Drake SW-4A Instruction Manual

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TABLE OF CONTENTS


SECTION			PAG E
I	SPECIFICATIONS		l - 3
II	INSTALLATION	4		- 8
III	OPERATION	9		- 16
IV	SERVICING	17		- 20

ILLUSTRATIONS AND TABLES					PAGE
Figure	1	Rear View			6
Figure	2	Viewing Angle		Options	8
Figure	3	Front	View		11
Figure	4	Block	Diagram		22
Figure	5	Bottom View			23
Figure	6	Top View			24
Figure	7	Schematic Diagram			25
T a b l e	I	Tube	Voltages		21
T a b l e	I I	Resistance to		Ground	21

Section I

Specifications

1.1TUNING RANGES

Band	Frequencies	Tuned	(Megahertz)
.2	.150	to	.500
.5	.450	to	1.050
1.0	.950	to	1.550
6.0	5.950	to	6.550
7.0	6.950	to	7.550
9.5	9.450	to	10.050
11.5	11.450	to	12.050
15.0	14.950	to	15.450
17.5	17.450	to	18.050
21.5	21.450	to	22.050
25.5	25.450	to	26.050

l.2 SENSITIVITY

The SW-4A has a signal-to-noise ratio of 10 decibels with an input signal of 1 microvolt (3 microvolt on .2 band) when the input signal is modulated 30% with 400 Hertz. Simply stated, this means that you get 10 times as much signal output

as noise output from your receiver when you have a signal as small as 1 millionth of a volt on your antenna.

1.3SELECTIVITY

The SW-4A has a bandwidth of 5 kilohertz at 6 dB down and 16 kilohertz at 60 dB down. This selectivity gives adequate bandwidth for optimum reception without allowing significant interference from stations operating near the frequency to which you are tuned.

1.4ANTENNA

The nominal input impedance of the antenna circuit is 52 ohms. This provides excellent reception characteristics with most commer/cial 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 particular band.

1.6OUTPUT

Output impedances of 4 and 8 ohms are provided, The SW-4A has a maximum audio output (volume) of 3 watts, At a 2 watt level, the harmonic distortion is 5%.

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 voltage, either above or below the nominal value , will cause a frequency shift of not more than 100 Hertz.

1.8INTERMEDIATE FREQUENCIES

The first conversion is made at a frequency of 5,645 megahertz, the second at .455 megahertz. A crystal lattice filter is used in the first conversion.

1.9AUTOMATIC GAIN CONTROL

An amplified-delayed automatic gain control circuit is used in the S W - 4 A 90 dB change in R,F, input causes a 3 dB change in audio output, In other words, the volume from the SW-4A does not change much from very weak signals to very strong signals.

1.10POWER

The power consumption of the SW-4A is 30 watts.

1.ll DIMENSIONS

The SW-4A is 5-l/2 inches high, 10-3/4 inches wide, and 12-l/4 inches deep, It weighs 16 pounds.

1.12TUBES AND SEMICONDUCTORS

The SW-4A uses 6 tubes, 7 transistors, and 8 semiconductor diodes, These are listed on the next page.

Section I

Specifications

1.12TUBES AND SEMICONDUCTORS (cont’d.)

Identification

vl v2 v3 v4

Q5, Q6

D5, D6, D7, D 8

Type	Function
12BZ6	Radio frequency amplifier
6HS6	First mixer
12BE6	Second mixer
12BA6	First intermediate frequency
	amplifier
12BA6	Second intermediate frequency
	a mplif ier
6HS6	Premixer
2N3394	Crystal oscillator
2N3858	Buffer for variable frequency
	oscillator
2N706	Variable frequency oscillator
2N3858	Automatic gain control amplifier
2N3394	Audio frequency amplifiers
RCA 40310	Audio output
lN483	Automatic volume control
	clamp
lN714	Volta ge regulator
lN270	Detector
lN3194	Bias rectifier
lN3194	Power supply rectifiers

Section II

Installation

2.1UNPACKING

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 extremely 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 installed long wire antenna, 50 to 75 feet in length,
and located as high in		___
	the air as possible, will give good reception with the
SW-4A. Commercially	available	antennas,	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 lead. The		antenna lead		a
				is connected to

screw terminal (marked ANT) on the rear of the receiver. For .15 - 1.5 mega-

hertz use the accessory DRAKE AL-4 Shielded Directional Loop Antenna if
directional reception is desired.
2.4	SPEAKER

The SW-4A requires an external speaker, which may have an impedance of

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 . The headphone connection is made through the socket marked PHONES at the bottom center of the front panel of the receiver, A standard l/4 inch phono plug will mate with this socket. Connecting the headphones to the receiver will shut off the speaker output.

2.6 POWER

Your SW-4A was shipped from the factory ready for operation from a 120 volt 50 to 60 Hertz (cycles per second) power line. A 3/4 ampere slo-blow fuse (Buss type MDL 3/4) is installed in the fuseholder at the rear of the chassis. If your receiver is to be operated on 120 volts , no changes need be made.

If your line voltage is 240 volts , your receiver is easily adapted to operation at that voltage. Make sure the power cord is not connected. Turn the receiver 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 "120 volts", use a 3/4 amp. fuse. Remove the two (2) screws holding the copper plate to

the chassis, remove the plate, and push the sliding handle of the switch down as far as it will go. Turn the copper plate so the side marked ” 240 volts use " 3/8 amp. fuse” is toward you, and place the plate in position around the switch 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 rear of the chassis) and remove the 3/4 ampere fuse, Obtain and install 3/8 ampere slo-blow fuse (Buss type MDL 3/8) in the fuseholder and tighten the fuseholder cap, Your receiver is now ready for operation on 240 volts.

2.7 GROUNDING

The receiver should be connected to a ground that is as near as possible to earth potential. A cold water pipe will usually make a satisfactory ground

connection,	Either of the screw terminals marked GND may be used for this
connection,	Use a commercial ground clamp for fastening the ground wire

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 REAR V I E W S W - 4 A

the bottom cover of your SW-4A. To do this, first obtain a piece of soft ma-

terial, 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 viewing angle shown in Option #l, 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

2.9ACCESSORIES

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. The body piece has a length of coaxial wire attached at the handle-plug and attached to the wire are 4 eyelets. To assemble the AL-4, first insert the 4 struts into the 4 holes in the aluminum disc part of the body piece. Either end may be inserted. It will probably be easiest to do this with the antenna lying horizontally on a table . Next insert 3 of the eyelets into the ends of 3 of the struts . The 4th eyelet is then inserted into the 4th strut by bending this strut up out of the plane of the other struts; 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 “nulled” out. When there is no interferring station, rotate the loop for maximum strength of the desired signal.

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