper link connects between
terminals "A2" and "G". A ground wire may improve reception when using an unbalanced type line.
By feeding the doublet antenna with a transmission line having an impedance of 300 ohms, a broader frequency
response is obtained than that possible with a 50-75 ohm line.
The doublet antenna provides optimum performance only at the frequency for which it is cut. Therefore, it may
be desirable for reception on frequencies remote from the antenna frequency to utilize the antenna as a single wire
type. This is accomplished by connecting the two transmission line leads together and connecting them to terminal
"AI". The jumper link in this case should be connected between terminals "A2" and "G".
In an installation where the receiver is used in conjunction with a transmitter, it may be advantageous to use the
same antenna for receiving as for transmitting. This is especially true when a directive antenna is used since the
directive effects and power gain of the transmitting antenna are the same for receivin& as for transmitting. Switching
of the antenna from the transmitter to the receiver may be accomplished with a double-pole, double-throw antenna
changeover relay or knife switch connected in the antenna leads.
For further information regarding antennas, refer to the "Radio Amateur's Handbook" or the "A.R.R.L. Antenna
Book", both published by the American Radio Relay League, West Hartford, Conn., U.S.A.
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MOUNTING roR
GO-AXIAL GABLE
CONNECTOR
The receiver is deSigned to operate directly on 105 to 125 volt, 50-60 cycle AC current. Provision has also been
made in the receiver for operation from an external DC power source for portable or emergency service. in areas
where AC power is not available. Connections to the DC source are made through the DC POWER SOCKET at the rear
of the receiver. (See Fig. 4.)
A. AC OPERATION
Insert the power cord into any convenient AC power outlet of the proper rating. If in doubt about your power
source, contact your local power company before plugging in the reCeiver. The wrong power source can cause serious
damage.
IMPORTANT: The receiver will not operate from an AC source unless the JUMPER PLUG is inserted in the DC
POWER SOCKET. (See Fig. 4.)
B. DC OPERATION
The receiver may be operated from an external DC source, such as a vibrator power supply or batteries by
removing the JUMPER PLUG normally located in the DC POWER SOCKET. at the rear of the receiver and replacing it
with a similar octal plug wired as shown in Fig. 5. This plug is available from your Hallicrafters dealer under Part.
No. 35A003. The voltage and current requirements for DC operation are as follows: "B" supply, 280 volts at 105 ma;
"A" supply, 6.3 volts at 4.1 amps.
- 4 -

BA TTERIES
2-5. SPEAKER
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Fig. 5. Wiring Diagram for DC Operation
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A three-terminal strip, marked "G", "3.2" and "500", is provided at the rear of the receiver for connecting the
external speaker that is required with the receiver. (See Fig. 4.) Any permanent magnet speaker with a 3.2-ohm voice
coil can/be used by simply connecting the two leads from the speaker voice coil to the terminals marked "3.2" and
"G". If it is desired to use a speaker with a voice coil impedance other than 3.2 ohms, a matChing transformer should
be emplqyed to insure optimum performance. The transformer should be mounted on or near the speaker, and should
have a 5 watt power rating, a 500-ohm primary impedance, and a secondary impedance to match the impedance of the
speaker voice coil. Connect the primary of the transformer to the terminals marked "500" and "G" and the secondary
to the speaker voice coil terminals.
\The Hallicrafters R-46B and R-47 speakers are both designed for use with your receiver. Either speaker may be
connected to the terminals marked "3. 2" and "G'·.
2-6. HEADPHONES
The headphone jack, marked PHONE, is located on the front panel of the receiver and is wired so that the speaker
is automatically silenced when the headphones are plugged in. The headphone output impedance's not critical, and any
commercial low-impedance headphones ranging from 50 ohms to 5000 ohms will provide satisfactory performance.
