National radio Ncx-5 User manual

37

WASHINGTON

STREET •

MELROSE,

MASSACHUSETTS

NCX-5

TRANSCEIVER

-

You

now

own

a

product

manufactured

by

one

of

the

world's

oldest

and

most

highly

respected

manufacturers

of

qual.ity

communications

equipment.

National

has

manufactured

superb

communications

devices

for

nearly

half

a

century.

Our

experience

is

unequaled.

More

than

75

per

cent

of

our

highly

skilled

test

and

assembly

people

have

been

with

us

for

more

than

25

years

-

an

astonishing

record

in

the

relatively

young

electronics

industry.

Our

people

know

their

business

...

take

pride

in

their

fine

workmanship

-

workmanship

so

outstanding

that

many

National

receivers

purchased

over

30

years

ago

are

still

in

daily

use.

We

manufacture

most

of

the

components

used

in

our

equip-

ment

...

and,

in

fact,

National

has

been

a

prime

supplier

of

electronic

components

to

other

important

electronic

manufacturers

and

government

agencies

for

many

years.

As

a

result,

we

enjoy

unusual

control

of

component

part

quality.

We

strongly

recommend

that

you

carefully

study

the

in-

struction

manual

before

attempting

to

use

your

new

equip-

ment.

We

C~re

sure

.

you

will

find

that

maximum

perfor-

mance

will

be

achieved

with

complete

understanding

of

its

controls

and

operating

features.

Your

new

National

equipment

has

undergone

an

intense

series

of

rigio

quality

control

tests.

However,

as

with

any

complex

electronic

equipment,

it

is

possible

that

a

defect

may

appear

as

a

result

of

rough

handling

during

shipment

or

through

circumstances

beyond

our

immediate

control.

For

this

reason,

we

suggest

that

you

inspect

your

new

equipment

for

such

damage

as

soon

as

it

is

unpacked.

In

all

cases

of

in-transit

damage

a

claim

must

be

filed

against

the

carrier.

The

component

parts

of

this

equipment

(exclusive

of

va-

cuum

tubes

and

transistors)

are

guaranteed

to

be

free

from

defective

material

and

workmanship

,

and

repair

or

replace-

ment

will

be

made

on

any

part

found

to

be

defective

upon

examination,

provided

that

the

which

has

been

subjected

to

misuse,

neglect,

accident,

improp

er

installations,

or

use

in

violation

of

instructions

furnished

by

us.

Nor

does

it

extend

to

units

which

have

been

repaired

or

altered

outside

of

our

factory

or

its

authorized

agencies,

nor

to

units

where

the

serial

number

has

been

removed

or

defaced.

Should

your

new

National

equipment

require

servicing

please

do

one

of

the

following

,

whichever

is

most

con-

venient:

1.

Return

it

to

the

dealer

from

whom

you

purchased

it.

2.

Bring

it

to

one

of

our

authorized

service

agencies

.

3.

Write

to

the

Service

Manager,

National

Radio

Company,

Inc.,

37

Washington

Street,

Melrose

,

Mass

.

and

describe

the

difficulty.

State

type

of

unit

and

serial

number.

De-

scribe

as

completely

as

possible

the

apparent

defect.

If

we

feel

that

the

unit

should

be

returned

to

the

fac-

tory

we

will

give

you

written

authorization

to

ship

the

unit

to

us.

Notify

us

that

you

are

returning

the

unit

and

ship

prepaid

and

fully

insured

in

the

original

specially

designed

shipping

carton.

Your

unit

will

receive

prompt

and

careful

attention.

If,

in

our

judgment

the

unit

is

indeed

defective,

repair

or

re-

placement

will

be

made

at

no

cost

to

you

if

the

unit

is

returned

within

90

days

after

date

of

original

purchase.

Should

the

unit

be

returned

to

us

after

90

days

from

date

of

purchase

but

before

365

days

have

elapsed,

again,

if

in

our

judgment

the

unit

is

i

ndeed

defective,

Nationa

l

Radio

Company

will

provide

a

replacement

of

any

such

defective

part

(except

vacuum

tubes

or

transistors).

If

you

wish

us

to

install

the

part,

you

will

be

billed

only

for

labor

costs

involved.

At

the

end

of

one

year,

after

expiration

of

guarantee,

service

will

be

billed

to

you

at

cost

of

parts

and

labor

only.

unit

is

delivered

to

your

dealer,

authorized

service

agency

or

to

the

company,

pursuant

to

the

instructions

below,

within

one

year

from

the

date

of

sale

to

original

purchaser

.

On

units

returned

during

the

initial

90

day

period,

National

Radio

Company,

Inc.

will

absorb

the

labor

cost

of

installation

;

for

the

remainder

of

the

guarantee

period

the

customer

w~l

be

charged

for

such

cost.

The

enclosed

guarantee

card

must

be

returned

to

National

Radio

Company,

Inc.,

within

ten

days

from

date

of

purchase

in

order

to

validate

the

guarantee

.

Naturally,

this

guarantee

does

not

extend

to

any

product

NATIONAL

ONE

YEAR

GUARANTEE

This

extended

guarantee

super-

sedes

all

of

National

Radio

Company,

Inc.

and

is

in

lieu

of

all

other

warranties

expressed

or

im-

plied.

Damages

arising

out

of

a

breach

of

this

guarantee

are

limited

to

repair

or

replace-

ment

of

the

defective

part

as

stated

above.

We

naturally

re-

serve

the

right

to

change

or

improve

our

products

without

imposing

any

obli.gation

upon

ourselves

to

so

modify

pro-

ducts

previously

manufactured.

Your

new

National

Radio

Com-

pany

equipment

is

the

finest

of

its

type.

It

was

sk •

designed,

carefully

tured

and

thorou

We

are

confident

choice

of

our

r I

result

in

many

ears

of

plea-

sure

.

INDEX

Page

SECTION

1

GENERAL

DESCRIPTION. . . . . . . .... ...... .... ........ .... .... ...... . 2

SECTION

2 INSTALLATION

......................

........

.

.............

.

....

.

....

3

2.1 Power Supplies

2.2

Mobile

Mounting

2.3

Microphone

Connections

2.4

Mobile

Speaker

Inst

allation

2.5 Auxiliary

Relay

Control

Terminals

SECTION

3

OPERATION.

...

. .

..............

...

........

. .. .

....................

5

3.1

Tuning

Procedures

3.2

Detailed

Use

of

the

Individual

Controls

SECTION

4

THEORY

OF

OPERATION

......

....

.....

...

.

....

.

..

. . ..

...

.

....

.....

11

4.1

General

4.2

The

Transmitter

4.3

The

Receiver

4.4

The

VOX

Circuits

4.5

The

Function

Switches

4.6

Relay

Functions

SECTION

5 ALIGNMENT. . . . . . ...... .... .. .. .... ........ .. .. ...... .... .... .. .... 15

5.1

Equipment

Required

5.2

Initial

Control

Settings

5.3

IF

Alignment

Procedure

5.4

Balanced

Modulator

Adjustment

5.5

Carrier

Oscillator

Setting

5.6

Transmitter

Bandpass

Tuning

5.7 Receiver Bandpass

Tuning

5.8

VFO

Frequency

Alignment

5.9

VFO

Linearit

y Adjustment

5.10

VFO

Sideband

Switching

Adjustment

5.11

Temperature

Compensating Adjustment

5.12

Transmit

Mixer

and

Driver

Alignment

5.

13

Final

Amplifier Preliminary Adjustment

(10

Meter

)

5.14 Neutralizing

Capacitor

5.15

Final

Amplifier

Preliminar

y Adjustment

(80-15

Meter

)

5.16

Final

Amplifier

Tuning

Checks

5.17 Local Oscillator Crystal

Adjustment

5.18 Parasitic

Check

5.19

Carrier

Suppression,

Sideband

Suppression,

Modulation,

an

d

ALC

Checks

5.20

Transmit-Receive

Frequency

Check

5.21

LSB-USB

Switching Check

5.22 Switching

Tests

5.23 Transceive

Vernier

5.24 Anti-

VOX

Check

5.25

VFO

Jack

SECTION

6

PARTS

LIST. . . . . . . ... .. ...... .... .... .. .. .... .... ...... .. .... ...... . 24

SECTION

7

VOLTAGE

AND

RESISTANCE

MEASUREMENTS

.....................

26

1

SECTION

1

GENERAL

DESCRIPTION

The

NCX-5

is

a five

band

high-performance

transceiver for

the

80, 40, 20, 15,

and

10

meter

amateur

bands,

intended

for use in fixed

home

in-

stallations, as well as for portable

and

mobile appli-

cation.

The

NCX-5

provides choice

of

SSB,

CW,

or

AM

operation

with unusually

accurate

dial calibration

and

high

frequency stability, together

with

operating

features

in

all

three

modes normally available only

with separate receiver-transmitter combinations.

A

NATIONAL

8-pole crystal lattice filter

with

a 6

to

60 db. shape factor

of

1.7:1

and

a

bandwidth

of

2.8

Kc

@ 6 db. provides sideband suppression

and

receiver selectivity previously

found

only in

commer-

cial communications

equipment.

DIGITAL

READOUT

from

a

counter

type dis-

play provides easy

adjustment

and

resettability.

The

SOLID

STATE

VFO

eliminates

the

drastic

initial

warm-up

drift

so characteristic

of

tube

type

VFO's.

The

stability

of

this

VFO,

together

with

crystal controlled high frequency oscillators, results

in

a remarkably stable double conversion receiver

and

transmitter combination.

A

TRANSCEIVE

VERNIER

control

in

the

NCX-5

allows

independent

adjustment

of

the

receiver

frequency

from

that

of

the

·transmitter

section

over

a

range

of

-+-

5

Kc

from

the

displayed

(transmitter

)

frequency.

SIDEBAND

SELECTION

is

possible

at

the

flick

of

a switch; (USB-LSB)

without

retuning

the

VFO.

The

operator

may

instantly select the opposite side-

2

band

to reduce

QRM

or

to make

accurate

SSB sup-

pression checks

with

the

calibrated S-meter.

ALC

(

automatic

le\·el control)

is

incorporated

in

the

NCX-5.

Effecti\·e talk power

is

increased

and

microphone

gain

and

speech loudness

are

made

non-

critical by this system.

The

10 db. range

of

the

ALC

circuit

in

the

NCX-5

prevents "flat

topping"

and

splatter.

An

ALC

INPUT

JACK

is

provided

on

the

NCX-5

for use

with

the

NCL-2000 2

Kw

linear

amplifier for control

of

the

NCX-5

by

the

ALC

voltage from

the

NCL-2000.

Choice

of

VOX-PTT-MANUAL

operation

is

performed from

the

front

panel

when

operating

AM

or

SSB.

BREAK-1:\f

GRID

BLOCK

KEYING

for

CW

operation

accomplishes

automatic

transmit-receive

switching

at

the

tap

of

a key.

Two

detectors are

incorporated

in

the

NCX-5:

a

product

detector for SSB,

CW,

or

"exalted

carrier

AM,"

and

an

excellent diode

detector

for

AM

opera-

tion.

A

VFO

INPUT

JACK

on

the

rear

apron

con-

nects to the VX-501 optional

VFO

console.

