Hammarlund HX50 Manual

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1

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THE

HX-500

TRAN

MITTE

..

2

DESCRIPTION

-

AND

-

The

Hammarlund

Manufacturing

Co.,

Inc.

460

W

••

t

34th

Street,

New

York

1,

N

Y.

Interna

lonal

Dlvl.lon:

13

East

40th

Street.

New

Vork

16,

•

Y.

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THE

HX-500

TRANSMlTTER

INSTRUCTION

AND

SERVICE

INFORMATION

ESTABLISHED

1910

ISSUE

NO.1

In

order

to

receive

the

full

unconditional

90·day

warranty

against

defective

material

and

workmanship

in

this

receiver,

the

warranty

card

must

be

filled

out

and

mailed

within two

weeks

of

purchase.

Please

refer

to

serial

number of

equipment

in

correspond-

ence,

and refer

to

ins

ide

bock

COver

for

terms

of

warronty.

THE

HAMMARLUND

MANUFACTURING

COMPANY~

INC.

460

West

34th

Street~

New

York

l~

New

York~

U.S.A.

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m

INTRODUCTION

The

HX-500

Exciter-Transmitter

is

a

self

con-

tained

unit

designed

with your

present

and

future

requirements

in

mind.

The

transmitter

is

completely

self

contained;

employing

21

tubes

(plus

four

semi-

conductor

diodes),

and

requires

only

the

addition

of

a

suitable

mike,

key,

or

bug

and

suitable

antenna

system

for

immediate"

on

the

air"

operation.

This

Transmitter-Exciter

covers,

80,

40,

20,

15

and 10

meter

amateur

bands

by

means

of

an

eight

position

rotary

bandswitch.

Four

bandswitch

posi-

tions

are

provided

for

complete

coverage

of

the

10

meter

band

and

the

built-in

VFO

covers

a

range

of

500

KC's.

The

eight

crystals

needed

for

complete

band

coverage

are

supplied.

The

rotating

drum, il-

luminated

slide

rule

dial

is

calibrated

to

indicate

better

than

10

KC's

and

the

tuning

knob

skirt

can

be

read

to

better

th an 200

cycles.

One

rotation

of

the

frequency

knob

covers

two

divisions

or 20 KCS on

the

illuminated

dial

drum.

The

unit

is

capabie

of

transmitting

the

following

types

of

signals:

LSB,

USB, DSB,

CW,

FM, and

FSK.

The

power

output

on SSB

is

70-100

watts;

70-100

watts

on

CW,

FSK,

FM

and 17-25

watts

on DSB (AM).

The

carrier

suppression

on

both

USB and

LSB

is

greater

than -50 db and

the

unwanted

sideband

is

rej

ected

by more

than

-50

db.

Spurious

frequencies

generated

within

the

unit

are

suppressed

to

a

level

of

-50

db or more.

The

intermodulation

distortion

products

have

been

suppressed

beyond

the

-30

db

level.

The

transmitter

output

pi-network

has

been

care-

fully

designed

to match a

52

ohm

transmission

cable

impedance

and

suppress

harmonic

TVI.

A

logarithmic

type

of

carrier

level

indicator

pro-

vides

a very

simple

yet

adequate

means

of

tuning

up and

continuously

monitoring

the

transmitter.

The

VOX

circuit

adjustments

(Sensi

tivity,

Delay

and

Anti-Trip)

are

located

on

the

front

panel.

The

single

sideband

signal

is

generated

III

the

HX-500

Transmitter-Exciter

by

means

of

a

highly

stable

60

KC

oscillator

whose

signal

is

fed

into

a

carefully

balan

ced

diode

modul

ator

and

subse-

quently

applied

to a

series

of

cascaded

overcoupled

and

under

coupled

tuned

circuits

(with

carrier

re-

jection

trap) which

provides

the

necessary

unwanted

sideband

rejection.

The

choice

of

LSB,

USB, or

DSB

transmission

is

determined

by

the

position

of

the

function

switch

which

shifts

the

resonant

fre-

quencies

of

the

60

KC

tuned

circuits

to

provide

the

proper

bandwidth

for

the

desired

mode

of

operation.

