Realistic Marine Radio Dx 75 Users Manual

DX-75 to the manual f1e76a2d-df05-415e-8a3d-666268f5c8e7

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LtstlcCOMMUN
ICATION REC
EIVER
OPERATING
AND
SERVICE
INSTRUCTIONS

M(IDELDX.I5
RADIO SHACK CORPORATION
D IV IS IONOF TANDYCOR,PORATION

#

INTRODUCTION

Listed

of the many types of broadcasts

below are sone

[hat can be heard on the short wave bands:

The Realistic DX -75 Communications Receiver is desig'ned
to I

Amateur

Radio (Ham)

Mobile Radio - Telepirone

rvideboth the usual "long wave" standard broadcast

recei)tion and'short wave' international broadcastrecep-

Military

tion. Therefore, it allows the listener to span the oceans

Citizens Band (CB)

ald travel around the world by means of radio waves.

lnt. Short Wave (Voice of America, etc. )

of radio waves.

Standard Time Sigrnls (WWV)

GENERAL

Short wave radr,r signals arcused forlong distance transnission becausc of the way they are reflectcd back to
earth by the ionosplx'rc. Radiation frorn space (primarily

Thc Realistic DX-75 is a four band AM receiver which

Ironr thc sut)causes ioniz:ltioll olthe loycrs oI gascs higlt

covcrs the standarcl broadcast frequencies in one band:

above thc carth.

Shott wrr,rt r-acliosignals rvill not pcne-

550 to

1600 KC;

and the short

wave frequencies in

trate t.hcsetonizedgascs; rnst.ead,they bounce back to

t l r r e eb a n d s : 1 . 6 t o 4 . 4 M C ; 4 . 5 t o f l M C ; l l t o 3 0 M C .

earth much like a stone skips across the surface of quiet

Utilizing four tubes (one multipurpose tube affords five

watcr. Variations in thc reflccting charactcristics of tlre

tube perf o rmance ) plus rec tif ie r, the superhetrodyne c i r -

ionospheredue to sun spots, scasons, time of day, etc.,

cuit is designed to operate from a 105 to l25volt, 60 cycle

producc periods when the skipping of short wave signals

power source.

is espccially effective. Sincc nrany of these periods oc-

ard of a hot chassis.

cur h regular cycles the listener may develop a sched-

model cabinet, the receiver features an eight inch "slide

A power transformer eliminates the haz Housed in a vinyl clad steel taple

ule of the best times to listen for sisnals from distant

rule" type dial with continuous tuning of all four bands,

Darts of the world.

plus bandspread for precise location of signals on tie
busy short wave bands.

SPECIF'ICATIONS

OPERATION

Ditncnsions

6 - 5 / 1 6x 1 4 - I / 4 x L t ) - 1 7 / 3 2

VOLUME

Wcight (net)

15 pounds

knob turns on powcl and increascs volume.

Frequency

5 5 0 t o 1 6 0 0K C - 1 . 6 t o 3 0 M C

Rangc

S e n si t i v i t y

Ciockwise

rotation

of t]le Volurne

control

3.5prvat 20 MC (6 db signal-to-

BAND SE,LECTOR

noisc ratio with 30/s mocl. )

switches antenna and local oscillator circuits for the var-

6 d b d o r v n ,1 4 . 5 K C ;

ious tuning bands. Index numbers are located near the

60 db dorvn, I 25 KC

knob and at each end of the diai.

Selectivity

Rotation of the Band Selector knob

Audio Orltput

I .5 warrs

Input Voltage

1 0 5t o 1 2 5v o l t s , 6 0 c p s

TUNING

Power Consumption

35 watts

tuning indicator (red) to move across the dial .

INSTALLATION

Rotation of the Tuning knob causes the main

Rotation of the Bandspread loob affects

BANDSPREAD

a fine tuning adjustmcnt of the reception frequency. NorChoice of a location for
several

tlrc rece iver may bc subject to

mally the indicator should be adjusted to the SET position.

Tlrese include the arrangement

After the approximate frequency has been tuned by use of

considerations.

oI lurnitur-c
listencr,

in thc roon,

thc comfort

ancl convicncc

and acccss to a good electrical

outside antenna.