The

VX-501, when used

with

the

NCX-5,

pro\·ides com-

pletely

independent

control

of

transmit

and

receive

frequencies, as well as transceive control

by

either

the

VX-50

1

or

the

NCX-5.

Besides its \

·Fo

function,

the

VX-

5

01

provides for crystal control

oi

!he

:\CX-5

transmit, receive

or

transceive frequencie;;.

SECTION 2

INSTALLATION

2.1

POWER

SUPPLIES:

The

NCX-5

transceiver

may

be used with

eith

er

the

matching

NCX-A

115/230 volt A.C.

or

the

NCX

-D 12 volt D.C.

power

supplies.

We

strongly

recommend use

of

the

National Power Supplies de-

signed for

the

NCX-5

because

of

their

extremely

"stiff" voltage regulation

and

superior filtering.

NCX-A

power supplies

with

serial numbers be-

ginning with

73

or

higher

are

designed for operation

with

the

NCX-5

transceiver.

NCX-A

power supplies

with serial numbers beginning with 44, 49, 57, 63, 69,

or

72

must be modified before use with the

NCX-5

transceiver.

This

modification

may

be easily

made

by

connecting a 660

ohm

10

watt

resistor in parallel with

the

two

330

ohm

10

watt

resistors R-5

and

R-6

in

the

NCX-A

power suppl

y.

A partial schematic

of

the

revised s

upply

is shown on Figure #

1.

2.2 MOBILE MOUNTING:

A

mounting

bracket is supplied as s

tandard

equipment with

the

NCX-5

transceiver.

For

mobile

operation, this bracket should

be

mounted

under

the

automobile dashboard with

two#

10, # 12,

or

1/4

x 20

screws.

For

maximum

stability, these screws should be

located as

far

apart

as possible

in

the mobile

mount-

ing

bracket. A

pair

of large threaded knobs hold

the

transceiver directly

to

the

bracket. These knobs per-

mit

rapid

installation

or

removal

of

the

transceiver

from the

mount.

Mobile operation usually results in

considerable

vibrat

ion

and

shock.

For

maximum

fre-

quency stability

of

the

NCX-5

transceiver,

it

is

im-

por

t

ant

that

all mounting screws used

to

hold

the

cabinet

to

the

chassis

and

panel

assembly be

in

place

and

firmly tightened.

In

mobile use,

the

rubber

feet

may be removed from

the

bottom

of

the

NCX-5

.

2.3

MICROPHONE CONNECTI

ONS:

'rhe

microphone

input

of

the

NCX-5

is

equipped

with a three circuit jack providing a

ground

on

the

main

shank

of

the

three circuit plug.

The

audio

out-

put

of

a high-impedance ceramic

or

dynamic micro-

phone

(a

crystal microphone

may

be used,

but

is

not

recommended for mobile op

erat

i

on)

should

be

con-

nected

to

the

ring

of

the

three circuit

jack

.

If

the

microphone is equipped with a push-to-talk button,

the

push-

to-ta

lk

button

should be

so

wired

that

the

3

tip

of

the

microphone plug is connected

to

the

grounded

shank

of

the

plug

when

the

push-to~talk

button

is pressed.

The

microphone push-

to-ta

lk

button

is connected

to

the

-40

volt bias.

- CAUTI

ON-

Accidental interchange

of

the

wmng

on

the

microphone plug will result

in

application of

-40

volts

to

the

microphone cartridge, which

may

damage

the

microphone.

'rhe

microphone

input

jack

of

the

NCX-5

is

equipped with a grounding contact so

that

no

mod-

ulat

i

on

of

the

transceiver is possible when

the

micro-

phone plug is removed.

Microp

hone connections

are

illustrated in figure No.

1.

We

recommend the use

of

a good quality, wide-range microphone, since all neces-

sary restriction

of

audio

bandwidth

is accomplished

in

the

NCX

-5 crys

tal

lattice filter.

The

P'I'T

circuit

of

the

microphone should be modified

to

permit

VOX

operat

i

on

without depressing

the

PTT

button.

This

may

be done by bending

one

of

the

shorting contacts

inside

the

microphone

so

that

it

does

not

short

the

microphone cartridge terminals

when

the

button

is

released.

2.4

MOBILE SPEAKER INSTALLATION:

When

the

NCX-5

is installed

in

an

automobile

for use

with

the

NCX-D

supply,

it

will usua

ll

y be

most convenient

to

use

the

speaker

of

the

regular

automobile broadcast radio.

Two

leads should be

brought

out

of

the

12

terminal Jones plug

at

the

rear

of

the

NCX-5

(pins 5

and

7)

and

connected

to

the

speaker

thro

u

gh

a

DPDT

switch

mounted

under

the

dash

to

allow choice

of

speaker operation

with

either

the

NCX-5

or

the

standar

d broadcast radio.

2.5

AUXILIARY

RELAY

CONTROL TERMINALS:

A

pair

of

SPST

relay terminals

rated

at

3 amperes

current

capacity is provided

at

the

rear

of

the

NCX-5

to

allow control of accessory

equipment

such

as

the

NCL-2000 amplifier.

'rerminals

are

open

during

re-

ceive, closed

during

transmit.

.

3

INSTALLATION

FIGURE

1

. .

5 4

.

7

=

REV

I

S1

0 N

FOR

USE

WITH

NCX-5

TRANSCEIV

ER

4

I POWER SWITCH

~

POWER SWITCH

4

~:.60YYOLOLTT

BIAS

o

6UA

HEATER

5

SPEAKER

GROUN~

A

6 COUUON GROUND

7

SPEAKER

~

+280YOLT0200UA

+700YOLTo300UA

II

I

...l. 7

6 5 4

I I I

3 2

I I

POWER

CONNE

CTIONS

MICROPHONE CONNECT.ONS

SECTION

3

OPERATION

3.1 TUNING

PROCEDURES:

3.1.1

PRELIMINARY

ADJUSTMENT

-CAUTION-

BEFORE

ATTEMPTING

TO

OPERATE

THE

NCX-5 TRANSCEIVER,

THE

FOLLOWING

PRELIMINARY

CONNECTIONS

SHOULD

BE

MADE: A SUITABLE ANTENNA

OR

DUMMY

LOAD

PRESENTING

40

TO

60

OHMS

RE-

SISTIVE

LOAD IMPEDANCE

SHOULD

BE

CONNECTED

TO

THE

ANTENNA

TERMI-

NALS, A

PROPER

POWER

CABLE

SHOULD

BE

CONNECTED

FROM

THE

POWER

SUPPLY

TO

THE

NCX-5

TRANSCEIVER

, AND A

MICROPHONE

OR

KEY

SHO

U

LD

BE

CON-

NECTED

TO

THE

APPROPRIATE

INP

UT

JACKS.

THE

FUNCTION

SWITCH

SHOULD

REMAIN

IN

THE

OFF

POSITION

WHILE

THESE

CONNECTIONS

ARE

BEING

MADE.

1.

Set front panel controls as follows:

MIC

GAIN fully ccw (counterclockwise)

TRANSCEIVE

VERNIER

in

OFF

posi-

tion (pushed in)

RF

GAIN

fully cw (clockwise)

AUDIO

GAIN

at

9 o'clock

BAND and

MAIN

TUNING

to desired band

and

frequency

PA

TUNE,

PA

LOAD

, and

EXCITER

TUNE

fully ccw

VOX-PTT

switch in either position

MOX-OFF

switch:

OFF

SIDEBAND switch on desired sideband

(usually LSB on the 80

and

40 meter

bands, and USB

on

20,

15,

and

10

meter

bands).

5

2.

VOX

GAIN,

VOX

DELAY, and

MIC

GAIN inside top cover should be set fully

ccw, and

CARRIER

BALANCE

at

12

o'clock.

3. BIAS adjust on rear panel should be set

at

12

o'clock.

3.1.2

RECEIVER

TUNE-UP

(SSB)

1.

Turn

FUNCTION

switch from

OFF

to

SSB.

After several seconds warm-up,

the

NCX-5 transmit-receive relay should close

with

an

audible click.

The

NCX-5

is

now

in a receive condition on the selected band

and

frequency.

2.

Adjust PA

TUNE

and

EXCITER

TUNE

for maximum S-meter reading

or

background

noi

se.

This adjustment automatically sets

up

approximate transmit tuning since these con-

trols are common for both transmitter

and

rece1ver.

3.

Adjust

AUDIO

GAIN for comfortable listen-

ing level.

3.1.3

TRANSMITTER

TUNE-UP

(SSB)

-CAU

T

ION

-

DO

NOT

PROLONG

TUNE

-

UP

PROCE-

DURES

MORE

THAN

30 SECONDS

AT

A

TIME

IN

ORDER

TO

PREVENT

UNNECESSARY

OVERHEATING

OF

COMPONENTS

DURING

OUT-OF-RESONANCE

CONDIT

IONS.

AFTER

EXPERIENCE

IS GAINED,

TUNE-UP

MAY BE

ACCOMPLISHED

IN

A

MATTER

OF

A FEW

SECONDS.

1.

Turn

FUNCTION

switch to

TUNE

and

adjust

EXC

I

TER

TUNE

for maximum

meter reading.

2.

Adjust PA

TUNE

for minimum meter read-

ing (dip) indicating proper tuning

of

the

Pi network. Slowly rotate the PA LOAD con-

trol cw

and

dip

meter reading with P.A.

TUNE

control until meter reads 300 MA.

3:

Return

FUNCTION

switch

to

SSB.

Push

the

MOX-OFF

switch

to

the

MOX

posi-

tion,

and

carefully rotate the

CARRIER

BALANCE control inside the top cover for

minimum meter reading.

NOTE:

IF

THIS

IS

THE

FIRST

TIME

THAT

THE

NCX-5 HAS BEEN PLACED

IN

OPERATION,

THE

REAR

PANEL BIAS

CONTROL

SHOULD

BE

ADJUSTED.

THE

NCX-5

IS

IN

TRANSMIT

WITH

THE

MOX-OFF

SWITCH

IN

THE

MOX

POSITION.

THE

REAR

PANEL BIAS

CONTROL

SHOULD

BE

ADJUSTED

UNTIL

THE

METER

READS

BETWEEN

50 AND 60 MA.

Return

the

NCX-5

to

the

receive con-

dition

(MOX

switch

OFF).

3.1.4

MOX

OPERATION

1.

The

NCX-5 transceiver will now operate in

both

the

transmit

and

receive modes using

the

MOX-OFF

switch for transmit-receive

control.

3.

1.5

VOX

OPERATION

1.

Place

the

MOX-OFF

switch

in

the

OFF

position.

2.

Place front panel

VOX-PTT

switch

to

VOX.

3.

Turn

receiver

AUDIO

GAIN

control (on

the front panel)

and

VOX

DELAY control

(inside the top cover) completely ccw.

4. Rotate the

VOX

GAIN

control (inside the

top cover) until the relay just trips reliably

while speaking into

the

microphone. Adjust

VOX

DELAY until

VOX

relay holds

in

for

the desired time after speaking. These

ad-

justments interact

to

a small degree,

and

it

may be necessary to repeat all adjustments

once

or

twice

to

optimize results.