All

of the

controls

that

are

required

for

proper

tune

up and

operation

of

the

Transmitter-Exciter

are

provided

on

it's

front

panel

and

these

controls

are

logically

grouped

for maximum

operating

ease.

The

HX-500

was

designed

with you in mind. You

will

find

many

hours

of

pleasure

in

operating

this

truly

fine

communications

instrument.

Page

2

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4 5

flll'l'l.fjlOllfi

t!T~(1iJ

3

2

6

17

18

7

19

20

8 9

10

II

12

Figure

J. The

HX

500

Transmitter

1l0CATION

OF

CONTROLS

I.

R.F.

Output

Level

Meter

II.

Tuning

Dial Drag

or

lock

2.

Calibrate

Level

Control 12.

Frequency

Control

3. Meter

Sensitivity

Control 13.

VOX

Delay

Adjustment

4.

R.F.

Level

Control 14. FSK

-FM

N

Adjustment

5.

Final

Amplifier Tuning Control 15. Anti-Trip

Sensitivity

Adjustment

6.

Function

Switch

Selector

(Type

of

Transmission)

16.

VOX

Sensitivity

Adjustment

7.

Operations

Switch

Selector

17. Key

Jack

(CW

-FSK

40

cycle

Identification)

8. Audio

Level

Control 18. Monitor

Jack

9. Driver

Tuning

Control 19.

Patch

Jack

10. Band

Selector

20.

Microphone

Connector

Page

3

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..

-----------

-----

------~_

..

m

_---_.-

INSTALLATION

UNPACKING

After

unpa~king

the

transmitter

carefully,

make

sure

that

all

tubes,

associated

tube

shields,

and

pilot

lamps

are

properly

seated

in

their

respective

!!lockets.

Inspect

the

unit

for

any

signs

of

damage

during

shipment

and

carefully

read

all

tags

and

labels

for

any

special

instructions

before

discarding

them.

MONI'TOR

JACK

The

microphone

and

key

connections

to

the

trans-

mitter

are

located

along

the

bottom

edge

of

the

trans-

mitter

panel.

A

standard

microphone

connector

such

as

the

Amphenol

type

75-MCIF

or

equivalent

is

required

to

connect

the

microphone

to

the

transmitter.

Any

high

impedance

microphone,

either

crystal

or

dynamic,

will

give

satisfactory

results

when

used

with

this

transmitter.

The

key

or

"bug"

is

con-

nected

to

the

front

panel

receptacle

by

means

of

a

standard

two

contact

phone

plug.

The

key

or

"bug"

may

be

connected

to

the

remote

control

plug,

lo-

cated

at

the

rear

of

the

chassis,

instead

of

the

front

panel

if

desired.

See

Fig.

2 for

remote

key

connec-

tions

on

the

14

prong

plug

located

at

the

rear

apron

of

chassis.

MICROPHONE

&

KEY

CONNECTIONS

The

monitor

jack

provides

a

means

of

listening

to

the

received

signals.

Any

headset

fitted

with

a

standard

two

conductor

phone

plug

can

be

used.

When

the

phones

are

plugged

into

the

receptacle,

the

communications

receiver

speaker

will

be

disabled,

provided

that

the

receiver

output

and

speaker

are

wired

as

shown

in

Fig.

2.

PHONE

PATCH

The

phone

patch

jack

requires

a

standard

two

conductor

phone

plug.

This

input

receptacle

is

con-

nected

directly

across

the

high

impedance

audio

level

control.

Any of

the

phone

patches

available

should

be

useable

when

the

output

is

fed

into

this

jack

(on

the

assumption

that

sufficient

gain

has

been

provided

in

the

patch).

Page

4

117

VOLT

POWER

CONNECTION

Before

inserting

the

line

cord

plug

into

the

power

outlet,

make

certain

that

the

power

source

is

of

the

proper

voltage

and

frequency.

The

Model HX-500

Transmitter-Exciter

is

designed

to

operate

on

105-125

volts,

50-60

cycles

A.C.