MarT hours of listening

available from a short wave ll:cciver
ed that the

selection

be carefully

made,

the rnain tuning lcrob, tl-rcbandspread adjustrnent gradually

ground and an

reduces the frequency for pinpoint selection of signals,

enjoyrnent arc

soitis

of a location

of tl'rc

for

recommendthe

BFO

Beat !-requency Oscillator and increases the % of modu-

be

DX-75

Clockwise rotation of the BFO control turns on a

lation of the IF signalby tlris oscillator. A CW signal, as
usecl fol single side band or code telegraphy purposes,

The antenna for
however,

standard

broadcast

an outside antenna is required

ception on the short

wave bands.

As a general

as possible (up to I00 ft.) for best reception

buildings,

range of this control may also improve reception of weak

rule an

and as long

ANL ON

power

etc. , and should be attached to

its supports by glass orceranric

insulators.

ln rfie up position this slide switch activares

the Automatjc Noise Limiter

No. 12 to

circuits designed to mini-

mize background noise, static, etc.

Operation in the

16 ga. copper covered steel wire (uninsulated) is best for

downposition may benecessary for reception of the very

both the antenna and the down lead. A lightening

weak signals since the noise limiter suppresses all low-

arrestor

should be connected to the down lead for protection
storm

damage.

design refer to
American

For
'A.

additional

information

against

er level signals.

on antenna

REC / STBY

R. R. L. Antenna Book" published by

antenna handbooks currently

The receiver may be silenced by moving

this slide switch to the STBY position witiout

Radio Relay League, or to any of the many other

actually

turning off power to the nrbes. Switching back to tfie REC

available.

position instantly returns tlle receiver to normal operaConnect the down lead from the antenna to the #2 terminal on the rear of the receiver

tion without warTn-up or retuning.

and connect the #l termi-

This jack provides aconnectionforheadphones

nal to a good earth ground such as a water pipe. Plug the

PHONE

power

(50 to 1000 ohms) which automatically silences tlre inter-

cord into a standard

receptacle

providing

ff7

VAC

power.

nal speaker.

2

t

,l

signals other than CW type).

of short wave

signals. The antenna should be mounted away from
trees,

ceiver for proper reception (Note: settings in the lov/er

for distance re-

outside antenna should be as high as practical

lines,

contains no modulation and must be modulated in the re-

is self-contained,

The Volume control functions as usual to

vary the volume at tie headphones.

S E T T U N I N GC A P A C I T O R
FULLY CLOSEO

L O O PC O R D

S E T T U N I N GC A P A C I T O R
FULLY CLOSEO

FAST E

S P R I N GH E R E

FASTE
G'

3_LooP
coRD3_t/2
TURt{SAROUNOSHAFT

LooPcoRD 2-t/2-''
T U R N S A R O U N DS H A F T

M A I NT U N I N GD I A LC O R D

B A N DS P R E A DD I A LC O R D
( R E A RV I E I Y )

(REAR VIEIV)

Fig. I

Dial Stringing Diagram

,ffit

s

---

c3
2-25

f3-

I

I
){
I
lc24

7

I

reov i

c4
4-40

L--

R7
looK

c22 L
.olptI

R2
t.5K :
g.F.o.

c5
4-40

R22
IK
c6
4-40

c27

I

30

c7
220

"/ sw4
.{

I

VIB

lz,eCuea
clo
t.o
R3
roo
R4
47K

ct5
.OO5Pf

V A L U E SA R E I N O H M SA I / 2 W A T TU N L E S S
ALL RESISTOR
O T H E R W I SSEP E C I F I E D ,
A L L C A P A C I T O RV A L U E SA R E I N M I C R O M I C R O F A R AU
DN
SL E S SO T H E R W I S ES P E C I F I E D .

oN B.F.O.

{as
I= 470

s
v2

V3
I2AV6

I28A6

V4
6AQ5A

TI

I
l
rC
t28
+7ovj

I c26
I-. o t p t

R24

o, sw 3 IOOK
.1 ST8Y.

I=

JI
PHONE

R23
4.7K

REc.

