Drake SW-4A Instruction Manual
TABLE OF CONTENTS
SECTION
I
II
III
IV
SPECIFICATIONS
INSTALLATION
OPERATION
SERVICING
ILLUSTRATIONS AND TABLES
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Rear View
Viewing Angle Options 8
Front View 11
Block Diagram
Bottom View
Top View
Schematic Diagram
PAG E
l - 3
4
-
9
-
17
-
PAGE
6
22
23
24
25
8
16
20
Table I
Table II
Tube Voltages
Resistance to Ground
21
21
Section I
Specifications
1.1
l.2
TUNING RANGES
Band
.2
.5
1.0
6.0
7.0
9.5
11.5
15.0
17.5
21.5
25.5
SENSITIVITY
Frequencies Tuned (Megahertz)
.150
.450
.950
5.950
6.950
9.450
11.450
14.950
17.450
21.450
25.450
to
to
to
to
to
to
to
to
to
to
to
.500
1.050
1.550
6.550
7.550
10.050
12.050
15.450
18.050
22.050
26.050
The SW-4A has a signal-to-noise ratio of 10 decibels with an input signal of 1
.2 band) when the input signal is modulated 30% with 400
microvolt (3 microvolt
Hertz.
Simply stated, this means that you get 10 times as much signal output
on
as noise output from your receiver when you have a signal as small as 1 millionth of a volt on your antenna.
1.3
SELECTIVITY
The SW-4A has a bandwidth of 5 kilohertz at 6 dB down and 16 kilohertz at 60
down.
This selectivity gives adequate bandwidth for optimum reception without
allowing significant interference from stations operating near the frequency to
which you are tuned.
1.4
ANTENNA
The nominal input impedance of the antenna circuit is 52 ohms. This provides
excellent reception characteristics with
most commercial short-wave antennas,
/
while also giving good performance with properly installed long-wire antennas.
1.5
DIAL CALIBRATION
The tuning dial of the SW-4A is accurate to +- 3 KHz after calibration on a par-
ticular band.
1.6
Output impedances of 4 and 8 ohms are provided, The
audio output (volume) of 3 watts,
OUTPUT
SW-4A
has a maximum
At a 2 watt level, the harmonic distortion is
5%.
dB
Section I
Specifications
1.7
STABILITY
After a five minute warm-up, the SW-4A will not drift more than 100 Hertz
above or below the frequency to which it is tuned, A 10% change in line
age,
either above or below the nominal value , will cause a frequency shift
volt-
of not more than 100 Hertz.
1.8
INTERMEDIATE FREQUENCIES
The first conversion is made at a frequency of 5,645 megahertz, the second
at .455 megahertz
1.9
AUTOMATIC GAIN CONTROL
An amplified-delayed automatic gain control circuit is used in the
dB
90
change in
. A crystal lattice filter is used in the first conversion.
SW-4
R,F,
input causes a 3 dB change in audio output, In other
A
words, the volume from the SW-4A does not change much from very weak sig-
nals to very strong signals.
1.10
The power consumption of the SW-4A is
POWER
30
watts.
1.ll
The SW-4A is
DIMENSIONS
5-l/2
inches high, 10-3/4 inches wide, and 12-l/4 inches deep,
It weighs 16 pounds.
1.12
TUBES AND SEMICONDUCTORS
The SW-4A uses 6 tubes, 7 transistors, and 8 semiconductor diodes, These
are listed on the next page.
Section I
Specifications
1.12
TUBES AND SEMICONDUCTORS
Identification
vl
v2
v3
v4
v5
v6
Ql
Q2
Q3
Q4
Q5,
Q7
Dl
D2
D3
D4
D5, D6, D7, D8
Q6
Type
12BZ6
6HS6
12BE6
12BA6
12BA6
6HS6
2N3394
2N3858
2N706
2N3858
2N3394
RCA
40310
lN483
lN714
lN270
lN3194
lN3194
(cont’d.)