TO CATHODE CIRCUITS
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Re cei ve-Standby Cir cuits
- 5 -

2-7. RECORD PLAYER CONNECTIONS
A phono jack is provided at the rear of your receiver for attaching a record player. (See Fig. 4.) Any record
player using a crystal cartridge, or a magnetic cartridge with a suitable pre-amplifier, will provide satisfactory
results. For phono operation, insert the pin-plug from the record player or pre-amplifier into the phono jack and set
the SELECTIVITY control on the front panel at "PHONO". Adjust the VOLUME control for the desired volume level
and set the RESPONSE control'at either "NORMAL" or "TREBLE CUT" for the desired tone. The remaining controls
are inoperative and will have no effect on phono operation.
2-8. RELAY AND TRANSMITTER SWITCHING
One half of the dpst RECEIVE-STANDBY switch on the front panel connects to pins 2 and 5 of the DC POWER
SOCKET
at the rear of the receiver, and is available for transmitter switching. (See Fig. 6.) This half of the switch
is in the open position when the RECEIVE-STANDBY switch is set at "STANDBY" and closed when set at "RECEIVE".
2-9. REMOTE RECEIVE-STANDBY SWITCH
The receiver may be disabled from a remote location by connecting a remote spst switch between pins 1 and 4 of
the JUMPER PLUG located in the DC POWER SOCKET at the rear of the receiver. (See Figs. 4 and 6.). To operate
the receiver with the remote switch, the RECEIVE-STANDBY switch on the front panel must be left at "STANDBY".
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Fig. 7. Operating Controls
SECTION 3.
FUNCTION OF OPERATING CONTROLS
3-1. SENSITIVITY CONTROL
The SENSITIVITY control varies the gain of the RF amplifier, 1650 kc IF amplifier, and 50.5 kc IF amplifier
stages. Maximum sensitivity is ,obtained with the control set at "10"(fully clockwise}. In this pOSition, the tubes being
controlled are operated at maximum gain with minimum cathode bias. As the control is rotated counterclockwise the
bias on the tubes increases with a resultant decrease in gain. '
3-2. BAND SELECTOR CONTROL
The BAND SELECTOR control operates the band switch to place the proper set of coils and sections of the main
and bandspread tuning capacitors into the circuit to cover the desired frequency range. The frequency range covered
by each position of the BAND SELECTOR control is indicated directly on the control.
3-3. ANTENNA CONTROL
The ANTENNA TRIMMER control operates a variable capaCitor connected across the secondary of the antenna coil
of the band in use. This capacitor adjustment compensates for loading effects of various types of antenna installations.
The control is normally adjusted for maximum signal with the MAIN TUNING control adjusted to the high end of the band
in use. With most antenna systems, the ANTENNA TRIMMER control requires no further adjustment until the BAND
SELECTOR control is operated to select another band.
- 6 -

3-4. VOLUME CONTROL
The VOLUME control adjusts the audio level at the speaker terminals and PHONE jack. Clockwise rotation of the
control increases the signal applied to the grid of the audio amplifier tube, thus increasing receiver volume; counter-
clockwise rotation decreases volume.
3-5. AVC SWITCH
The AVC switch, when set at "ON", places the AVC circuit in operation to maintain the output level of the receiver
constant regardless of normal input-signal variations. AVC voltage is applied to the RF amplifier stage and the 1650
kc IF amplifier stage.
3-6. NOISE LIMITER SWITCH
This switch, when set at "ON", places the automatic series noise limiter circuit in operation to reduce pulse type
noise such as ignition noise and electrical interference. The limiter circuit allows the signal to pass through the
receiver unaffected, but makes the receiver inoperative for noise amplitudes greater than those of the signal. It will
work equally well on AM or CW signals and is self-adjusting, i. e., it automatically adjusts itself to the signal level.