Rll

2.2M

4
8 . F . OC. O N T

cRl
c38
r t . o o 5 l E O3 0 0 4

Rt9

250 stv
clD
40pl
350v

crc
lOpf
350V

DX-75

/ii-\

ey/

,ri-3-l

t'_J

cs@

.t@

,-.@
.o@

15@
L6@

uz (O
L8@

o

Fig. 2

Chassis Layout Diagram

cq@
cs@
ceO

cu@
crz@
gs@
qq@

*
A L I C ; N M E N T I N S T I T I J C ' fI O N S

Equiptnr:nt rcquirccl :

RF Alig'nmcnt (con't.)

l.

Oscilloscopc with calibratcd vcrtical

2,

RF Signal gcncrator- capablc of:
a,

Z.

Final A-lig'nrncnt
ln t-lrc following

Oprcratiol fronr 455 KC to 30 MC

b. Attenuation
c.

scalc

ilicd

proccdurc,

(ltJ/u ntoclulat-ctl) is {cd into thc

frcqucncy

antenna tcrminal.

below lpv output

Modulation at I KC wich variablc

modula-

Thc antcnna and local oscil-

Iator tuncd circuits

tron pcrccnt.rges

rccovcrcd

a signal of thc spcc-

audio,

arc

adjustcd for

always adjusting

maximum

thc oscillator

cornlxrncnts first.
IF Alignnrent
1.

Looscly couplc a 455 KC, 50/u modulatcct signal
into thc antenna temrinals

(Bancl Sclector

Iland

in po-

sition #l)
2.

Corulcct oscilloscopc to spcaker tcrminals

3.

With signal gcncr.rtor:'sct to lowcstu.scablc signal levcl,

1rcak all IF- transfomrers

2

for nrexi-

rnunl recovcred audio.
4
RF Alignmcnt
l.

Prcliminary

Signal Frcq.
and
Dial Sctting

Adjust
for
Maximunr

600 KC
1 4 0 0K C

L5, LI
cll, c3

I,8 MC
4.3 MC

ctz, c4

5.0 MC
lr.0 Mc

L7, L3
c13, c5

lr.0 MC
3 0 . 0M C

L8, L4
c 14, c6

L6, L2

set up

a, Bcgi,ruringwith all tr-imnrer calrecitors

NOTE:

The atrovc adjustrncnts

tightly closcd, o1r:n thc trinrn)crs as fol-

ordcr

Iows:

caclt band, until propcr

C3

I /4 'I'urn

C4

3/4 Ttrn

C5

l/4 Tuln

C6

7/8 Turn

Crl

1/'2 1-urn

Clz

l/4'furn

Cl3

l/4'furn
l,z4 'furn

C 14

taincd.

b. llcginnirg $itlr ail slugs at top of fonn adjust as follotvs:
L2

l5 Turns

L3

22 Turns

L4

l5 Turns
30 Turns

L6

22 Turns

L7

30 Turns
'I'urns
15

L8
NO|E:

These settings are approximate and are NOT final-

7

shown,

anrl shoukl

should bc madc in tlrc

bc rcg.:atc-d scvcral

trackfurg and calibration

[inrcs

on

arc ob-

PARTS LIST

I ' T E MN O .

ITEM NO.

PART NO.

DESCRIPTION

DESCRIPTION

CAPACITORS (CONT.)

TUI]ES

22opt t20J, Z5lr 500V Ceramic

VI

6CL8A

-?

v2

128A6

t- 2)

V3

I2AV6

c33

NOT USED

V4

6AQsA

CAPACITORS

-350V-350V-150V
40 -20 -10 -4Oprfl350V

CI

Electrclytic
C2

PART NO.