Mobile

VOX

operation

is

quite easy

and practical,

but

VOX

GAIN

and

MIC

GAIN

should be adjusted for maximum

close-talking

to

prevent car

and

wind noises

from tripping

the

relay.

3.1.6

PTT

OPERATION

1.

Place

the

MOX-OFF

switch in the

OFF

position.

2.

Place

the

VOX-PTT

switch

to

PTT.

3. Connect a suitable push-to-talk switch as

shown

in

figure No.

1.

The

NCX-5 will op-

erate in both

the

transmit

and

receive modes

6

by control from the external push-to-talk

switch.

The

VOX

DELAY control remains

connected

in

the

PTT

mode

and

may be

adjusted for fast or slow return to receive

when the push-to-talk button

is

released.

3.1

.7

CW

OPERATION

1.

It

is

assumed

that

the NCX-5 has been set

up

for

SSB

operation

and

that

it

is

now de-

sired

to

operate CW.

2.

Insert key plug in rear panel jack.

3.

Turn

FUNCTION

switch

to

TUNE

and

adjust transmitter as for SSB operation.

4.

Turn

FUNCTION

switch

to

CW, depress

key,

and

adjust

CARRIER

BALANCE con-

trol (inside

top

cover) until meter reads

300 rna.

5.

The

NCX-5

is

now tuned for

CW

operation

and

is

ready for full break-in operation.

When

the

key

is

depressed

to

start sending,

the

VOX

relay will hold

in

until

the

oper-

ator stops sending,

and

then will automati-

cally switch to receive.

By

adjusting the

VOX

DELAY control (inside the

top

cover),

the

operator may set

the

"hold-in" relay time

to

his liking.

3.1.8

AM

OPERATION

1.

It

is

asumed

that

the

NCX-5 has been set

up

for SSB operation

and

that

it

is

desired

to

operate AM.

2.

Either

MOX,

VOX,

or

PTT

operation

should be selected.

3.

Turn

FUNCTION

switch

to

TUNE,

and

adjust transmitter as for SSB operation.

4.

Turn

FUNCTION

switch

to

AM, press

MOX-OFF

switch

to

MOX,

and

adjust

CARRIER

BALANCE until meter reads

150 rna.

5. Advance

MIC

GAIN

until meter just flickers

on voice peaks.

6.

The

NCX-5

is

now adjusted for

AM

opera-

tion,

and

the

AM

detector is automatically

in use.

3.2

DETAILED

USE

OF

THE

INDIVIDUAL

CONTROLS:

The

operating instructions in Section

3.1

of this

manual enable rapid setup of

the

NCX-5 for SSB,

AM,

or

CW

transmission. Careful study of

the

following paragraphs will help you get

the

best

performance from your NCX-5 transceiver.

3.2.1

MAIN

TUNING

CONTROL

AND

DIGITAL

DIAL

READOUT

NCX-6

T

R.

A N

The

NCX-5 transceiver incorporates a digital-

type direct frequency readout

to

allow frequency

adjustment

to

1

Kc

without interpolation between

divisions.

The

VFO

is accurate to 1 Kc,

and

it

is

read by adding the frequency

in

kilocycles shown

on

the counter dial

to

the frequency

in

megacycles shown

on

the

BANDswitch. With

the

BANDswitch

in

the

14.0

Me

position,

the

frequency as shown

in

the

illustration above

is

14.321 Me.

If

the

BANDswitch

were

in

the

3.5

Me

position, for example, the above

frequency would be 3.5

Me

plus

321

Kc,

or

3.821 Me.

To

provide even greater resettability, the NCX-5

readout incorporates a fourth window, as shown

above, calibrated in ten one-hundred-cycle divisions.

The

illustration above actually indicates

that

321

Kc

plus 200 cycles (321.2

Kc)

should be added to the

BANDswitch frequency.

3.2.2

DIAL

SET

The

dial

of

the

NCX-5

may

be adjusted

to

exact

frequency, such as a 100

Kc

marker from the op-

tional plug-in XCU-27 calibrator, by tuning

to

the

marker

frequency in the receiver

and

then

by pulling

out the main tuning knob of the NCX-5

and

turning

the knob until the dial reading corresponds to the

known marker frequency.

3.2.3

THE

FUNCTION

SWITCH

Note the various interlocking features

of

the

FUNCTION

switch.

In

the

SSB

or

AM

positions of

the

FUNCTION

switch, either

VOX,

MOX,

or

PTT

operation may

be

used (see paragraphs 3.2.8

and

3.2.9).

The

rear

p~nel

key_

j~ck

is

disconnected

in

the SSB

or

AM

positions, thus allowing a key to be

left plugged

into

the NCX-5

at

all times. Accidental

closing

of

the key will

not

trip

the

unit

to transmit

if the

·FUNCTION

switch is

in

either

the

SSB

or

AM

position.

In

the SSB position,

the

product de-

7

tector IS m use,

and

in

the

AM

position, the diode

detector

is

selected. Bias is applied

to

the carrier

oscillator during AM receiving periods, thus silencing

the beat frequency oscillator

of

the

receiver.

If

the front panel

FUNCTION

switch is

in

the

CW

position,

the

rear panel key jack is connected for

automatic break-in operation. At the same time, the

plate

of

the microphone preamplifier

is

grounded

to

prevent accidental modulation

of

the transmitted

signal by a microphone connected

to

the NCX-5.

During

CW

operation, the

VOX-PT!

switch

can

be

in

either the

VOX

or

PTT

positions without any

effect

on

the operation

of

the

transceiver.

The

slight

audio "beep" which may be

heard

from the loud-

speaker

at

the

beginning of each keying cycle

is

the

result

of

the extremely fast attack time

of

the break-in

CW

circuit which eliminates "clipping"

the

first dot.

Finally,

in

the

TUNE

position

of

the

FUNC-

TION

switch, the keying circuit is internally

grounded, placing the NCX-5

in

transmit condition.

At

the

same time, one

of

the deflection electrodes

of

the 7360 balanced modulator

tube

is

grounded, un-

balancing the tube

and

providing more

than

normal

drive

to

the final amplifier for tune-up.

It

is im-

portant

to

note

that

if the

FUNCTION

switch

is

placed

in

the

TUNE

position,

and

an

antenna

is

connected to

the

NCX-5, full power transmission

of

a

CW

note will occur

and

can

cause unwanted

interference.

Tune-up

procedure should therefore be

limited

to

as short a time as possible.

3.2.4.

THE

PA

TUNE

AND PA

LOAD

CONTROLS

Adjustment

of

the

PA

!UNE

and

PA

LOAD

controls

is

interdependent.

For

normal tune-up, the

FUNCTION

switch

is

placed

in

the

TUNE

position.

The

EXCITER

TUNE

control

is

set for maximum

meter indication.

The

PA

TUNE

control

is

then set

for minimum indication, indicating resonance

of

the

Pi network.

For

a normal 40

to

60

ohm

resistive an-

tenna,

the

PA

LOAD

control should

be

rotated clock-

wise

to

increase the meter reading.

As

this is done,

there will be some interaction with

the

PA

TUNE

control,

and

it

will be necessary to slightly adjust PA

·

TUNE

for minimum meter indication.

As

the

PA

LOAD

control

is

advanced, the minimum meter read-

ing will increase. Proper loading for 200 watts peak

input

occurs

at

300 rna (marked

in

red

on

the meter

scale). This loading current should not be exceeded,

since the Pi network design is such

that

additional

power

input

from a 700 volt supply will not result

in

additional power output. Above 300 rna the efficiency

of

the NCX-5 final amplifier will

be

impaired,

and

no

further

output

will be obtained.

Proper

ope~ation

of

any linear final amplifier

depends

on

proper idling current adjustment

and

on

sufficient drive for adequate peak plate current during

an

off-resonance condition.

The

adjustment

of

the

bias setting

of

the NCX-5 final amplifier is discussed

in

paragraph

3.1.3. Assuming this setting has been

made

for

an

idling

current

between

50

and

60

rna,

it

should be possible

to

obtain a momentary maximum

off-resonance piate current

in

·excess

of

350

rna

when

the PA

TUNE

control is

rotated

away from

the

point

of minimum current.

If

700 volts

is

being properly

supplied

to

the plate circuit of the final amplifier,

and

the

EXCITER

TUNE

control

is

proper

ly

ad-

justed, this off-resonance

current

should exceed 350

rna.

If

this current

cannot

be achieved,

the

cause

should be found. Typical causes may include any of

the following: improper Bias setting, improper

EXCITER

TUNE

adjustment, low plate supply

voltage to

the

final amplifier under full load condi-

tions, low driver B+, defective final amplifier tubes

or driver tube,

or

improper alignment

of

the

exciter

stages resulting

in

low driving signal.

As

mentioned above, low plate supply voltage

to

the

final amplifier will frequently result

in

diffi-

culty

in

obtaining a suitable off-resonance current.

The

NCX-A

power supply is

rated

to deliver 700 volts

to

the

final amplifier with a 115 volt A.C. input.

The

NCX-D

power supply is

rated

to deliver 700 volts

to

the

plate circuit

of

the

final amplifier with a 14.0

volt

input

to

the power supply.

If

the A.C. line voltage

or

the

mobile battery supply voltage

is

low, the

power supply

output

wil

be

reduced.

Under

these

conditions,

an

off-resonance

plate

current

of

less

than

350 rna will probably occur.

This

will

not

impair

the

operation

of

the

NCX-5 transceiver, provided

that

the PA

LOAD

control is

not

adjusted for excessive

loading conditions.

In

no

event should

the

LOAD

control be advanced

so

that

the

plate

current

at

the

resonant

dip

exceeds

85%

of

the off-resonant plate

current, which is noted by momentarily

detuning

the

PA

TUNE

control.

In

many

instances

an

antenna

load

that

is outside

the 40

to

60

ohm

range

of

the

Pi network will be

used with

the

NCX-5. Antennas presenting this type

of impedance should,

if

at

all possible, be adjusted to

present a

proper

load

at

the

NCX-5

antenna

term-

nals.

This

can

be done through the use

of

matching

ne~works

and,

in

many instances, by simply tailoring

the length of

the

antenna

transmission line

to

modify.

its terminal impedance.

. Generally speaking, if the NCX-5 exhibits a

resonant

plate

current in

the

dip

in excess

of

300 rna

with

the

PA

LOAD

control rotated

to

its full counter-

clockwise position, the

antenna

load impedance

is

below 40 ohms.

If,

on

the

other

hand,

the

resonant

dip is still less

than

300 rna

with

the

PA

LOAD

con-

trol rotated

to

its full clockwise position,

the

antenna

load impedance

is

above 60 ohms.

It

is possible to

modify

the

Pi network

output

capacitors

of

the

NCX-5

to

take care of some misloading

in

these

directions.

With

the

PA

housing. removed, a group

of four

mica

capacitors will be seen just below the

BANDswitch

and

connected between

the

BAND-

switch

and

chassis. These capacitors, C-37 (3.5

Me),

8

C-38 (7

Me),

C-39 (14

Me),

and

C-182 (21

Me)

are, respectively, 1000, 470, 220,

and

220 pF.