The noise limiter circuit" chops" noise peaks received at the detector by means of a biased diode which becomes
non-conducting above a predetermined signal level. When the limiter circuit is in operation, the audio output of the
detector must pass through the limiter diode to the grid of the audio amplifier. The limiter diode normally acts as a
conductor for the audio si-gnal as long as the diode plate is positive with respect to its cathode. When a noise peak is
higher in amplitude than the Signal, it instantaneously swings the cathode positive with respect to the plate, conduction
ceases, and that portion of the signal is automatically cut off from the audio amplifier. The point at which the limiter
diode becomes non-conducting is made sufficiently high so that the diode will not Clip modulation peaks and thus impair
intelligibility, but yet low enough to limit the noise peaks effectively.
3-7. AM/CW-SSB SWITCH
This switch, when set at "CW-SSB", applies plate voltage to the beat frequency oscillator (BFO) to render it opera-
tive for the reception of CW or single-sideband signals. The beat frequency oscillator employs a Hartley oscillator
circuit and is voltage regulated to insure high stable operation. The "AM"position of the AM/CW-SSB switch disables
the BFO for normal reception of standard broadcast and AM phone signals. This switch also changes the AVC time
constant for CW-SSBreception. Inthe CW/SSB pOSition the time constant is made longer, to provide better AVC opera-
tion for SSB.
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3-8. SELECTIVITY CONTROL
The SELE CTIVITY controlis used to vary the selectivity of the receiver to fit receiving conditions. Five degrees of selectivity
are available, ranging from 500 cycles, for CW reception under crowded band conditions, to 5 kilocycles for maximum fidelity for
broadcast reception. The five selectivity positions are shown on the SELECTIVITY control and indicate receiver selectivity at 6 db
down. A
sixth position on the control, marked "PHONO", disables all the receiver circuits except the audio system for phonograph
operation.
The receiver IF selectivity curves are shown in Fig. 8. Note that as the selectivity is varied from a sharp to a broader position,
the i-f passband not only increases but also centers about a higher frequency.
For broadcast reception, the SELECTIVITY control is normally set at "5 KC", the position affording broadest selectivity. Se-
lectivity may be progressively increased by turning the control to the positions marked "3 KC"', "2 KC", "I KC", and "5 KC". For
reception of the crowded amateur and shortwave bands, it is generally advisable to sacrifice fidelity for greater selectivity, since
the added selectivity red.uces both adjacent-channel interference and background noise by attenuating the higher audio frequencies.
Too much selectivity on AM signals, however, will attenuate the high audio frequencies to such an extent that the signal may be-
come unintelligible as a result of excessive side-band cutting. When receiving CW signals, the sharpest selectivity pOSition may
be used without the loss of intelligibility experienced in AM reception.
3-9. "T" NOTCH FILTER
The notch filter circuit provides a means of eliminating or reducing the interfering effect of certain types of heterodynes or CW
signals. To obtain maximum results from this feature of your receiver the use of the two controls associated with the notch filter
circuit are fully explained below.
GENERAL
The manner in which the notch filter will affect the i-f selectivity of the receiver is illustrated on page seven of your instruction
book. As shown in Fig. 9 the filter will suppress an extremely narrow band of frequencies within the i-f band pass range of the re-
cei ver. The effectiveness of this notch is many times greater than the notch of a quartz crystal filter at 400 kc t02 mc. The NOTCH
FREQUENCY control will move the band of suppressed frequencies represented by the notch in the selectivity curve, to any point
within the i-f passband. The NOTCH DEPTH control will vary the depth of the notch in the selectivity curve to control the degree
of rej ection of the interfering signal.