Do

not

under

any

circumstances,

connect

this

unit

to

a

source

of

direct

current

as

doing

so

will

blow

the

fuse.

ANTENINA

CONNECTION

The

output

impedance

of

the

HX-500

is

'50

Ohms.

A

suitable

RF

cable

and

cable

connector

is

RG-8/u

coaxial

cable

with

an

Amphenol

type

83-1SP

or

equivalent

coaxial

cable

connector.

The

selection

of

the

type

of

antenna

and

coupler

will

depend

upon

the

band

of

operation

and

the

ob-

jectives

of

the

user.

The

ARRL

publications

are

an

excellent

source

for

information

on

the

design

and

construction

of

various

types

of

antenna

systems.

ANTENNA

RELAY

The

HX-500

is

equipped

with

an

internal

antenna

changeover

relay.

The

typical

Send-Receive

connec-

tions

are

illustrated

in

Fig.

2.A

stanaard

phonograph

plug

is

required

for

the

receiver

connections

to

the

changeover

relay

contacts.

RECEIVER

AUDIO

CONNECTIONS

In

order

to

have

the

VOX

relay

control

the

signals

from

the

station

receiver's

loud

speaker,

the

HX-500

Transmitter

must

be

connected

to

the

station

receiver

as

shown

in

Fig.

2.

In

many

cases

the

blocking

bias

connections

will

be

needed

to

put

the

receiver

in

standby

in

place

of

the

"make

and

break"

contacts

as

shown

in

the

Figure.

BLOCKIING

BIAS

CONINECTIIONIS

A

high

impedance

bias

source

(-lOOV.)

is

provided

to

silence

the

station

receiver

during

periods

of

transmission.

Pin

6 of

the

rear

receptacle

supplies

this

voltage

when

the

VOX

relay

is

energized,

(transmit

position)

and

grounded

in

the

normally

open

position.

Pin

7

is

a

suitable

groun?

connection

for

running

a

shielded

lead

to

the

receiver

if

it

be-

comes

necessary

to

minimize

RF

pick

up

in

the

lead.

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HX-500

TRANSMITTER HQ-170 RECEIVER

--------------_

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(WITH

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WIRING

CONNECTIONS

FUNCTION

GROUND

NORMALLY

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CONTACT}

CENTER

CONTACT

R:~:Y

NORMALLY

CLOSED

CONTACT

-100

V.

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FOR

RECEIVER

BLOCKING

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CW

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40

CYCLE FS K KEY

RECEIVER OUTPUT TRANSFORMER SECONDARY

STATION

RECEIVER

SPEAKER

FSK

RELAY

CONNECTION

FSK

RELAY

CONNECTION

CATHODE

CURRENT

OF

VI5

S.

VI6

(6146'S)

Figure

2.

Typical

Amateur

Station

Wiring

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m

FUNCTION

OF

OPERATING

CONTROLS

FUNCTION

SWITCH

The

Function

Switch

determines

the

type

of

emitted

signal

selected

by

the

station

operator.

The

HX-500

is

capable

of

transmitting

the

following

types

of

signals

as

indicated

on

the

knob:

LSB,

USB,

DSB (AM),

CW,

FSK,

and

FM.

OPERATION

SWITCH

The

five

position

Operations

Switch

turns

the

AC

power

ON

(Standby)

and

OFF,

and

inel

udes

the

MOX,

VOX,

and

Calibrate

positions.

When

manual

control

of

the

transmitter

is

desired,

the

MOX

position

is

used.

In

the

MOX

position,

the

antenna

and

VOX

relays

are

always

energized

and

are

completely

independent

of

control

by

the

VOX

circuit

knobs

(VOX

sensitivity,

VOX

delay

and

anti-trip).

In

the

VOX

position,

the

transmitted

output

is

controlled

by

the

voice

energy

from

the

microphone.

In

this

position,

the

antenna

and

VOX

Relays

are

controlled

by

the

adjustment

of

the

VOX

circuit

controls.

The

proper

setting

of

the

VOX

knobs

is

outlined

in

the

Tuning

Procedure.