They

appear

in parallel

with

the front

panel

PA

LOAD

control as shown

on

the

schematic

diagram

and

may

be altered to extend

the

range

of

the Pi network.

If

the

load impedance

is

too low, the capacitance should

be increased. A good quality silver mica capacitor

may be used for this purpose.

It

is

advisable

to

use

as large a case size

on

these capacitors as

can

be

obtained.

There

is of course some interaction of

tuning

between the

PA

LOAD

control

and

the

PA

TUNE

control.

If

load

matching

as described in

the

pre-

ceding

paragraph

is

attempted,

it

is possible

that

the

tuning

of

the

PA

TUNE

control will

be

shifted to

a point where this control will

no

longer cover

the

entire

amateur

band.

In

this event,

it

will

be

necessary

to

use external matching techniques.

It

is also possible

that

the

antenna

line will introduce

an

inductive

or

capacitive component

to

the

NCX-5

antenna

termi-

nals.

In

this event, there may be also a shift

of

the

PA

TUNE

control so

that

it

will

not

tune

over

the

entire amateur band. Again

it

will

be

necessary

to

alter

the

antenna

impedance by means

of

an

external

matching network

or

correction

of

the

antenna

diffi-

culties. SSB operation should

not

be

attempted

.unle~

the NCX-5 is properly matched

and

loaded because

severe distortion

can

result with

any

improperly

matched SSB transmitter

or

receiver.

3.2.5

CARRIER

BALANCE

CONTROL

During

the

tune-up

(with

the

FUNCTION

switch

in

the

TUNE

position), one deflection elec-

trode

of

the 7360 balanced

modulator

is

grounded,

creating complete carrier unbalance. Having accom-

plished proper transmitter tune-up,

it

is necessary

to

use the

CARRIER

BALANCE control

to

properly

set

up

the

NCX-5

transceiver for operation

on

SSB,

AM,

or

CW

operation.

For

SSB operation, the

NCX-5

is placed

in

a

transmit condition

either

by

the

push-to-talk

button

or

the

MOX-OFF

switch.

In

either

event,

the

MIC

GAIN

control should be

in

full ccw position

so

that

no audio modulation will occur.

The

CAR-

RIER

BALANCE control

is

then

adjusted for

minimum meter indication.

This

meter

reading should

be between

50

and

60 rna

if

the

BIAS control

is

properly adjusted.

When

the

CARRIER

BALANCE

control

is

properly set,

it

may be left

in

this position

for all subsequent SSB operation. A more precise indi-

cation

of

CARRIER

BALANCE control setting may

be obtained either by using

an

oscilloscope connected

to

the

antenna

line

or

by listening

to

the

carrier

on

a separate receiver.

With

proper carrier balance

and

tuning

of

the transceiver circuits, voltage

on

the

an-

tenna

line should

not

exceed 0.5 volts peak-to-peak

as indicated

on

the

oscilloscope.

For

AM

operation,

it

is

nec~3sary

to

adjust

the

CARRIER

BALANCE control

either

cw

or

ccw

from

the

balance

point

until

the

meter indicates a

final amplifier

current

of

150 rna.

This

corresponds to

approximately 100 watts

input

to

the

final amplifier,

thus assuring operation

of

the

tubes within their plate

dissipation rating.

Finally, for

CW

operation,

it

is

necessary

to

ad-

just

the

CARRIER

BALANCE control either

cw

or

ccw from its zero setting until a meter indication

of

300 rna is obtained.

This

assures

an

input

to

the

final

amplifier of 200 watts during key down transmit

conditions

of

CW

operation. Normal keying wave

forms approximate a

50%

duty cycle;

that

is, there

is

full

input

for

about

~

of

the

time

and

no power

for

the

remaining time.

Thus

the

time-averaged

input

to

the

final amplifier

is

still approximately 100 watts,

assuring conservative operation

of

the

final amplifier.

3.2.6

CALIBRATOR

CONTROLS

When

the

accessory

XCU-27

100

Kc

calibrator

is

plugged into

the

octal socket

on

the

rear

apron, 100

Kc

crystal markers are available for precise calibration

of

the

NCX-5.

The

calibrator

is

activated by means

of

a pull-push switch on

the

AUDIO

GAIN

control.

The

dial may

then

be

set by following

the

instructions

in

paragraph

3.2.2.

3.2.7

S-METER

ADJUSTMENT

Proper S-meter adjustment

of

the

NCX-5

is

ob-

tained by disconnecting

the

antenna

while the

NCX-5

is

set for SSB reception.

With

the

RF

GAIN

fully

clockwise (maximum gain),

the

S-meter

ad

justment

(in front right corner

of

chassis)

is

rotated

until the

meter indicates between 0

and

1

"S"

units.

3.2.8

VOX-PTT

SWITCH

AND

VOX

C.IRCUIT

ADJUSTMENTS

The

VOX-PTT

switch

may

be set

to

either

mode, depending

on

preference

and

availability

of

a push-to-talk button

on

the

microphone. Proper

microphone jack connections

are

illustrated

in

figure

No.

1.

Assuming

that

VOX

operation is selected,

the

operator will find

that

the

VOX

GAIN

and

VOX

DELAY

control settings

of

the

NCX-5 are remarkably

free from interaction.

The

extreme

VOX

sensitivity

available in the NCX-5 permits full anti-vox insertion

at

all times.

As

a result,

no

anti-vox control adjust-

ment

is required.

With

the

VOX

DELAY

control

fully ccw,

VOX

GAIN

control

is

advanced slowly

until

the

microphone just trips

the

NCX-5

to

transmit

with normal speech level. Mobile operation requires

close talk

to

the

microphone, since

the

high level of

road, wind,

and

motor

noises will otherwise

tend

to

accidentally

trip

the

VOX

circuit.

The

VOX

DELAY

control

is

then

adjusted for

the

desired release time.

It

should be further noted

that

PTT

and

CW

break-in operation are obtained through use of the

9

VOX

circuit. However,

the

VOX

GAIN

control will

have

no

effect

on

this operation

and

may

·be left in

any position. ·

The

VOX

DELAY

control is effective

on

both

PTT

and

CW

break-in operation

and

should

be adjusted

to

the

operator's liking for delay

at

the

end

of

the

transmission.

3.2.9

THE

MOX

-

OFF

SWITCH

The

MOX-OFF

switch

in

the

MOX

(manual

operation) position places the

NCX-5

in

the

transmit

mode, regardless of

the

position

of

the

VOX-PTT

switch

or

the

FUNCTION

switch.

This

position is

useful for

manual

operation when the microphone

is

not equipped with a

PTT

switch.

When

the

MOX-

OFF

switch is

returned

to

the

OFF

position,

VOX

or

PTT

operation

may

be selected by

the

VOX-PTT

switch.

3.2.10

TRANSCEIVE

VERNIER

CONTROL

The

TRANSCEIVE

VERNIER

control allows

± 5

Kc

separation

of

the

receive frequency from the

transmit frequency

of

the

NCX-5.

It

is

actuated by

pulling

the

control

out

and

rotating

the

knob to in-

crease

or

decrease receiver frequency.

The

transmit

frequency

of

the

NCX-5 remains unchanged

at

all

times-only

the receiver frequency

is

affected by

the

TRANSCEIVE

VERNIER.

The

NCX-5

TRANS-

CEIVE

VERNIER

will be

found

to be extremely

useful

in

AM

or

CW

QSO's, as well as

in

SSB net

operation.

It

allows

the

operator

to

tune

to

the

de-

sired

AM

or

CW

station with

the

VERNIER

control

pushed

OFF

, thus placing

the

transmit section

of

the

NCX-5

on

frequency.

Then

the

TRANSCEIVE

VERNIER

can

be

pulled

ON

to

offset receiver fre-

quency enough

to

allow

tuning

of

the

station

to

the

proper

part

of

the filter passband for best copy with-

out

"walking" of

the

transmit signal.

To

escape

QRM

during a

QSO

on

SSB,

the

TRANSCEIVE

VERNIER

can

be used to find a

clear channel.

Once

a clear channel is found,

the

NCX-5 receiver

is

placed back

on

frequency simply

by pushing

the

control

IN,

and

arrangements may

be

made

to QSY.

The

casual listener

may

also listen

to two adjacent

QSO's

by merely

turning

the

TRANSCEIVE

VERNIER

control

on

and

off

and

thereby instantly place

the

NCX-5

receiver

on

either

frequency.

3.2.11

MIC

GAIN

CONTROL

After

the

NCX-5

has been set

up

by proper

tuning

of

the

final amplifier

and

exciter stages

and

the

CARRIER

BALANCE control has been prop-

erly set for carrier balance,

the

MIC

GAIN

control

should

be

advanced until

the

meter

reads between

100

and

125 rna average on speech content from

the

microphone.

The

single sideband audio information

so

developed has a rapidly varying energy content

and

the

meter will rapidly fluctuate between

the

40

to 50 rna idling

current

and

the

100 to 125 rna average

meter

reading. Actual peak

current

is about 300 rna.

This

fluctuation will be affected by the nature

of

the

speech content

and

the individual voice. Generally

speaking, the indication will be higher for long

drawn

out

vowel sounds

than

it

is for crisp consonant sounds.

Inclusion

of

an

effective ALC circuit

in

the

NCX-5 has diminished

the

importance

of

the micro-

phone gain control. A

MIC

GAIN

control has been

provided because

of

the wide variety

of

microphones

and

large variation in

output

levels even

of

micro-

phones

of

the same type.

As

the

MIC

GAIN

control

is rotated from the full ccw position,

the

current on

voice peaks will increase to approximately 125 rna.

As

MIC

GAIN

is further increased, little additional

change will

be

noted on

the

meter.

The

MIC

GAIN

control should be set slightly above

the

point where

average current reaches the

125

rna level

on

the

meter. Should

the

control be advanced well above

this point,

the

ALC

can

no longer handle the drive

level,

and

severe distortion may

be

generated.

For

AM

operation with

the

CARRIER

BAL-

ANCE control set as described in paragraphs 3.1.8

and

3.2.5, there will

be

a steady meter reading

of

150 rna.

If

the

MIC

GAIN

control

is

advanced

during speech, AM modulation

of

the final amplifier

will occur.

When

the

MIC

GAIN

control setting

reaches a point where the meter just indicates a

slight flicker

of

speech peaks, modulation

is

100%.

Operation with the

MIC

GAIN

control above this

point should be avoided, since excessive drive will

cause clipping

of

the modulation envelope,

and

this

will result

in

unwanted spurious transmission outside

of

the

passband

of

the

NCX

-5.

3.2.12

THE

'TEN-

METER

SEGMENT

SWITCH

If

it

is

desired to operate

on

one

of

the

10-meter

segments other

than

28.5-29.0, selection

of

the appro-

priate 500

Kc

segment

is

made

by the 10-meter switch

concentric with the PA

TUNE

control.

The

crystal

for

the

segment from 28.5

to

29.0

is

supplied with

the

NCX

-

5.

If

one

of

the

other segments

of

the

band

is desired, the appropriate crystal must be plugged in.

Sockets are

near

the

existing crystal

on

the

sub-chassis

in

the front right-hand corner

of

the NCX-5.