Extensive field testing of this feature has shown that the notch filter is highly effective in suppressing the type of interference
for whi'ch this type of circuit is intended. It must be appreCiated, however, that any selective i-f filter circuit, including the phasing
notch of quartz crystal circuits, affects only a limited range of interfering frequencies. The effectiveness of the notch filter is
therefore somewhat dependent upon the exact nature of the interfering signal. For example: a heterodyne within the i-f range that
is less than 900 cycles in width and has little harmonic content is readily notched out. If the same interfering heterodyne is rich in
harmonics it would only be possible to completely suppress the fundamental frequency and the remaining harmonic content may re-
main almost equally objectionable. It logically follows that if two interfering heterodynes should appear within the i-f pass band that
are separated infrequency by more than 500 to 900 cycles it would be possible to notch out only one of the heterodynes. The inter-
fering Signal may also vary in frequency beyond the range of the notch filter and thus reduce the effectiveness of the circuit. Under
these conditions, increasing selectivity will generally eliminate its heterodyne. If this heterodyne interference varies in frequency
about some mean value it may be necessary to offset the notch depth control to increase the broadness of the notch. It has been
found, however, that the notch filter is sufficiently effective in many instances to make an otherwise useless signal entirely readable.
3-10. USE OF CONTROLS
To activate the Notch Filter circuit advance the NOTCH DEPTH control from the "OFF" position.
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NOTCH FREQUENCY CONTROL - This control tunes the notch in the i-f pass band and may be set anywhere in the range of
from 50 kc to 54 kc. The approximate frequency is calibrated on the knob skirt. While tuning this control for maximum suppression
of the interfering heterodyne with minim~m distortion to the desired signal, try to visualize the notch moving across the selectivity
curve, Fig. 9. It is then readily apparent that improper tuning may notch out the desired signal instead of the heterodyne. It may
be necessary to move the notch across the desired signal in order to reach the heterodyne that you desire to suppress. The im-
portant consideration is to tune the NOTCH FREQUENCY control for maximum heterodyne suppression with minimum distortion to
the desired signal.
NOTCH DEPTH CONTROL - As the position of the NOTCH FREQUENCY control is changed, the depth of the notch will vary.
The NOTCH DEPTH control is provided to retune the notch for maximum depth at any setting of the NOTCH FREQUENCY control
Maximum notching occurs at the "0" setting when the frequency is set to the center of the i-f pass band. The use of the NOTCH
DEPTH control is simply a matter of tuning it for maximum suppression each time the position of the NOTCH FREQUENCY con-
trol is changed.
3-11. PITCH CONTROL
The PITCH CONTROL operates the tuning slug in the BFO coil to vary the frequency of beat frequency oscillator approximately
2 kc each side of its center frequency of 50 kc. The primary function of the PITCH CONTROL is to vary the pitch of the audible beat
note when receiving CW signals. It is also used when receiving Single-sideband signals to vary the frequency of the reinserted
carrier in the receiver.
3-12. RESPONSE CONTROL
The RESPONSE control performs three functions: (1) it turns the receiver on and off, (2) it switches the 2nd conversion oscil-
lator to operate atthe required frequency for reception of CW, AM, and single-sideband signals (1600 kc in the "LOWER SIDEBAND"
position and 1700 kc in the "UPPER SIDEBAND", "TREBLE CUT", and "NORMAL" positions), and (3) it serves as a two-position
tone control for AM reception and phono operation.
In the "POWER OFF" position, the recei ver is inoperative. As the control is turned clockwise to any of the other four positions,
the receiver is turned on.
The "LOWER SIDEBAND" and "UPPER SIDEBAND" positions of the control are us'ed when receiving single-sideband signals or
when it is deSired to receive only one sideband of an AM signal.
The "TREBLE CUT" and "NORMAL" pOSitions are used for phono operation and for normal AM reception where both sidebands
are received. In the "NORMAL" position, the audio response is essentially flat at the low- and mid-frequencies and slightly at-
tenuated at the high frequencies. The response in the "TREBLE CUT" position is essentially the same except that the high fre-
quencies are attenuated considerably more than in the "NORMAL" position.
For CW reception, the setting of the RESPONSE control is immaterial although a slight improvement in signal-to-noise ratio
will be obtained in the "LOWER SIDEBAND" and "UPPER SIDEBAND" positions.
