Drake R-4A Service manual

TABLE OF CONTENTS

General Specifications

I General Description

II Installation Instructions

Unpacking Location

B. C. Power Requirements D. Antenna Requirements

Speaker Requirements

E. F.

Anti-VOX

G. Muting

III Control Functions

Front

Rear Jacks

Side Controls

IV Operation

Jacks

6 6 6 6 7 7 7

11 12

D. E. F. G. H. I.

V Theory

B. c.Second Converter D. E. Detector Systems F. Audio Output G.AVC System H.

J. K.

Preliminary Control Settings Single Sideband or Double Sideband Suppressed Carrier Reception C. W. Reception

AM Reception

RTTY Reception

Adjusting Dial Calibration

Noise Blanker Operation Operation of Notch Control

Accessory Frequency Coverage

Fixed Frequency Operation

of Operation

R. F. Amplifier First Mixer and Premixer System

50 KC I. F. System

S Meter Noise Blanker Crystal Calibrator Power Supply

13 13 14 14

15 15 16 17 20

21 21 22 22 22 24 24

24 25 25 25

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VI Service Data

A, Removing Top Cover

Removing Bottom Cover

B. C. Tube Replacement D. Troubleshooting

VII Alignment Instructions

50KC Oscillator Alignment

50KC I. F. Alignment

Crystal Filter and Filter Match Transformer

Alignment

5595 KC Oscillator Alignment

Antenna RF, and Injection Circuit Alignment

100 KC Calibrator Alignment

V.F.O. Adjustment

Notch Filter Alignment

Passband

Bias and S-meter adjustment

Tuner Alignment

27 27 27 27

33 33 34

35 35

35 35 36

Fig.# 1 Fig.

# Fig.# Fig.

# Fig.

Fig.

# Fig.

# #

10 11 12 13

Fig. Fig.# Fig., Fig.

CHARTS AND ILLUSTRATIONS

Connecting R-4A to TR-4 Transceiver

Viewing Angle Option

Rear View

Crystal Freg. Chart

Pre selector Chart

Selectivity C urve s

Notch Curves

Block Dia gram

Voltage Chart

Resistance Chart Top View Bottom View Schematic Diagram

8 12 18 19

23 23 26 28

29 30 31

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GENERAL

SPECIFICATIONS

FREQUENCY COVERAGE: and 28.5-29.0 MC with crystals supplied.

3.5-4.0 MC,

7.0-7.5Mc,

14.0-14.5,

Ten accessory crystal sockets

21.0-21.5,

are provided for coverage of any 10 additional 500 KC ranges between 1.5

and 30 M

SELECTIVITY: Drake tunable

C with the exception of 5.0-6.0 MC.

passband

KC at 6 DB down and 2.6 KC at 60 DB down

filter provides:

1.2 KC at 6 DB down and 4.8 KC at 60 DB down

2.4 KC at 6 DB down and 8.2 KC at 60 DB down

4.8 KC at 6 DB down and 20 KC at 60 DB down

Selectivity switching is independent of detector and AVC switching.

I. F . FREQUENCIES:

First I. F.

5645 KC crystal lattice filter; second I.F.

50 KC tunable L/C filter.

STABILITY: Less than 100 cycles after warm up.

Less than 100 cycles for 10%

line voltage change.

SENSITIVITY: Less than

uv for 10 DB signal plus noise to noise on all

amateur bands.

MODES OF OPERATION: SSB, CW, AM, RTTY

DIAL 5 KC

CALIBRATION: Main dial calibrated divisions. Vernier dial calibrated 0

0 to 500

to 25 KCin

and500 to 1000

1 KC

divisions.

CALIBRATION ACCURACY: Better than 1 KC when calibrated at nearest 100 KC point.

AVC: Amplified delayed AVC having slow

sec

.) or fast (. 025 sec.) discharge; less than 100 microsecond charge. AVC can also be switched off. 3 DB change in AF output with 60 DB change in RF input.

AUDIO OUTPUT: 1.4 watts max. and .5 watts at AVC threshold.

AUDIO OUTPUT

IMPEDANCE: 4 ohms and hi impedance for anti-vox.

ANTENNA INPUT: Nominal 52 ohms.

SPURIOUS RESPONSES: Image rejection more than 60 DB. I. F. rejection

more than 60 DB on ham ranges.

Internal spurious responses in ham ranges

less than the equivalent 1 uv signal on the antenna.

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TUBES AND SEMICONDUCTORS:

TUBE

12BZ6

12BA6 6HS6 6HS6

12BE6

12BA6

12BA6 2N3394 2

2N3394

6EH5

12BA6 12AX 7A 2N706 2N3858 2N3394 lN714

0B2 and lN483A

lN3194

lN270

lN483A

lN483A 2 -lN270

lN483A

and

2N3394

FUNCTION

R.F. amp.