In

the

calibrate

position,

the

Antenna

and

VOX

Relays

are

always

in

the

de-energized

position

(receive).

This

position

is

used

to monitor

the

trans-

mitted

signal

in

the

communications

receiver

and

is

also

used

for

zero

beating

the

HX-500

signal

fre-

quency

to

an

incoming

signal

or

desired

frequency.

CALI

BRATE

LEVEL

A

calibrate

level

control

is

included

in

the

trans-

mitter

to

adjust

the

amount

of

signal

fed

into

the

receiver

from

the

transmitter

in

the

Cal

position.

The

Calibrate

Level

knob

is

adjusted

so

that

the

desired

level

of

the

transmitter

output

as

observed

on

"s"

meter

of

Receiver

or

the

loudspeaker,

(or

headset

connected

to

Monitor

Jack)

is

sufficient

for

monitoring.

A

very

limited

amount

of

RF

power

is

"leaked"

from

the

final

amplifier

tank

circuit

to

the

receiver

input

via

the

Antenna

Relay

wiring.

R.F.

LEVEL

The

RF

Level

control

adjusts

the

gain

of

the

5.55

to

6.05

Mcs

broadband

amplifier.

Optimum

RF

output

on

all

bands

is

achieved

with

the

adjustment

of

this

control.

This

is

usually

set

at

4

to

5.

Page

6

AUDIO

LEVEL

The

audio

level

control

adjusts

the

amount

of

audio

gain

required

to

fully

voice

modulate

the

transmitter.

This

is

usually

set

at

5.

DRIVER TUNE

The

Driver

Tune

knob

adjusts

both

the

3rd

mixer

plate

and

driver

plate

tuned

circuits

to

resonance

at

the

frequency

desired.

FINAL

TUNE ,

The

Final

Tune

knob

adjusts

the

output

tank

capacitor

for maximum

RF

output.

The

knob

skirt

is

marked

to

indicate

the

designated

area

on

each

band

w

here

maximum

output

can

be

obtained

as

observed

on

RF

Level

indicator.

BAND

SELECTOR

The

eight

position

Band

Selector

control

selects

the

proper

combination

of

tuned

circuits

and

the

proper

heterodyne

crystal

on

each

band.

The

Band

Selector

shaft

also

indexes

the

direct

reading

dial

drum

which

indicates

the

band

in

use.

METER

SENSITIVITY

The

meter

sensitivity

knob

controls

the

amount of

deflection

of

the

output

level

meter.

Clockwise

rotation

increases

the

sensitivity

of

the

meter

circuit.

The

Output

Level

Meter

is

used

to

tune

up

the

transmitter

to

any

frequency

within

its

range.

The

meter

indication

is

logarithmically

proportional

to

the

RF

voltage

across

the

50

Ohm

output.

This

fea-

ture

gives

the

meter

wider

dynamic

range

of

indi-

cation.

DIAL

DRAG

& LOCK

The

small

knob

adjacent

to

the

Frequency

tuning

knob

has

been

included

in

the

HX-500 for

the

pur-

pose

locking

the

dial

drive

to

a

selected

frequency

and

adjusting

the

tuning

knob

calibration.

Clockwise

rotation

of

this

knob

restrains

the

frequency

knob

from

turning.

It

also

enables

the

adjustment

of

dial

action

or

torque

required

for

personal

preference

of

the

operator.

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IIi

TUNING

GENERAL

The

HX-500

Transmitter

has

been

designed

to

give

the

utmost

in

quick

and

easy

operation

for

the

radio

amateur

operator.

All

operating

controls

are

clearly

identified.

The

slide-rule

type

of

dial

is

marked

off

to

indi-

cate

every

10

kilocycle

change

in

frequency

on

each

of

the

eight

direct

reading

bands.

In

addition

to

the

10

kcs

markings,

every

band

contains

two

heavy

dot

markings

and

two

heavy

diamond

shaped

markings.

The

dot

markings

indicate

the

outer

limits

of

each

amateur

band

in

which

authorized

amateur

communi-

cation

is

permitted.