To illustrate how selectable sideband reception is accomplished in the receiver, a numerical example is given. Consider an
incoming signal at 7000 kc, modulated 1 kc. Since modulation of a carrier causes the generation of sideband frequencies numeri-
cally equal to the carrier frequency plus or minus the modulation frequency, the incoming signal consists of the carrier at 7000 kc,
a lower sideband at 6999 kc, and an upper sideband at 7001 kc. (See Fig. lOA.)
The incoming Signal is first heterodyned with the output of the 1st conversion oscillator in the 1st mixer stage. The 1st con-
version oscillator operates at a frequency higher than the incoming signal by an amount equal to the first-intermediate frequency
of 1650 kc. As a result of the frequency conversion process, three new lower frequencies are produced in the output of the 1st
mixer: the carrier at 1650 kc, the lower sideband at 1651 kc, and the upper sideband at 1649 kc. (See Fig. lOB.) These Signals
are amplified by the 1650kc IF amplifier stage and then heterodyned with the output of the 2nd conversion oscillator in the 2nd mixer
stage. The 2nd conversion oscillator is crystal controlled and can be set to operate at either 1600 kc for reception of the lower
Sideband or 1700 kc for the reception of the upper sideband, selection being made by means of the RESPONSE control. When the
RESPONSE control is set at "LOWER SIDEBAND", the 1600 kc signal from the 2nd conversion oscillator is heterodyned with the
incoming signal at the first-intermediate frequency of 1650 kc to produce three new frequencies: the carrier at 50 kc, the lower
sideband at 51 kc, and the upper sideband at 49 kc. By referring to Fig. 10C, it can be seen that the lower sideband falls within the
i-f passband and the upper sideband falls outside of the passband. Thus the lower sideband is accepted and the upper sideband is re-
jected. When the RESPONSE control is set at "UPPER SIDEBAND", the 1700 kc Signal from the 2nd conversion oscillator is heter-
odyned with the incoming signal. In the frequency conversion process, the carrier still remains at 50 kc, but now the upper side-
band appears at 51 kc, and the lower sideband appears at 49 kc. (See Fig. 10D.) Thus, the upper sideband IS accepted and the
lower sideband is rejected.
3-13. CALIB. ON-OFF SWITCH
The CALIB. ON -OFF switch controls the operation of the built-in crystal calibrator. When the switch is set at "ON", the crystal
calibrator is turned on to provide marker signals at every 100 kc on the dial. The crystal calibrator employs a crystal controlled,
pentode oscillator circuit. The output of the crystal calibrator is capacitively coupled to the antenna input circuit. A trimmer ca-
pacitor, adjustable by the CRYSTAL ADJ control on the top of the calibrator unit, permits adjustment of the calibrating crystal to
exactly 100 kc by comparison with the frequencies transmitted by WWV. This capacitor has been set at the factory and should nor-
mally not require periodic readjustment unless extreme calibration accuracy is required. If adjustment is required, proceed as
outlined in Section 4-8.
3-14. RECEIVE-STANDBY SWITCH
The RECEIVE-STANDBY switch, normally set at "RECEIVE", permits disabling of the receiver during transmission periods,
atthe same time maintaining the heater and plate supplies operative for instant use when reception is again resumed. The receiver
is disabled by setting the RECEIVE-STANDBY switch at "STANDBY".
One
section ofthe RECEIVE -STANDBY switch is available for relay or transmitter switching. For connections and details, re-
fer to Section 2-8.
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3-15. TUNING and BANDSPREAD CONTROLS
The TUNING and BANDSPREAD controls are used in conjunction with one another to tune in the desired signal.
Wide tuning is performed with the TUNING control and fine tuning with the BANDSPREAD control.