100 KC calibrator 1st mixer

Premixer

2nd mixer and xtal oscillator 50 KC I.F.

50 KC I.F. AVC amp./AVC det. Audio amp. Audio output

Noise blanker amp. Noise blanker amp. /shaper VFO VFO buffer Xtal oscillator Voltage regulator Voltage regulator Power supply rectifiers Bias rectifier

AM detector

Noise blanker pulse clippers Noise blanker gate Switching Prod. det.

FRONT PANEL CONTROLS: Main tuning, AF gain, RF gain, SSB/CW-AM

with slow AVC, fast AVC, or AVC off, function switch, band

switch, passband tuning and selectivity, preselector, notch, and head-

phone jack.

REAR AND SIDE JACKS AND CONTROLS: S-meter zero, notch adjust,

antenna jack, speaker jack, mute jack, anti-vox jack,

jack, accessory power socket,crystal lock socket, xtal/VFO switch, ground post ,

POWER CONSUMPTION: 60 watts,

DIMENSIONS:

overall length

and fuse post.

5-l/2”

12-l/4”,

high,

weight 16 lbs.

l0-3/4”

120/240

wide, cabinet depth

VAC,

T4/T4X

50/60

switch,xtal

injection

cycles.

ll-5/8”,

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I GENERAL DESCRIPTION

The DRAKE R-4A is an extremely versatile communication receiver de-

signed to bring you every feature desirable for the ultimate in the

reception of all modes of amateur communications.

It provides a linear permeability-tuned solid state VFO with 1 KC

readability, and premixed injection with crystal controlled high frequency oscillator for stability on all bands.

A 100 KC crystal calibrator is built-in.

An improved

passband

tuner/filter with four selectivity positions, and a built-in notch filter are incorporated to provide the desired selectivity and interference rejection,

and a noise blanker is built-in for elimination

of most noise on CW, SSB and AM.

As supplied, the unit gives complete coverage of 80, 40,

20, and 15

meter bands as well as the 28.5 MC to 29 .O MC portion of 10 meters. Ten accessory crystal sockets are provided for coverage of other 500 KC frequency ranges between 1.5 and 30 MC such as 160 Meters, MARS frequencies,WWV, short wave broadcast, etc. These sockets can be programed to give up to 5 MC of continuous coverage for convenient use

with V. H. F. converters. The R-4A also includes time proven DRAKE AVC with

fast-attack/slowrelease for SSB or AM and fast-attach fast-release for CW. If desired, the AVC can be completely disabled for CW reception.

Complete AVC action and accurate S-meter indication can be obtained, on all modes.

A crystal-lattice filter following the first mixer provides

excellent overload characteristics by providing selectivity before gain

producing stages.

When used with our T-4 Reciter, transceive operation may be obtained,

and when used with the T-4X transmitter, either transceive or independent receive and transmit functions are possible.

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II INSTALLATION INSTRUCTIONS

UNPACKING

Carefully remove your R-4A from the packing carton and examine it closely for signs of shipping damage. Should any be apparent, notify the delivering carrier immediately, stating the full extent of the damage.

Fill out and mail the enclosed warranty registration card so that your

warranty will be effective.

Save the packing material.

You may need it later for reshipment or storage.

Inspect the packing material closely before putting it away to be sure that you have not overlooked any accessory hardware.

LOCATION

In general the location of the R-4A is not critical. However, care should be taken to insure that space is allowed around the unit for adequate air circulation. Extremely hot locations, units,should be avoided.

papers,

or pieces of equipment,as overheating may result.

Do not cover the top of the R-4A with books,

such as near radiators or heating

POWER REQUIREMENTS

The R-4A is supplied with a dual-primary power transformer and can be operated from 120 or 240 volt

50/60

it is wired for 120 volt operation.

cycle AC. As supplied from the factory,

If 240 volt operation is desired, it will be necessary to remove the black/yellow and black/green power transformer primary wires from the terminals to which they are now connected and connect them together at the unused terminal on the same terminal strip.

75 amp fuse supplied with the

It will also be necessary to replace the

unit with a

amp Slo-Blo fuse for adequate protection at the increased

voltage (see schematic diagram).

ANTENNA REQUIREMENTS

The R-4A is designed to give best results when used with an antenna resonant

on the operating frequency and having an impedance from 50 to 75 ohms. This requirement is most easily met using a center-fed dipole antenna cut to the desired frequency and fed with

RG58A/U

cable. However, there are

many other antennas which will fulfill this requirement. For a more detailed

de scription on antennas ,

we suggest you refer to the ARRL Antenna Book or

The Radio Amateur’s Handbook.

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Antenna connection to the R-4A is provided at the jack on the rear of the

chassis marked ANT.