The

diamond

shaped

markings

have

been

included

to

show

at

a

glance

the

outer

limits

of

each

amateur

phone

band.

Since

the

10

meter

band

extends

over

foUF

band

change

positions,

the

markings

are

included

only

on

the

first

and

last

of

the

four

segments.

The

frequency

tuning

knob

and

dial

lock

knob

are

connected

to

the

variable

capacitor

located

on

the

VFO

sub-chassis

by

means

of

a

spring

loaded

gear

drive

mechanism.

Twenty

five

revolutions

of

the

tuning

knob

covers

a

SOO

Kcs

band

segment.

The

major

markings

on

the

frequency

tuning

knob

are

calibrated

to

indicate

1

Kcs

changes

in

frequency

and

are

sub-divided

to

indicate

frequency

changes

of

two

hundred

cycles

between

each

small

division.

To

accurately

set

the

transmitter

to

a

specific

frequency;

for

example

3962.4

Kcs.,

turn

the

tuning

knob

until

the

dial

pointer

indicates

the

nearest

10

Kcs

point

below

the

desired

frequency

e.g.,

3960

Kcs

and

add

two

major

divisions

(2

Kcs)

plus

two

sub-divisions

(400

cycles)

as

indicated

on

the

skirt

of

the

tuning

knob.

The

HX-SOO

dial

drive

mechani~m

has

been

machined

to

extremely

close

tolerances

in

manu-

facturing;

however,

there

will

exist

(as

with

all

gear

driv~s)·

a

very

small

error

between

dial

pointer

indication

and

the

tuning

knob

skirt

calibration

when

knob

markings

are

compared

with

the

pointer

indica-

tion

at

various

points

across

the

band.

There

are

several

other

frequency

determining

elements

which

also

contribute

to

the

dial

inaccuracies

such

as:

VFO

tuning

capacitor

and

crystal

tolerances.

As

shipped

from

the

factory

the

"0"

marking

on

the

knob

skirt

has

been

mechanically

aligned

to

the

high

frequency

end

of

all

bands.

Since

most

amateurs

operate

within

a

limited

portion

of a

particular

band,

the

knob

markings

should

be

indexed

for

the

highest

a

ccuracy

possible

in

the

area

of

operation.

To

correct

for

this

knob

runout,

the

knob may

be

PROCE

URE

turned

when

the

pointer

remains

stationary

with

the

aid

of

the

dial

lock.

The

most

accurate

frequency

calibration

means

readily

available

to

the

amateur

is

the

crystal

calibrator

located

in

the

communica-

tions

receiver.

Zero

beat

the

transmitter

as

outlined

below

to

the

nearest

100

Kcs

check

point,

lock

the

dial

by

turning

the

lock

knob

clockwise,

then

turn

tuning

knob

until

"0"

on

the

knob

coincides

with

the

fiducial.

This

will

require

more force or

torque

than

when di

al

is

free running.

CAUTION

The

HX-SOO

Transmitter

has

been

very

conservatively

designed

to

give

reason-

ably

long

vacuum

tube

life.

However,

the

life

expectancy

of

vacuum

tubes

greatly

depends

upon how much

use

and

abuse

they

get.

All

tuning

adjustments

should

be

made

with

the

RF

output

level

meter

indicating

less

than

-10

db

for

conserva-

tive

operation

(with

the

meter

sensitivity

set

at

its

proper

operating

level).

The

final

setting

of

the

RF

level

control

should

be

the

last

tune-up

adjustment

to

be

made.

INITIA

TUNE-UP ADJUSTMENT

The

Operating

controls

should

be

set

as

follows:

FUNCTION:

DSB

OPERATION:

OFF

AUDIO

LEVEL:

o

DRIVER

TUNE:

Set

to

"5"

BAND

SELECTOR:

Set

to

desired

band

FREQUENCY:

Set

to

desired

frequency

CAUBRATE

LEVEL:

Set

to

"s"

METER

SENSITIVITY:

Set

to

"5"

R.F.