The

corresponding frequencies

and

crystals

are:

28.0-28.5

Me

segment-crystal frequency 24.5

Me;

29.0-29.5

Me

segment-crystal frequency 25.5

Me

;

and

29.5-30.0

Me

segment-crystal frequency is 26 Me. These fre-

quencies are also shown

on

the frequency

chart

under

''Theory

of

Operation." Ten-meter segment crystals

are available from

the

Service Department

of

the.

National Radio Company.

BLOCK

DIAGRAM

FIGURE

2

KEY

,

I

~-

1

...1

DRIV

ER

MIC

1liil._

@------~-

MICROPHONE

PRE-AMPL

2ND

MIXER

1ST

MIXER

I

BUFFER VFO

L - - -

------

- -

---,

I

_

~SPEECH

~AMPL

I

•

I

1sr

11F

10

S·

METER

AMPL

PRODUCT

DETECTOR

LEGEND

·

= RECEIVE PATH

----

TRANSMIT

PATH

--

CONTROL PATH

:==

TRANSMIT

AND

RECEIVE PATH

SECTION

4

THEORY

OF

OPERATION

4.1

GENERAL:

The

NCX-5 transceiver, designed to cover

the

80

through 10 meter

amateur

bands, combines a

double conversion superheterodyne receiver

and

single

sideband transmitter,

both

employing a common

crystal lattice filter.

The

final Pi network, mixer

and

driver tuning·circuits

of

the

transmitter also serve as

RF

circuits for

the

receiver.

The

carrier oscillator

and

VFO

are

common to

the

receiver

and

transmitter

circuits while

the

receiver first

lF

stage is used as a

low level amplifier in

the

transmitter-exciter function.

The

use

of

common filter

and

RF

input

components

results in

an

extremely sensitive

and

image-free, se-

lective receiver

and

in

a high quality, low distortion

SSB transmitter.

The

operation

of

the

NCX-5

is

best understood

by reference to

the

block diagram, figure 2,

and

the

frequency

chart,

figure

3.

4.2

THE TRANSMITTER:

The

transmit signal

path

of

the NCX-5 is indi-

cated

on

the

block diagram

by

a dashed line starting

at

the

mike

jack

and

carrier

oscillator.

The

micro-

phone

input

circuit

is

designed for high-impedance

dynamic

or

crystal microphones

and

provides for a

push-to-talk microphone circuit.

The

microphone is

connected directly

to

the

grid

of

the

pentode section

of

a

6GH8

(V8A)

tube

which operates as a preampli-

fier.

The

signal is

then

fed through

the

microphone

gain control

to

one triode section

of

the

12AT7 (V6A)

speech amplifier.

The

plate circuit

of

this speech

amplifier

is

coupled

to

one

of

the

deflection electrodes

of

the

7360 (V10) balanced modulator.

A 12AU7 (V7)

tube

is

used for

the

two carrier

oscillators.

Each

crystal

is

permanently connected

to

its triode section,

and

sideband switching

is

accom-

plished by applying a negative bias

to

the

section to

be

turned

off.

The

carrier signal appears across a

common resistive plate load

and

is

fed

to

the

grid

of

the

7360 balanced

modulator

tube V-10. A D.C.

network containing

the

carrier balancing control

potentiometer is connected to

the

deflection electrodes

of

the

7360.

In

addition, a

trimmer

provides phase

balance for maximum

carrier

suppression.

The

bal-

anced primary winding

is

coupled to a single-

en

ded

secondary which serves as

the

input

source for

an

eight-pole crystal lattice filter.

11

The

crystal lattice filter

is

resistance terminated

and

coupled directly

to

the

grid

of

the 12BA6 {V15)

first

IF

stage.

The

single-tuned plate circuit

is

coupled

to

the

grid

of

the

12BE6 (V3) first transmit mixer.

The

VFO

uses a 2N706 (

Q1)

NPN

transistor

oscillator

and

a 2N2188

(Q2)

PNP

transistor buffer.

All biasing resistors

and

tank

circuit capacitors are

chosen for low noise

and

temperature characteristics.

Power for

the

VFO

circuits

is

double-regulated by

a zener diode regulator fed from

the

regulated +150

volt bus.

The

result

is

a

VFO

circuit with a total

drift

from

"turn

on"

of

less

than

100 cycles

in

any ·ten-

minute period, including variations of external supply

voltage

and

amb

ient temperature.

The

main tuning

capacitor

is

completely linear with

an

accuracy

of

1

Kc

at

any point within

the

500

Kc

tuning range.

Output

from

the

VFO

is taken from

the

collector of

the

2N2188 (

Q2

)

and

fed

to

the

oscillator grid

of

the

12BE6 (V3) first transmit mixer.

The

output

from

the

first transmit mixer (V3)

is

always in

the

3.5

to

4.0

Me

band.

This

signal is fed

through a bandpass double-tuned circuit

to

the

grid

of

the

pentode section

of

the

6KE8

(V4B) second

transmit mixer.

The

triode section

of

the

6KE8

is

used as a crystal oscillator which feeds

both

the

second

transmit mixer

and

the

first receive mixer.

The

plate circuit

of

the second transmit mixer

is single-tuned

and

feeds the grid

of

the

6GK6

(V5)

driver.

The

single-tuned plate circuit

of

the

driver

feeds

the

grid of the final amplifier.

The

coils

in

the

plate circuits

of

the

transmit mixer

and

driver

are

band

switched for the 80, 40, 20, 15,

and

10 meter

amateur

bands.

The

tuning

gang

is

tracked so

that

exciter

tuning

can

be accomplished with only

one

con-

troL

The

gains

of

the transmit mixer

and

driver

are

such

that

a driving signal in excess

of

100 volts

can

be

obtained

at

the grid

of

the

final amplifier, thus

assuring linear operation

of

the

exciter

to

well above

the level necessary

for

proper drive.

The

final amplifier employs a

pair

of

6GJ5

(V1

and

V2)

tubes operating in parallel. A bias control

on

the

rear

apro

n sets proper idling current.

The

plates

of

the

6GJ5 final amplifier are coupled

to

a

high-efficiency Pi network.

The

band

switch selects

proper

inductance,

tuning

and

load capacitance to

match

a

40

to

60

ohm

resistive load over

the

entire

80, 40, 20, 15,

and

10

meter

amateur

bands.

The

Pi network is designed for continuous operation

at

a power level

of

200 watts input. A small adjustable

capacitor coupled from

the

plate of

the

6GJ5 final

amplifier

to

the

partially by-passed

return

of

the

final

grid circuit coils (driver plate coils) provides neutral-

ization.

When

the final amplifier is properly neutral-

ized, maximum

output

on

a matched

antenna

will

occur

at

the

point

of

plate

current

dip

as indicated

on

the

meter

.

An

effective ALC (automatic level control) cir-

cuit is included.

If

the

final amplifier grids

are

over-

driven

on

voice peaks, the grids will actually see a

driving signal positive with respect

to

the

cathodes,

and

grid

current

will result.

This

current will cause

a negative voltage change

on

the

bias circuit.

The

resulting audio signal

on

the

bias circuit

is

capacitively

coupled

to

a voltage-doubling rectifier.

This

rectifier

will provide a negative

D.C

output

which is coupled

to

the grid

return

of

the

12BA6 (V15) first

IF

am-

plifier.

When

overdrive occurs, the gain

of

the

first

IF

amplifier

is

reduced, resulting

in

less driving signal

at

the

final amplifier. Charging takes place rapidly

.from

the

low-impedance bias source through

the

recti-

fying diodes,

but

the negative ALC voltage cannot

discharge through the reverse biased diodes, resulting

in

a fast

attack-slow

release action. A gating diode

prevents cross connection

of

the ALC

and

AGC

cir-

cuits

at

the

common

IF

grid return point.

The

ALC

circuit will provide automatic level control for input

signal variations

of

more

than

10 db.,

and

makes the

setting

of

the

MIC

GAIN

control quite noncritica

l.

In

addition, sudden changes

in

voice level

or

disturb-

ing background noises

are

all instantly controlled

without overdrive

and

distortion

of

the

NCX-5

trans-

mitter.

4.3 THE

RECEIVER:

The

receiver circuits

are

indicated by

the

double

solid lines

in

the

block diagram.

The

receiver

RF

cir-

cuits

are

common to the transmitter

RF

circuits.

The

high-impedance point

of

the

transmitter Pi network

is capacitively coupled to

the

grid of a 6BZ6

(Vll)

RF

amplifier.

The

tuned

circuits

at

the

plate

of

the

transmit driver

and

plate

of

the transmit mixer are

the

input

and

output

circuits

of

the

12BA&

(V12)

second

RF

amplifier.

They

provide for receiver

RF

selectivity

and

common receiver-transmitter tuning.

The

output

from the second

RF

amplifier

is

coupled

to

the

signal grid

of

the

first receive mixer 12BE6

(V13).

The

oscillator grid is fed from

the

6KE8

(V4A) crystal oscillator.

The

plate

of

this mixer

is

coupled to

the

signal grid

of

the

12BE6

(Vl4)

second

receive mixer.

VFO

signal

is

coupled

to

the·oscillator

grid

of

this mixer.

The

plate

circuit

of

the· second

receive mixer is connected directly across the second-

ary

of

the balanced modulator transformer which

serves as

the

input

coil to

the

crystal lattice filter.

The

output

of

the

crystal lattice filter, as

in

the

transmitter, couples to

the

input

of

a three stage

single-tuned

IF

amplifier operating

at

approximately

6.02

MC.

The

detectors

and

AGC circuits

are

fed

12

through separate voltage dividers.

The

product de-

tector employs one triode of

the

12AX7 tube (V18A)

with the signal from one

IF

voltage divider fed to

the grid. A

BFO

signal

is

coupled from the crystal

controlled 12AU7 (V7) carrier oscillator

to

the

cathode

of

the

product

detector,

and

the

resulting

audio signal is obtained across a resistive load

in

the

plate circuit.

For

AM

operation, a

se

parate

diode de-

tector is connected.

The

output

from

the

detectors is coupled

to

the

audio gain control,

and

then

to

the

grid

of

the

re-

maining triode section

of

the 12AX7 (V18)

tube

functioning as a grid-leak biased, first audio ampli-

fier.

The

plate circuit

is

coupled to

the

grid

of

the

6AQ5 (V19) audio

output

stage.

The

audio

output

stage feeds the

output

transformer having a 3.2

ohm

secondary.

This

output

signal·

is

also available

at

the

phone jack.

The

low-impedance

nature

of

the phone

jack

feed permits use

of

either high-

or

low-impedance

phones.

A secondary feed is

obta

ined from

the

plate cir-

cuit

of

the

last

IF

amplifier

and

is fed

to

a voltage-

doubling AGC rectifier.

The

low-impedance driving

source

pro

vides a

rapid

charge

of

the

AGC bus.

When

the signal disappears,

the

negative AGC bus

cannot

discharge

through

the diodes, which provides

a long release time, thus giving

the

AGC

a very ef-

fective, fast-attack, slow-release action.

The

AGC

is

fed

to

the

grid

of

the remaining

half

of

the 12A

T7

(V6B) S-meter amplifier. AGC is connected

to

the

grid returns

of

the

RF

stage, second

IF

stage,

and

through

the gating diode to

the

first

IF

stage for

control.