It is recommended that when the R-4A is used with a transmitter, the transmitting antenna be used; change-over being accomplished by an antenna

relay.

This function is provided

internally in our model T-4 and T-4X

Transmitters.

SPEAKER REQUIREMENTS

A good quality 4 ohm speaker should be connected to the jack on the rear of the chassis marked SPKR.

If one lead of the speaker is grounded to its

cabinet, its connection should be to the chassis of the R-4A.

Our accessory speaker model MS-4 provides the correct match, correct tonality for good communications audio, correct connector, and is patible in appearance with the R-4A.

It will also house our model AC-4

com-

power supply which is needed in conjunction with our model T-4 and T-4X Transmitters.

ANTI -VOX

A high impedance output is provided at the ANTI-VOX jack on the rear of

the R-4A chassis for use with our T-4 and T-4X transmitters and other transmitters having voice control capabilities. The impedance at this terminal is approximately 5000 ohms.

If the transmitting equipment requires a lower impedance it may be necessary to attach a matching transformer between the ANTI-VOX terminal on the R-4A and the ANTIVOX input terminal of the transmitter,

or to use the speaker output.

MUTING

The Mute jack on the rear of the R-4A is connected so that when the

function switch is in EXT-MUTE position the receiver will operate only

when the inner-conductor of this jack is shorted to ground, and the

R-4A

will mute when the inner-conductor is open with respect to ground.

The inner-conductor should, therefore, be connected to a relay contact in the transmitter or antenna relay which is normally open when transmitting

and grounded when receiving.

It is recommended that a shielded wire be used between the mute terminal and the relay such as is provided with our model T-4 and T-4X Transmitters.

If external muting is not desired, the STBY and ON positions of the function

switch can be used. Jack to obtain N. B. and CAL functions.

It is necessary to insert a shorted plug in the Mute

Such a plug is installed in each

R-4A when shipped.

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TR-4

y---

This switch must be

in the TCVR position

for transceiving and in the position for separate

receiver use.

lower

Cable

~___.____

Speaker Cable

_~---

Mute Line

RCVR

---I

~__-

AC-4/MS-4

or RV-4

R-4A

FIG.

USING

____--_-_____.p

THE R-4A WITH THE TR-4 TRANSCEIVER

Receiver Antenna Cable

VIEWING

ANGLE OPTIONS

REAR

FE ET REMOVED

OPTION

# 2

~__

___

FIGURE 2

-8-

INVERTED FRONT FEET

FEET REMOVED FROM REAR OF

STUD* 10x24 x SUPPLIED WITH UNIT

5/8

BASE

LONG

A. FRONT

III CONTROL FUNCTIONS

MAIN TUNING - The MAIN

TUNING

knob of the R-4A determines the

frequency on which you are receiving. The vernier skirt around this knob is calibrated in KC’s from 0 to 25. The main dial is calibrated in five KC divisions and has two scale

Use the 0 to

.500

S .

for bands 7.000-7.500, 14.000-14.500, 21.000-21.500, etc.; use

.500

the

to 1.000 scale for bands 1.500-2.000,

3.500-4.000,

29.000, etc. The small red knob just to the right of the dial scale is for adjusting the position of the indicator line for calibrating the main dial. The knob skirt is also adjustable by pushing it in slightly and rotating it in the desired direction while holding the main tuning knob stationary.

BAND

The BAND control is a six position switch used to select the amateur band desired or to switch the RF circuits to the correct tuning range when tuning accessory frequency ranges.

The frequency range

which may be tuned for each setting of the band switch control is

given on the chart on page 16.

XTAL

The XTAL switch is an eleven position switch used to determine which crystal socket will be inserted in the circuit. When it is in the normal position,

crystal selection is accomplished by means of the band switch (with the exception of the 1.5 setting). When this switch is set on any of the other positions 1 through 10, the crystal inserted in the corresponding crystal socket will be inserted in the circuit for accessory band operation.

The BAND switch must then be set in ac-

cordance with the information given on the crystal frequency chart

for reception of the frequency desired.

scale

28.500-

PRESELECTOR

The PRESELECTOR control permeability-tunes the antenna,

RF, and premixer coupling coils to the desired frequency. The logging

scale on this control is calibrated from 0 to 10 with markings showing

the correct settings for the 160 through 10 meter amateur bands.

FUNCTION

The FUNCTION switch is a six position switch used to

select the method of operating the R-4A.

When in the OFF position the power transformer primary is opened,

thus turning the unit off.