Function
Radio frequency amplifier
First mixer
Second mixer
First intermediate frequency
amplifier
Second intermediate frequency
a mplif ier
Premixer
Crystal oscillator
Buffer for variable frequency
oscillator
Variable frequency oscillator
Automatic gain control amplifier
Audio frequency amplifiers
Audio output
Automatic volume control
clamp
Volta ge regulator
Detector
Bias rectifier
Power supply rectifiers
Section II
Installation
2.1
UNPACKING
Carefully remove the receiver from the shipping carton, and examine it for
evidence of damage
.
If any damage is discovered, immediately notify the
transportation company that delivered the receiver, Be sure to keep the shipping carton and packing material, as the transportation company will want to
examine them if there is a damage claim.
Keeping the carton and packing
material is recommended even when no shipping damage occurs, as having
the original carton available makes shipment of the receiver much easier
should it ever be necessary to return it to the factory for service.
On the front of this manual you will find a brown envelope, which contains a
warranty card and some hardware. Fill our the warranty registration card and
mail it, Lay the hardware aside temporarily. Turn your SW-4A so the rear of
the cabinet is facing you, and check that all tubes and crystals are firmly in
their sockets.
2.2
LOCATION
The SW-4A will work well in almost any location. Avoid placing it in an ex-
,
tremely hot area (such as over a radiator)
and do not restrict air circulation
around the receiver.It is best to leave an inch or more clearance on each
side of the receiver.
2.3
ANTENNAS
Your SW-4A is an excellent receiver, and should be used with an adequate an-
.
tenna system
A carefully
and located as high in the air as possible,
SW-4A. Commercially available antennas,
installed long wire
___
will give good reception with the
antenna, 50 to 75 feet in length,
such as the Mosely SWL-7, will
give even better results. In any case,a standard radio lightning arrester
should be installed in
the antenna
screw terminal (marked ANT) on the rear of the receiver.
hertz
use the accessory DRAKE AL-4 Shielded Directional Loop Antenna if
lead.
The
antenna lead is connected to a
For .15
- 1.5
mega-
directional reception is desired.
SW-4A
SPEAKER
requires an external speaker, which may have an impedance of
2 . 4
The
4 or 8 ohms.The Drake MS-4 Speaker, housed in a cabinet that matches the
SW-4A, provides excellent audio reproduction and comes equipped with a cable
terminated in a phono plug matching the 4 ohm output socket of the receiver,
Screw terminals
, marked 8 ohms and GND are provided on the rear of the SW-4A
for connection of speaker leads if an 8 ohm speaker is used. (See Figure 1).
4.
Section II
Installation
2.5
HEADPHONES
Headphones having an impedance of 500 to 1000 ohms may be used with the
SW-4A. Best results will be obtained with a set of good quality 600 ohm headphones
at the bottom center of the front panel of the receiver, A standard
phono plug will mate with this socket.
The headphone connection is made through the socket marked PHONES
.
l/4
inch
Connecting the headphones to the
receiver will shut off the speaker output.
SW-4A
POWER
was shipped from the factory ready for operation from a 120 volt
3/4
ampere slo-blow fuse
3/4)
is installed in the fuseholder at the rear of the chassis.
,
no changes need be made.
,
your receiver is easily adapted to operation
2.6
Your
50 to 60 Hertz (cycles per second) power line. A
(Buss type MDL
If your receiver is to be operated on 120 volts
If your line voltage is 240 volts
at that voltage. Make sure the power cord is not connected. Turn the receiv-
er so the rear of it is facing you.
At the left side of the receiver, (see Figure
1) near the place where the power cord passes through the chassis, is a switch.
A copper plate surrounds the switch handle, and the plate is marked
3/4
use a
chassis,
the
amp. fuse.
remove the plate, and push the sliding handle of the switch down
as far as it will go.