4.4

THE

VOX

CIRCUITS:

Before considering the switching operations, we

must first discuss

the

VOX

circuits.

The

signal which trips

the

relay from receive

to

transmit is derived from two sources.

The

first source

is

the

VOX

signal which is picked

up

after

the micro-

phone preamplifier

and

separately amplified

in

a

two stage amplifier consisting

of

V9A

and

V9B

(12AU7).

The

other

signal is derived from the plate

of

the

audio

output

tube

and

is

called the

ANTI-

VOX

signal.

Both signals are rectified,

the

VOX

signal so as

to

make a negative voltage, the

ANTI-VOX

signal

making a positive voltage.

The

two D.C. voltages

are applied in series

to

the

grid

of

the

relay control

tube.

The

circuit constants in

the

VOX

and

ANTI-

VOX

detectors

are

arranged

so

that

the

D.C. voltage

derived from the

ANTI-VOX

detector

is

always

larger

than

the

voltage generated

in

the

VOX

channel

from loudspeaker information.

Additional information entering

the

microphone

is amplified through

the

VOX

amplifier

and

will de-

velop enough negative voltage

at

th

e grid

of

the relay

tube

to

let

the

relay fall off

and

place the circuit

into transmit position.

The

VOX

and

ANTI-VOX

detector time con-

stants are so arranged

that

the

circuits will drive

the

relay tube grid negative in a very short time.

At

the

end

of transmision,

the

relay control signal

cannot

discharge backwards through

the

diodes.

The

dis-

charge time

is

controlled by R7,

the

DELAY

control

which

can

be set from a fraction of a second

to

sev-

eral seconds.

This

circuit

is

also used in

the

CW

position

and

will be discussed

later

·.

4.5

THE

FUNCTION

SWITCHES:

The

following paragraphs describe

the

operation

of

the

various switching circuits with

the

FUNC-

TION

switch

in

all possible positions.

4.5.1

FUNCTION

SWITCH

OFF

In

this position

the

FUNCTION

switch inter·

rupts the primary power, either directly in case of

the

NCX-A

power supply

or

through a remote relay

in

the

NCX-D

12

volt D.C. supply.

The

position

of all

other

switches becomes irrelevant.

4.5.2

FUNCTION

SWITCH

SSB

In

this

position

the

following circuits

are

set

up:

The

VOX

-PTT

switch,

the

product detector,

and

the

microphone amplifier

are

connected

into

the

cir-

cuitry.

The

key jack is disconnected to prevent acci-

dental keying.

Now

three

different types of operation are

possible:

4.5.2.1

VOX

OPERATION

VOX

switch

in

VOX

position

and

the

MOX-

OFF

switch

in

OFF

position.

In

this combination

the

VOX

and

MOX

switches

ground

the

keying diode.

Voice information from the microphone will override

the

ANTI-

VOX,

as described before, tripping the

relay.

The

relay will transfer

B+

to

the

final

and

other

transmitting tubes. Negative bias

is

removed

from various transmitting tubes

and

applied to re-

ceiving tubes

and

the

first

audio

amplifier for quiet

switch over.

At

the

end

of

transmission

and

after

the preset DELAY,

the

relay will pull

in

again,

placing the set

in

receiving condition.

4.5.2.2

PUSH-TO-TALK

OPERATION

VOX-PTT

switch on

PTT,

MOX-OFF

switch

on

OFF

position.

The

output

of

the

VOX

amplifier

is

now shorted

to

ground,

and

the

push-to-talk contact

is

connected across

the

transmit bias line.

When

the

push-to-talk contact

is

pushed,

the

bias line (135) is

grounded, which removes

the

disabling bias from

transmitting tubes.

The

bias

is

also removed from

the

13

first transmit mixer.

The

screen of this ·miXer tube

V3 (12BE6) will now

draw

current, causing a re-

duction of screen voltage. A voltage divider connected

from this screen to

the

-80

bias line will develop a

negative signal which

is

tied through

the

VOX-PTT

and

the

MOX

switch

to

the keying

and

PTT

diode.

The

keying

and

PTT

diode feeds

the

grid of

the

relay

tube.

The

relay tube will be biased off,

the

relay falls

out,

and

the

set

is

in transmitting position.

The

negative signal developed

at

the

first trans-

mit mixer screen

is

also fed to

the

product detector

and

audio

output

amplifier for quiet switching.

On

release of

the

push-to-talk button,

the

nega-

tive bias reappears

on

the

transmit tubes.

The

grid of

the relay control

tube

returns

to

normal,

the

relay

pulls in,

and

receiving conditions

are

restored.

4.5.2.3

MOX

OPERATION

With

the

MOX

switch in

the

MOX

position,

the transmitter bias line (135)

is

grounded directly.

Switching occurs as with

PUSH-TO-TALK

opera-

tion. Returning

the

MOX

switch to

OFF

will

turn

the transmitter off

and

put

the

set

into

receive con-

dition.

4.5.3

FUNCTION

SWITCH

IN

AM

POSITION

The

AM

position of

the

FUNCTION

switch

transfers the

input

of

the

audio

amplifier to

the

out-

put

of

the

AM

detector. Also, disabling bias is applied

to

the

carrier oscillator in use during receiving con-

ditions

to

silence

the

BFO

signal.

VOX,

PTT,

MOX

operation functions now op-

erate

in

the

same

manner

as described

under

SSB

(4.5.2).

4.5.4

FUNCTION

SWITCH

IN

CW

POSITION

In

this pos

it

ion

the

FUNCTION

switch will

disconnect

the

VOX-PTT

switch, ground

the

plate

of

the

microphone preamplifier

to

prevent any speech·

information from coming through, connect

the

input

of

the

audio

amplifier

to

the

output

of

the

product

detector,

and

connect the

KEY

jack

to

the

trans-

mitter

bias line.

When

the

key

is

depres

se

d

the

first time, the

transmitter bias line (135)

is

grounded, placing

the

transmitter tubes

and

the first transmit mixer into

operation. As described above

under

SSB operation,

PUSH-TO-TALK

(paragrap

h 4.5.2.2), the screen

divider of

the

first transmit mixer will now actuate

the relay tube through the keying diode.

The

relay

will fall out, placing

the

NCX-5 into

the

transmitting

position.

From

here

on

in,

further

keying

is

done by

grid-block method, since

the

DELAY

on

the

relay

control tube will hold

the

transmit relay

in

for a

predetermined time. Effective break-in keying

is

therefore realized.

The

VOX-PTT

circuits are dis-

abled so

that

the

microphone

can

be left

in

its jack.

The

MOX

switch, however, will still

actuate

the

transmitter.

4.5.5

FUNCTION

SWITCH

IN

'rUNE

POSITION

In

this position

the

FUNCTION

switch will

ground

the

transmitter bias line, placing

the

trans-

mitter

into

operation, as described

under

"SSB-

PTT

Operation"

(paragraph

4.5.2.2)

and

ground

one

of

the

balanced modulator deflection plates, providing

a strong signal

through

the

system.

'rhe

MOX,

VOX,

PTT

,

and

key circuits

are

disabled

and

have

no

in-

fluence

on

the

tuning

procedure.

4.6

RELAY

F

UNC

TI

ON

S:

In

the

foregoing discussion,

the

exact

nature

of

the

relay switching was

not

described.

The

six-pole

double-throw relay

is

actuated

by the

plate

current

of

the

6GH8

re

lay

tube

V8B.

The

NCX-5

is

placed

in

a transmit

cond

ition when

the

relay

is

de-energized.

The

first set

of

contacts, 5, 6,

and

7, transfers

+220 volts between transmit

and

receiving functions.

Final

Output

Transmit

Driver

Second

Transmit

Mixer

3.5-4

7-7.5

Receiver

RF

Amplifier

Receiver

Mixer

Input

Crystal Osc. None

11

First

Transmit

Mixer

Output

3.5-4

4--3.5

First Receive

Mixer

Output

USB 9.5236 10.02

10.0236 9.52

VFO

LSB 9.52 10.0236

10.02 9.5236

Carrier

Osc. USB 6.0236 6.02

Second Receive

Mixer

Output

Receiver

IF

LSB 6.02 6.0236

Contacts 8, 9,

and

10 transfer

the

bias

on

the

varactor

diode

in

the

VFO.

This

varactor

is

actuated

by a bias depending

on

the

setting

and

switching

of

the

TRANSCEIVE

VERNIER

control

during

re-

ceiving periods

and

by a

fi

xed bias

during

trans-

mitting

periods.

Contacts

11

and

12 are closed

during

transmit

and

are

brought

out

on

the

rear

apron

of

the

NCX-5

for operation

of

the

NCL-2000 linear amplifier.

Contac

ts 14, 15,

and

16 operate as follows:

The

relay

arm,

contact 15, grounds t

he

AGC

line

of

the

receiver

at

contact 14

to

prevent excessive

AGC

build-up during transmit periods

and

to

assure a

pro

mpt

recovery

of

the

receiver

when

req

uire

d.

Con-

tact

15 grounds

the

screens

of

the

final amplifier

at

contact 16,

during

receiving periods.

Contac

ts 17, 18,

and

19 also

are

grounding con-

tacts:

the

arm, contact 18 connects

the

meter

at

con-

tact

17

to

read

the

final cathode

current

during

transmit periods; contact 19,

grounded

during

re-

ceiving periods,

is

connected

to

the

accessory socket

for operation

of

the

external VX-501 console.

Contacts 20, 21,

and

22

gro

und

the

bias line

either

for receive

or

transmit,

plac

ing

the

appropriate

tubes

into

operation as desired.

14-14.5

21-21.5 28-28.5 28.5-29

29-29.5

29.5-30

18 25 24.5

25

25.5 26

4--3.5 4--3.5

3.5-4

3.

5-4

10.02 10.02 9.5236 9.5236 9.5236 9.5236

9.52 9.52 10.0236 10.0236 10.0236

10

.0236

10.0236 10.0236 9.52 9.52 9.52 9.52

9.5236 9.5236 10.02 10.02 10.02 10.02

6.02 6.02 6.0236 6.0236 6.0236 6.0236

6.0236 6.0236 6.02 6.02 6.02 6.02

FREQUENCY

CHART

FIGURE 3

14

SECTION 5

NCX-5 TEST AND ALIGNMENT

NOTE:

TEST

AND

ALIGNMENT

OF

THE

NCX-5

SHOULD

ONLY

BE

PERFORMED

BY

COM-

PETENT,

QUALIFIED

PERSONNEL.

5.1 EQUIPMENT REQUIRED:

1.

Signal generator providing

output

at

the

following frequencies: 6.0218

Me,

3.5 Me,

4 Me, 7 Me, 7.3 Me, 14.0 Me, 14.4 Me, 21.0

Me, 21.5 Me, 28.0 Me, 28.5 Me, 29 Me, 29.5

Me.

2.

Vacuum

tube voltmeter

(VTVM).

3.

Standard

output

meter.

4. Sweep generator capable of sweeping

at

ap-

proximately 60 cycles

per

second over a fre-

quency range from approximately 3

to

4.5

Me.