When in the STBY position, the power

is connected, thus allowing the filament and B+ to operate but the receiver is muted regardless of external connection. When in the ON position, connection.

the receiver is unmuted regardless of external muting

When in the EXT-MUTE POSITION, the receiver is

muted or unmuted depending upon whether or not the mute connection

on the rear of the chassis is grounded,

-9-

thus permitting external control

the transmitter.

is energized,

and when in the CAL position, the noise blanker is

When in the N. B. position the noise blanker

switched off and the calibrator is switched on. In these last two positions the muting function is the same as if the switch were in the EXT-MUTE position,

so if external muting is not used, a shorted

plug must be inserted in the Mute jack to obtain these functions.

SSB/CW-AM- This switch determines the detector which is used and the AVC mode.

When in the AM position,

a diode detector is incorporated, the BFO is switched off, and the AVC with a slow time constant is used. a product detector with the BFO. delay time is about imately

The other three positions under the heading SSB/CW employ

In the SLOW AVC position the AVC

.025

seconds.

5 seconds.

In the AVC OFF position no AVC is generated.

In the FAST AVC position it is approx-

The SLOW AVC position should normally be used with single sideband and CW and the fast position should normally be used for break-in CW and RTTY. The AVC OFF position should be used only on CW

under difficult conditions in conjunction with the RF gain control.

AF GAIN

The A. F. GAIN knob controls the audio output level of

the receiver.

RF GAIN

The R.F. GAIN knob varies the bias applied to the AVC

controlled tubes thus controlling the R. F. gain of the unit.

NOTCH the receiver’s

carriers .

side the receiver’ s pa ssband.

direction from the center as

The NOTCH control tunes a highly selective notch across

passband

for the purpose of eliminating interfering

When turned to the OFF position, the Notch is moved out-

Rotation of this control is in the same

PASSBAND

control; i. e. If

PASSBAND

set to the left side (lower sideband) then heterodynes will be removed

with NOTCH set left of center.

PASSBAND- The

band selector lever and the

PASSBAND

control is composed of two parts; the

passband

tuning knob. The selector lever

is calibrated in numbers representing the band widths in KC’s at 6 DB

down(.4,

The length and position of the lines which make up the

1.2, 2.4,

and 4.8KC).

passband calibration indicate the relative band widths and their positions with respect to each other.

The pointer on the

Passband

tuning knob repre-

sents the relative position of the fixed 50 KC BFO with respect to the movable passbands. rect settings of the

The dots at the ends of the lines indicate the cor-

PASSBAND

tuning knob for single sideband reception.

All of the left hand dots are for lower sideband and all of the right hand

dots are for upper sideband.

pass-

tuning

-lO-

11.

For CW reception on the .4 position the signal is tuned for most pleasing note with the frequency knob and is then peaked with the PASSBAND

changing the at maximum signal strength will be correct.

PHONE JACK private listening when desired.

speaker output when headphones are plugged in. While the headphone impedance is not critical (adequate output is available for most commercially available phones) more output is obtained on lower impedance phones . Trimm type 56

tuning knob. You can then tune other stations without

PASSBAND

A PHONE JACK is provided on the front of the R-4A for

We recommend a good set of 600 ohm phones, such as the

06.

tuning knob setting. The audio frequency

The jack automatically mutes the

12.

B. REAR CONTROLS

S-METER

ceived signal.

S-9. Each S-unit equals about 5 DB and S-9 is about 30 microvolts

at the ANT terminal.

INJ. JACK

system of the R-4A to the T4 or T4X transmitters so that

operation with these units can be obtained.

SPEAKER JACK

2. connection of a 4 ohm speaker such as our MS-4.

MUTE JACK

3. receiver. EXT-MUTE, N. B., this jack is open from ground. returns the receiver to the receive condition.

ANTI-VOX JACK

JACK for use in energizing the ANTI-VOX circuit of a transmitter used with the unit such as our T-4 and T-4X.

The S-METER indicates relative signal strength of the re-

The receiver is muted when the FUNCTION switch is in the

It is calibrated in S-units from S-l to S-9 and DB over

JACKS

The INJ. jack provides a means of coupling the

The SPEAKER JACK on the rear of the chassis is for the

The MUTE JACK is for externally muting and unmuting the

and CAL positions and when the center conductor of

Shorting the center conductor to ground

High impedance audio is brought out the ANTI-VOX

premixer

transceive

ANTENNA JACK

the R-4A to an antenna. mately 52 ohms and can be used with antennas having impedances between 50 and 75 ohms.

POWER SOCKET

for operating external accessories.

5AB2

connector.

@ 30 ma.

The ANTENNA JACK provides a means for connecting

The input impedance at this point is approxi-

A POWER SOCKET is provided on the rear of the R-4A

This plug mates with a Cinch Type

Maximum load is 6.3 VAC @

-11-

.75

amp and

+150

VDC

+ 27 hidden pages

Drake R-4A Service manual

Specifications and Main Features

Frequently Asked Questions

User Manual