I

00lpf t20fi ZSU 500V Ceramic

c34

.001pt !2ffi Z5U 500V Ceramic

r.?c

NOT USED

c36

.0lpf CMV ZsU 500VCeramic

c37

.()05 CMV ZsU 500V Ceramic

C3B

.005 GMV Z5U 5U0VCeramic

c39

40ttf./ 250Y Elcctroiytic

c40

.0lpf GMV Z5U 500V Ceratnic

.0lpf GMV Z5U 500VCerarnic
RESISTORS

2-2Spf Ceramic Trirnmer
4 -40pf Ceramic Trimmer
C5

4-40pf Ceramic Trimmer

RI

2M Variable

300-268- l8

C6

4-40pf Ceramic Trimmer

R2

l.5K Variable

rot -7 34 -6

C7

22Opttl\/o NPO 500V Ceramic

R3

l00ft tl0% l/2W Carbon

rra

Main Truring

3 0 1- 3 3 8- r

R4

47K tlj%

rro

Bandspread

3 0 1- 3 3 8- 2

t(5

3 . 3 M 1 1 0 %1 / 2 W C a r b o n

cr0

l.Opf t10/6 500V Composition

R6

lM t10% 1/2W Carbon

cll

/ - luuill ueramlc I rlmmer

R7

l00K tt0% 1/2W Carbon

CT2

4-4opf Ceramic Trimmer

R8

4.7K !10% I/2W Carlrcn

c13

4-4opf Ceramic Trimmer

R9

4700 tl0% l/2W Carbon

c14

4-4Opf Ceramic Trimmer

RIO

27in 1l0t; l/2W Carbon

cl5

.005uf GMV Z5U 500V Ceramic

Rtl

2.2M tl0T 1/2W Carbon

c16

Bzpf - l0!i N750 600V Ceramic

R12

47K t10% l/2W Carbon

c17

.Olpf GMV Z5U 500VCeramic

Rl3

47OK !I}a/(. t/2W Carbon

cl8

560pf t5lo 125V Polystyrene

R14

10M tl0% I/2W Carbon

cl9

1800pf15% 125V Polystyrene

Rl5

270K !10% I,/2W Carbon

c20

3900pf t5[

R16

470K !1070 l/2W Calllon

rtt

.0lpf CMV ZSU 500VCcramic

11r7

47Gt lI0To I/2W Caitx>n

c22

.0lpf GMV ZSU 500V Ceramic

R18

l&A tlO% i/2W Carbon

c23

.Olpf GMV Z5U 500VCeramic

Rl9

25A1!n% sW W.W.

c24

SEET3

R20

lK 110% l/2W Carbon

a)E

SEET3

R2l

4.7K !rO% l/ZW Carbon

c26

.0lpf GMV ZsU 500V Ceramic

a),

rK tl0% l/ZW Carbn

c27

R23

4.7K ! l07o I/2W Carbon

c28

30pf t5% NPO 500V Ceram.ic
'T4
SEE

R24

i00Ktl0% r/2W Carbn

c29

SEE T4

c30

30pf t57" NPO 500V Ceramic

1

l25V Polystyrene

I

l/2W Carbon

PARTS LIST (CON'T.)

ITEM NO.

DESCRIPTION

TRANSFORMERS

TI

Power Traasformer

lz

Outprt Transformer

.r?

T4

IF 455KC
IF 455KC

DESCRIPTION

ITEM NO.

PART NO.

PART NO.

MISCELLANEOUS

500-685
301-335

MI

Dial Light

#1813

M2

Dial Light

#1813

1655-6
1655-6

CRl

Diode 400PIV 500 MA.

ED-3004

cR2

Diode 400 PM00

ED-3004

J1

Phone Jack

I6-2

SPK T

Speaker

14826

COILS

MA.

Cabinet

600-r73-3

RF Band #l

301-340

Panel (Front)

5W-787

L2

RF Band #2

301-34l

Panel (Back)

soo-629-2

LJ

RF Band #3

30L-342

Knob (Bandspread -Tuning) 27OO2- L

L4

RF Band #4

30r-343

Knob (Band-Volume)

27OO2P-1

L5

Osc, Band #l

Knob (BFO)

26600P-r

L6

Osc. Band #2

30r-344
301-345

Dial Glass

301-336

L7

Osc. Band #3

30i -346

Feet

r00-435-1l

L8

Osc. Band #4

30r-347

LI

SWITCHES

swl

Power Switch

300-268- 18

(On Volume Control)

sw2
sw3
sw4

ANL (On - Off)

ss-32

STBY-REC

SS.32
LOr-734-6

BFO Switch
(On BFO Control)

sw5

Band Switch

301-339

9



---

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