Main Tuning Dial. The main tuning or left-hand dial is operated by the TUNING control. This dial has four
calibrated scales, one for each of the four frequency bands covered by the receiver. It also contains a hundredths
scale, used with the unit scale on the MAIN TUNING knob, for accurately logging and relocating stations of special
interest. The logging number is the logging number on the dial plus the number on the knob scale. For example;
if the main tuning dial logging scale reads 12, and the MAIN TUNING control knob scale reads 25, the logging
number is 1225. For normal tuning, the main tuning dial is set for the desired station frequency after the BAND-
SPREAD control has been set fully counterclockwise (bandspread tuning capacitor set at minimum capacity) .
IMPORTANT: The readings on the main tuning dial will correspond to the station frequencies only if the
BANDSPREAD control is set fully counterclockwise. If it is set at any other setting, the additional bandspread
capacity added to the main tuning capacity will throw off the main tuning dial· calibration because the receiver
has been calibrated with, the bandspread tuning capaCitor set at minimum capacity.
The dial settings for the 80, 40, 20, 15, and 11-10 meter amateur bands are indicated on the main tuning
dial by white dots. When tuning the amateur bands with the bandspread dial, the main tuning dial must be set
at the dot corresponding to the desired amateur band. The~, meter amateur band is indicated on the dial by
three short double-weight lines.
NOTE
The broadcast band is marked with a "CD" emblem and a dot at .64 and 1.24 megacycles to indicate the
two official civil defense frequencies, In a civil defense emergency, tune to either of these two frequen-
cies for official defense news, instructions, and information.
Bandspread Dial. The bandspread or right-hand dial is operated by the BANDSPREAD control. This dial
contains five scales calibrated for the 80, 40, 20, 15, and 11-10 meter amateur bands. These five scales are
calibrated to read receiver frequency directly when the main tuning dial has been set to the index dot of the
desired amateur band. It also contains a hundredths scale for logging purposes. The logging procedure for the band-
spread dial is the same as for the main tuning dial. For convenience in tuning, the AM phone bands are indicated
on the bandspread dial by double-weight lines.
In addition to its use on the amateur bands, the bandspread dial may also be utilized as a fine tuning adjust-
ment over any portion of the receiver tuning range. Two methods of fine tuning are described below.
a. The first method of fine tuning is used when it is desired to tune in a single signal with precision
accuracy. First the BANDSPREAD control is set a few degrees from its full counterclockwise pOSition, then
the desired signal is located with the TUNING control, and finally the signal is accurately tuned in by "rocking"
the BANDSPREAD control (turning it slightly to the left and right) until the signal is loudest and clearest.
b. The second method of fine tuning is used when it is desired to tune through a range of frequencies, such
as a group of shortwave stations. Set the BANDSPREAD control fully counterclockwise, set the TUNING control
for the high end of the selected range of frequencies, and then tune through the range with the BANDSPREAD
control. Turning the BANDSPREAD control clockwise tunes the receiver progressively lower in frequency.
4-1. AM RECEPTION
SECTION 4·
OPERATION
1. Set the front panel controls to their starting positions as outlined below.
SENSITIVITY .............. , 10 (maximum sensitivity)
SELECTIVITy .............. 5 KC
BAND SELECTOR .......... At the desired band.
RESPONSE ................. POWER OFF
VOLUME .................. ° (minimum volume)
RECEIVE-STANDBy ........ RECEIVE
AVC ON-OFF .............. ON NOTCH
DEPTH ............. OFF
NOISE LIMITER OFF-ON .... OFF
CALIB. ON-OFF ........... OFF
AM/CW-SSB ............... AM
2. Turn the receiver on by rotating the RESPONSE control clockwise and set it at either the "NORMAL" or
"TREBLE CUT" position. The tuning dials will light up indicating the receiver is operative. Rotate the
VOLUME control clockwise for the desired volume level.
3. Set the bandspread tuning gang at minimum capacity by rotating the BANDSPREAD'control fully counterclock-
wise. To utilize the BANDSPREAD control as a fine tuning adjustment for the amateur and shortwave bands,
refer to Section 3-15.
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