5. High-frequency oscilloscope covering the

range from

DC

to 30

Me

with a

maximum

sensitivity of 50 mv

per

centimeter

or

better

and

a low capacity

input

probe (Tektronix

type 545 with type L preamplifier

or

equiva-

lent).

6. External receiver capable of receiving

at

9.

72

Me.

7.

50

ohm

dummy

load with calibrated

output

meter covering

the

frequency

range

from 3.5

to

30 Me. (A high frequency vacuum tube

voltmeter with a 100 volt full scale range

may

be substituted for the calibrated

output

power

meter.)

8. Power supply capable

of

supplying + 700

volts

at

300 rna,

+280

volts

at

200 rna

and

-80 volts

at

6 rna.

9. 1000 cycle

audio

generator with

an

output

level of 10 mv.

10.

High

quality microphone equipped

with

push-to-talk button.

11.

Transmitting

key.

12. Suitable alignment tools for adjustment of

coils

and

capacitors.

13.

XCU-27

crystal calibrator.

15

5.2

INITIAL CONTROL SETTINGS:

FRONT

PANEL

RF

and

AF

GAIN

..

.

...........

.

FUNCTION

Switch

..........

. .

PA

TUNE

..........

.

.........

.

PA

LOAD

and

EXCITER

TUNE

BANDSWITCH

..

...

..

........

.

TRANSCEIVE

VERNIER

.....

.

SIDEBAND

Switch

......

.

.....

.

10-METER

Switch

........

..

...

.

MOX-OFF

Switch .

..

.......

.

..

.

VOX-PTT

Switch . . .

...

.......

.

REAR

PANEL

BIAS

INSIDE TOP

COVER

MIC

GAIN

.

....

..............

.

CARRIER

BALANCE

......

.

..

.

VOX

GAIN

.

.............

.

...

.

VOX

DELAY

.

................

.

Power Connections:

Full cw

OFF

Full cw

Full ccw

3.5

Me

OFF

USB

28.5

Me

OFF

PTT

Mid-range

Full ccw

Full cw

or

ccw

Full ccw

Connect

the

power supply

with

the 700 volt out-

put

turned

off.

The

heater

wire connecting the two

6GJ5

sockets should be removed.

5.3

IF ALIGNMENT

PROCEDURE:

Turn

the

FUNCTION

switch to SSE.

In

a few

seconds

the

relay should close, indicating

that

the

NCX-5

is

in a receive condition.

Connect

the

audio

output

meter

to the speaker

leads.

This

may be conveniently done by plugging

the

audio

output

meter into

the

phone

jack. Connect

the

signal generator

through

a 1000

pF

capacitor

to

th

e

grid (Pin 7) of the 12BE6 (V-14) second receive

mixer. Set the signal generator for

output

at

6.0218

Me. A 1

to

2Kc

beat note should be

heard

. Align

the

slugs of

the

first, second,

and

third

IF

transformers

(T-4,

T-5,

and

T-6

),

as well as the bottom slug of

the

balanced modulator transformer

(T-1)

for maxi-

mum

output,

being careful to avoid overload of the

receiving channel.

The

signal generator

output

should

be reduced throughout this alignment procedure so

that

an

output

of

100

mw

is

never exceeded.

5.4

BALANCED

MODULATOR

ADJUSTMENT:

Connect

the high-frequency oscilloscope

to

the

grid

(Pin

1) of

the

first

IF

amplifier 12BA6

(V-15).

Place

the

MOX

-

OFF

switch in

MOX

position.

The

relay in

the

NCX-5

should open, placing

the

unit

in

a transmit condition. Adjust

the

top

and

bottom

slug

of

the

balanced modulator transformer

(T-1)

for

maximum

indication

on

the

scope. Carefully

adjust

CARRIER

BALANCE control for

minimum

indica-

tion

on

·

the

scope.

This

should occur

near

mid-range

of

the

control.

Return

the

CARRIER

BALANCE

control

to

full cw

or

ccw.

If

there

is

no

indication

at

this point,

the

carrier oscilloscope trimmer (C-6) cor-

responding

to

the

upper

sideband crystal

at

6.0234

Me

may

be

adjusted

to

insure

that

the

carrier oscilla

tor

is functioning.

5.5

CARRIER

OSCILLATOR

SETTING:

With

connections set as for balanced

modulator

adjustment,

adjust

(C-6) corresponding

to

the

6.0234

Me

crystal

until

the signal level

is

0.2 volts peak-to-

peak as indicated on

the

oscilloscope.

Set

the

SIDEBAND

switch

to

LSB. Adjust (C-5)

corresponding

to

the

6.020

Me

crystal until

the

signal

level is 0.2 volts peak-to-peak as indicated

on

the

oscilloscope.

Return

the

SIDEBAND

switch

to

USB

and

re-

move

the

oscilloscope connection.

Return

MOX-OFF

switch

to

OFF.

5.6

TRANSMITTER

BANDPASS

TUNING:

Connect

the

sweep

generator

to

the

signal grid

(Pin 7) of

the

first transmit

mixer

12BE6

(V

-3).

Con-

nect

the

oscilloscope

to

the

junction

of

C-134, R-76,

and

the

cable feeding

the

grid

of

the

second transmit

mixer. Press

the

MOX-OFF

switch

to

MOX.

The

CARRIER

BALANCE control may be adjusted for

minimum

carrier

to

avoid

unwanted

oscilloscope in-

dications.

Adjust

the

top

and

bottom slugs

of

the

transmit bandpass coil

(T-2

) for

maximum

display

amplitude

and

proper response.

The

3.5

and

4.0

Me

outputs of

the

signal generator

may

be used as

marker

frequencies.

When

properly aligned,

the

oscilloscope

display should be as indicated.

3.5Mc

MARKER-

3

TO

6db

FROM

PEAK

4.0Mc

-MARKER

3

TO

6db

FROM PEAK

Return

MOX-OFF

switch

to

OFF

and

discon-

nect oscilloscope

and

sweep generator leads.

16

5.7·

RECEIVER

BANDPASS

TUNING:

Connect

the

sweep generator

to

the

signal

grid

(Pin 7) of the first receive mixer 12BE6

(V

-13) .

Con-

nect

the

oscilloscope

to

the

signal grid

(Pin

7) of

the

second receive mixer 12BE6

(V

-14) .

Ad

just

the

top

and

bottom slugs of

the

receiver bandpass coil

(T-3)

for

maximu

m display

amplitude

and

proper response

similar

to

that

obtained for

the

transmit bandpass coil.

Disconnect

the

oscilloscope

and

sweep generator con-

nections.

5.8

VFO

FREQUENCY

ALIGNMENT:

Connect

the

high frequency signal generator

to

the

signal grid (

7) of the first transmit mixer

12BE6 (

V-13).

Preset

the

sideband switching trim-

mer

(C-16)

and

the

temperature compensating trim-

mer

(C-18)

to

mid-range. Set

the

signal generator

frequency

to

4 Me. Adjust the

VFO

coil (L-27) for

zero beat. Set

the

generator

input

to

3.5

Me

and

tune

the

main

tun

ing dial

toward

3.5 Me. A

beat

note

should be obtained

in

the

regi

on

of 3.5

Me

on

the

dial.

If

this

beat

note occurs

at

a dial setting above 3.5

Me,

the

VFO

trimmer

(C-1

7")

sliould be

turned

to

reduce

the

capacity.

If

the

beat

note occurs below 3.5

Me

on

the

dial, increase

the

trimmer

capacity.

Return

the signal generator

and

main

tuning

dial

to

4 Me.

Reset

the

VFO

coil slug for zero

beat

and

again ob-

serve

the

location

of

the

beat

note

near

3.5

Me

with

the

signal ge

nerator

set

to

3.5 Me.

This

procedure

should be repea

ted

until

the 3.5

Me

beat

note

and

the

4.0

Me

be

at

note occur within 500 cycles

of

the

dial markings.

5.9

VFO

LINEARITY

ADJUSTMENT:

A special linearity

ad

ju

stment (consisting

of

two

segmented plates

and

a stator) is incorporated

in

the

rear

section

of

the

NCX-5

VFO

capacitor. After

ad-

justmen

t of

the

VFO

frequency

at

4.0

and

3.5

Me,

it

will

be

necessary

to

set

the

VFO

linearity.

Insert

the

crystal calibrator

into

the

crystal cali-

brator

socket.

With

the

crystal calibrator

turned

on

and

set for 100

Kc

markers,

it

should be possible

to

obtain

a zero

beat

at

the

3.5

and

4.0

Me

points which

have previously been set.

The

main

tuning

should now

be adjusted

to

3.9, 3.8, 3.7,

and

3.6

Me.

At

each

of

these points zero

beat

should occur within

+500

cycles

of

the

exact dial frequency.

If

necessary, one

(or

both)

of

the segmented adjusting plates should be

bent

as required

to

achieve

proper

calibration.

If

the

indicated frequency

is

too low

at

the

zero

beat

point,

one

or

both

of

the

plates should be moved toward

the

stator.

If

the indicated dial reading

at

zero

beat

is too

high,

the

plate should be moved away from the stator.

It

is

important

that

this linearity correction be

made

on

a

gradual

basis.

The

entire correction

at

any one

point should

not

be

made

with

a single segment

of

the

correction plate.

When

properly aligned,

the

corrector

segments will lie

in

a smooth curve.

5.10

VFO

SIDEBAND SWITCHING

ADJUSTMENT:

Set

the

main

tuning

to

zero beat

at

3.8

Me,

ro-

tate the sideband selector switch to LSB.

The

fre-

quency obtained should still

be

zero beat.

If

it

is

not,

set

the

sideband trimmer (C-16) for zero beat.

As

the

sideband selector switch

is

rotated

from LSB

to

USB,

there should be no change

of

frequency.

There

is

a

small interaction of this adjustment with

the

VFO

alignment.

The

VFO

alignment should be readjusted

if any

error

is introduced.

5.11 TEMPERATURE COMPENSATING

ADJUSTMENT:

During

alignment

of

the

NCX-5, its

VFO

should

be checked.

If

drift

is excessive,

the

temperature com-

pensating capacitor should be adjusted

to

provide

greater

or

less compensation.

Drift

towards a lower

dial reading

on

80

meters indicates excessive tempera-

ture

compensation

and

the

compensating trimmer

(C-18) should be

turned

to

reduce capacity. A drift

toward a higher dial reading indicates insufficient

compensation

and

the

trimmer

should be

turned

for

greater capacity. Adjustment

of

the compensating

trimmer will change

the

VFO

frequency. Complete

realignment

of

the

VFO

can

be

avoided by

the

follow-

ing procedures: Set

the

NCX-5

to

zero

beat

at

the 3.8

Me

dial setting. Adjust

the

compensating

trimmer

as

required

and

immediately adjust the

VFO

trimmer

(C-17) to

return

the

NCX-5

to zero beat.

If

this pro-

cedure is carefully followed,

the

dial calibration should

not

be

seriously affected.

If

a

major

correction has

been made, the dial calibration should be checked

and

the alignment

of

the preceding sections should be re-

peated

if

necessary. Disconnect the signal generator

leads from the NCX-5.