3/8
amp. fuse” is toward you, and place the plate in position around the switch
Remove the two (2) screws holding the copper plate to
Turn the copper plate so the side marked
"120 volts",
”
240 volts use
"
handle.Install the two (2) screws to hold the copper plate in place, Remove
the knurled cap from the fuse holder (next to the power transformer on the top
3/4
rear of the chassis) and remove the
ampere slo-blow fuse (Buss type MDL
fuseholder cap,
Your receiver is now ready for operation on 240 volts.
ampere fuse, Obtain and install
3/8)
in the fuseholder and tighten the
3/8
2.7
The receiver should be connected to a ground that is as near as possible to
earth potential.
connection,
connection,
GROUNDING
A cold water pipe will usually
Either of the screw terminals
Use a commercial ground clamp for fastening the ground wire
make
a satisfactory ground
marked GND may be used for this
to the water pipe, and make sure the clamp makes solid physical contact with
the pipe.
2.8
VIEWING ANGLE OPTIONS
As supplied, your SW-4A sits with its base parallel to the mounting surface
as its front panel vertical to the mounting surface . Using the hardware that
was packed with your warranty registration card, it is possible to change the
viewing angle.
The top illustration in Figure 2 shows the SW-4A as supplied,
To change to the other mounting shown in Figure 2, it is necessary to remove
5.
,
Section II
Installation
FIG. 1
the bottom cover of your SW-4A.
REAR
VIEW SW-4A
To do this, first obtain a piece of soft material, such as a rubber mat or a blanket, and place it on the work surface.
Turn the SW-4A upside down, and set it on its top cover, on the mat. You
will note two rows of three screws each on each side of your receiver.
To re-
move the bottom cover, remove the rows of three screws that are nearest the
bottom cover, and lift the cover from the receiver.
Next, remove the screws holding the rear mounting feet to the receiver, Near
the holes from which you removed the screws are two other holes,, Take the
small hemispherical rubber feet that were supplied, and snap the cylindrical
portion of these into the holes next to the screw holes,, If you want the view-
#l,
ing angle shown in Option
all that remains to be done is to put the bottom
cover back onto your receiver.
For mounting as shown in Option
#2,
remove the front mounting feet, invert
them, and remount them on the original mounting screws. Then take the two
threaded studs supplied (these look like bolts without heads) and thread them
into the bottom of the inverted mounting feet.
Now screw the mounting feet
that were removed from the rear of the receiver onto the protruding studs, (See
detail drawing at bottom of Figure 2).
Section II
Installation
2.9
ACCESSORIES
In addition to the MS-4 matching speaker, a special loop antenna, Model AL-4
is available.
ASSEMBLY AND USE OF THE ACCESSORY AL-4 LOOP ANTENNA
Assembly
Your AL-4 Loop Antenna is shipped in five separate pieces; 4 struts and 1 body
piece.
and attached to the wire are 4 eyelets.
4 struts into the 4 holes in the aluminum disc part of the body piece.
The body piece has a length of coaxial wire attached at the handle-plug
To assemble the AL-4, first insert the
Either end
may be inserted. It will probably be easiest to do this with the antenna lying
.
horizontally on a table
struts .
The 4th eyelet is then inserted into the 4th strut by bending this strut
up out of the plane of the other struts;
Next insert 3 of the eyelets into the ends of 3 of the
be careful not to bend excessively so
that it will take a permanent set.When the struts and eyelets are in place,
the struts should form shallow “S’s”. This completes the assembly of the AL-4
Loop Antenna.
Use
The AL-4 Loop Antenna handle should be inserted into the hole on the top of
the SW-4A Shortwave Listening Receiver cabinet, and the plug inserted in the
jack on top of the chassis. The AL-4 is intended for use primarily on the 3
lowest bands. For directional effect, disconnect any antenna connected to the
antenna terminal at the rear of the chassis. The antenna is directional in that
it has a very sharp null in two directions. When using the AL-4 (or any other
antenna) quite often there will be interferring stations operating on the same
frequency. To best receive the desired signal, in the presence of an interferring
station, the AL-4 should be rotated until the interferring station is
When there is no interferring station,
rotate the loop for maximum strength of
“nulled”
out.
the desired signal.
7.
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