5.12

TRANSMIT MIXER AND DRIVER

ALIGNMENT:

Connect

the

high-frequency oscilloscope

to

the

junction

of

C-46, R-42,

and

the grids

of

the 6GJ5

final amplifier. Set the BAND switch

to

3.5

Me

and

the

FUNCTION

switch

to

TUNE.

The

relay should

again

drop

out,

indicating

that

the

unit

has

been

placed in a transmit condition. Set

the

main

tuning

dial

to

3.

.750

Me

and

the

EXCITER

control

to

5. Ad-

just

the

80

meter

mixer coil (L-1

0)

and

the

80

meter

driver coil (L-5) slugs for

maximum

indication

on

the

oscilloscope.

When

the slugs

are

properly adjusted, the

peak-to-peak

output

voltage

on

the oscilloscope should

exceed 130 volts.

Set

the

BAND switch

to

7.0

Me

and

the

EX-

CITER

TUNE

control

to

6. Repeat

the

above pro-

cedure

at

7.300

Me

while adjusting the

40

meter

mixer coil (L-9)

and

the

40

meter

driver coil (L-4).

An

output

of

more

than

130 volts peak-to-peak must

be

indicated

on

the oscilloscope.

17

At

this point a ripple will

appear

on

the oscillo-

scope pattern. Adjust

the

harmonic

trap

(L-29)

to

minimize this ripple.

After

this adjustment is made,

there will be some interaction with

the

tuning

of

the

40

meter

mixer coil (L-9) which must

be

readjusted

for maximum amplitude. Repeat these adjustments

until minimum ripple

and

maximum amplitude

are

obtained simultaneously.

The

setting

of

the harmonic

trap

may

be checked by removing the

11

Me

crystal

in

the

high-frequency oscillator circuit. When the

crystal

is

removed, there should

be

a large

drop

in

the

amplitude

of

the

oscilloscope display.

If

there is

no

such

drop,

the

harmonic

trap

has been mistune4

and

the slug should be withdrawn from

the

coil

and

the

above alignment procedure repeated

on

the proper

trap

frequency.

Set

the BAND switch to 14.0

Me

and

the

EX-

CITER

TUNE

control

to

3.

Repeat

the

above proce-

dure

at

14.250

Me

while adjusting

the

20 meter mixer

coil (L-8)

and

the

20 meter driver coil (L-3) .

Set the BAND switch to 21.0

Me

and

the

EX-

CITER

TUNE

control

to

7.

Repeat

the

above proce-

dure

at

21.250

Me

while adjusting

the

15 meter mixer

coil (L-7)

and

the

15

meter

driver coil

(L-2).

Set the BAND switch to 28.5

Me

and

the

EX-

CITER

TUNE

control to

7.

Repeat

the

above pro-

cedure

at

28.750

Me

while adjusting

the

10 meter

mixer coil (L-6)

and

the

10 meter driver coil

(L-1).

5.13

FINAL AMPLIFIER PRELIMINARY

ADJUSTMENT

(10

METER):

The

NCX-5 construction does

not

provide for

any alignment

of

the final amplifier.

It

is necessary

at

this time to check the final amplifier for proper opera-

tion

at

the

high

and

low ends

of

all bands.

In

addition,

it

is

necessary

to

make a slight final adjustment

on

the

driver plate coils

and

on

the neutralizing capacitor.

These

checks should

be

made in

the

following se-

quence: Connect the heater wire between the 6GJ5

sockets. Place

the

FUNCTION

switch in

the

OW

position

and

allow approximately 30 seconds for

warm-up

of

the

final amplifier tubes.

-CAUTION-

UP

UNTIL

THIS

TIME,

THERE

HAS

BEEN

NO

POWER

APPLIED

TO

THE

FINAL

AMPLI-

FIER.

ALL

CIRCUITS

WHICH

HAVE

BEEN

OP-

ERATING

AND

WHICH

HAVE

BEEN

TESTED

ARE

LOW

LEVEL

CIRCUITS

USING

VOLT-

AGES AND

POWER

NORMALLY

ENCOUN-

TERED

IN

DAY-TO-DAY

RECEIVER

WORK.

FROM

HERE

ON,

VOLTAGES

AND

CURRENTS

MAY

BE

ENCOUNTERED

WHICH

ARE

DANGEROUS

TO

PERSONNEL

AND

TO

THE

TEST

EQUIPMENT

AND

THE

UNIT

UNDER

TEST.

IT

IS

ESSENTIAL

TO

BE

SURE

THAT

NO

PIECE

OF

TEST

EQUIPMENT

BE

MIS-

CONNECTED

INTENTIONALLY

OR

ACCI-

DENTALLY

TO

THE

NCX-5.

IT

IS

FURTHER

IMPORTANT

THAT

PERSONNEL

BE

CAU-

TIONED

AGAINST

CARELESS

HANDLING

WHICH

MAY

RESULT

IN

CONTACT

WITH

DANGEROUS

VOLTAGES.

IT

IS

FURTHER

IMPORT

ANT

THAT

THE

NCX-5

NOT

BE

PLACED

INTO

A .TRANSM

ITTING

CON-

DITION

WITHOUT

PROPER

TUNING,

SINCE

DAMAGE

MAY

RAPIDLY

RESULT

TO

THE

NCX-5.

IN

A

NUMBER

OF

THE

FOLLOWING

TESTS

'rHE

TRANSMITTER

WILL

BE

OP-

ERATED

AT

FULL

POWER

OUTPUT.

IF

MIS-

INDICATIONS

ARE

OBTAINED,

OR

IF

THE

TEST

IS

NO'r

COMPLETED

WITHIN

A

PERIOD

OF

15

SECONDS,

OR

IF

THE

UNIT

IS

NOT

TUNED

UP

WITHIN

A

PERIOD

OF

15

SECONDS,

IT

IS

IMPORTANT

THAT

THE

UNIT

BE

RETURNED

'rO

A

RECEIVING

CON-

DITION.

OTHERWISE,

SERIOUS

AND

PER-

MANENT

DAMAGE

CAN

BE

DONE

TO

THE

FINAL

AMPLIFIER

TUBES

AND

COMPO-

NENTS

IN

THE

FINAL

OUTPU'r

CIRCUIT.

Disconnect all test equipment from

the

NCX-5.

Attach

the

50

ohm

dumm

y load with calibrated out-

put

meter

to

the

NCX-5

antenna

terminals.

With

a

D.C. voltmeter, set

the

bias

at

the

grid

of

the

final

amplifier for maximum negative voltage.

With

the

BAND switch still on the 28.5

Me

band, set

the

main

tuning dial

to

28.75 Me. Now

tum

the

FUNCTION

switch

to

TUNE

and

rapidly peak the

EXCITER

TUNE

for maximum meter reading

on

the combina-

tion S-meter

and

cathode

current

meter. Adjust the

10 meter driver plate coil (L-1) for maximum meter

reading while slowly rocking

the

EXCITER

TUNE

control.

This

will correct for

the

presence

of

the

oscilloscope probe in the previous setting. Now rotate

the

PA

TUNE

control

and

observe whether a

dip

oc-

curs

in

the

plate current reading.

Note

the

power

output

reporded by

the

power

output

meter.

This

power

output

should exceed 100

watts

at

all frequencies providing

the

PA

LOAD

control is adjusted so

that

the

final amplifier draws

300 rna.

With

the PA

TUNE

control set for a plate

current dip,

the

PA

LOAD

control is slowly rotated

in

a clockwise

di

rection.

As

the

PA

LOAD

control

i~

advanced,

it

will be necessary

to

slightly

retune

the

PA

TUNE

control

to

stay

in

the

dip. Continue this

process until

the

minimum reading

in

the

dip

corre-

sponds

to

300 rna on the meter.

5.14

NEUTRALIZING

CAPACITOR:

With

the

FUNCTION

switch in

the

TUNE

position, rotate

the

PA

TUNE

control

to

either side

of

the

resonant point

and

observe the plate current

meter.

It

is necessary

that

the

off resonance

current

exceed 350 rna.

Having

noted

the

off resonance plate

current,

retune

the

PA

TUNE

control

to

the plate

current

dip

at

300 rna

and

observe the power output.

It

should exceed 100 watts. Carefully

rotate

the

PA

18

TUNE

control

to

either

side

of

the

dip

and

observe

whether the power

output

rises

or

falls.

With

a proper

setting

of

the n

eutra

lizing capacitor,

the

power

output

should fall

to

either side

of

the dip.

If

the

power

out-

put

actually rises as the

tuning

control

is

tuned away

from the dip,

it

will

be

necessary

to

adjust the neutral-

izing capacitor.

'rhis

can

be quickly done

on

a trial

and

error

basis by rotating the neutralizing capacitor

and

observing

whether

maximum power

output

oc-

curs

at

the plate

current

dip. As

proper

neutralization

is achieved, maximum power

output

will occur

at

minimum

plate current.

Return

the

FUNCTION

switch

to

CW.

5.15

FINAL

AMPLIFIER PRELIMINARY

ADJUSTMENT .

(80-15

METERS):

Set the BAND switch

to

21

Me

and

the

main

tuning

dial

to

21.250 Me.

Tum

the

FUNCTION

switch

to

TUNE

and

rapidly peak

the

EXCITER

TUNE

for maximum meter reading. Adjust the 15

meter

driver plate coil (L-2) for maximum

meter

reading while slowly rocking

the

EXCITER

TUNE

control.

This

will correct for

the

presence

of

the

oscilloscope probe

in

previous tests. Now rotate

the

PA

TUNE

control

and

observe whether a

dip

ap-

pears

in

the reading. Advance

the

PA

LOAD

in

a

clockwise direction

and

slightly

retune

the

PA

TUNE

control

to

stay

in

dip. Continue this process until

the

minimum meter reading in

the

dip

corresponds

to

300 rna.

The

power

output

should exceed 100 watts

and

proper

neutralization should

be

observed.

Repeat

this procedure

at

the following BAND

switch

and

tu

ning settings, in

each

case adjusting

the

proper driver coil for maximum

meter

indication

while rocking the

EXCITER

TUNE

control.

MAIN

BANDSWITCH

TUNING

DIAL

DRIVER

COIL

14

Me

14.250

Me

L-3

7

Me

7.250

Me

L-4

3.5

Me

3.750

Me

L-5

5.16

FINAL

AMPLIFIER TUNING

CHECKS:

The

proper crystal should be inserted into the

NCX-5 high frequency oscillator for operation

at

BAND switch settings

of

28, 29,

and

29.5 Me.

If

these crystals

are

not

available, final amplifier

tuning

checks in these BAND switch settings

cannot

be made.

Set the BAND switch

to

28.0 Me. Set the

main

tuning

dial

to

28.250 Me.

Tum

the

FUNC'riON

switch

to

TUNE

and

peak the

EXCITER

TUNE

for

maximum meter reading. Rotate

the

PA

TUNE

con-

trol

and

observe

whether

a

dip

appears

in

the reading.

Advance the PA

LOAD

control in a clockwise direc-

tion

and

retune

the

PA

TUNE

control to maintain

the

output

circuit

in

the

dip. Continue this procedure

until

the

minimum reading in

the

dip

corresponds

to

300 rna

on

the

meter. Power

output

at

this setting

should exceed 100 watts

and

proper

neutralization

should

be

observed.

National Radio NCX-5 User manual

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