LEVEL:

Set

to

"3"

FINAL

TUNE:

Set

to

middle

of

desired

band

segment

VOX

DELAY:

C

ounterc1ockwise

posi-

tion

FSK-FM-~F:

Set

to

middle

of

range

ANTI-TRIP

SENSITIVITY:

C

ounterc1ockwise

posi-

tion

VOX

SENSITIVITY:

Counterclockwise

posi-

tion

ALC

(REAR

APRON):

Clockwise

position

(OFF)

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7

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m

Turn

the

"Operations"

switch

to

Standby

and

allow

at

least

a one minute vacuum

tube

warm-up.

Turn

the

"Operations"

switch

to

MaX

and

adjust

"Driver

Tune"

for maximum

meter

deflection.

Then

adjust

"Final

Tune"

for the

highest

reading.

Repeat

adjustment

of

both

Driver

and

Final

Tune

until

Meter

deflection

cannot

be improved.

CW

OPERATION

Turn

the

"RF

Level"

control

until

the

"Level

Indicator"

reaches

a maximum

(saturates).

Use

the

lowest

setting

of

the

control

consistent

with

obtain-

ing

maximum

output

(knee

of

curve).

Adjust

"Meter

Sensitivity"

control

to

read

"0"

db.

Turn

the

"Function"

switch

to

CW

and

key

the

transmitter

via

the

"Key"

jack.

SIDEBAND

OPERATION

After

the

transmitter

ha s

been

tuned

up

to

a

de-

sired

frequency

on

CW,

adjust

the

"ALC"

control

(on

the

rear

of

the

chassis)

so

that

the

"Level

Indi-

cator"

drops

to

-1 db or one

half

a

division.

Turn

the

"Function"

switch

to

USB or LSB

and

the

"Audio

Level"

control

knob

until

the

"Level

In-

dicator."

meter

fluctuates

or

averages

around

the

-10

db

marking when

talking

into

the

microphone

at

con-

versational

level.

This

setting

will

usually

be 4

to

5

depending

on

the

mike,

speaking

level

and

distance.

VOX

SENSITIVITY

-

VOX

DElAY

-

ANTI-TRIP

OPERATION

After

the

transmitter

has

been

tuned

up

to

the

desired

frequency

with

all

of

the

larger

sized

knobs

adjusted,

the

VOX

Relay

control

knobs

are

brought

into

adjustment.

Turn

the

"Operations"

switch

to

indicate

VOX

and

turn

the

"VOX

Sensitivity"

knob

clockwise

until

the

VOX

relay

readily

closes

when

talking

into

the

,microphone.

It

is

desirable

to

keep

the

"VOX

Sensi-

tivity"

as

low

as

possible

since

any

undesired

background

noise

in

the

Ham

Shack

will

trigger

the

VOX

relay

and

you

will

be

on-the-air.

Usually

the

"VOX

Sensitivity"

knob

will

be

near

the

center

of

its

range

or

pointer

vertical.

The

de-energizing

time for

the

VOX

Relay

is

controlled

by the

"VOX

Delay"

control.

This

control

is

used

to

keep

the

VOX

Relay

closed

during the

quiet

periods

between

words.

Turn

the

"VOX

Delay"

control

clockwise

until

the

relay

flutter

between

words

is

eliminated

during

the

course

of

conversa-

tional

speech.

Excessive

"VOX

Delay"

should

be

avoided.

Leave

at

CCW

position

to

start.

The

"Anti-Trip"

Control

is

used

when

the

"Oper-

ations"

switch

indicates

VOX

operation.

When

the

Page

8

Station

receiver

and

speaker

are

connected

for

VOX

operation

(see

Figure

2)

the

speaker

"Anti-Trip"

control

is

adjusted

to

a

setting

where

the

audio

'signa~

picked

up by the microphone from

the

re-

ceiver's

speaker

will

not

energize

the

VOX

Relay.

This

feature

prevents

the

retransmitting

of the

in-.

coming

audio

signals

from your

station

receiver.

Excessive

speaker

volume

is

capable

of

disabling

the

VOX

Relay

completely,

therefore,

minimum

re-

quired

gain

should

be

used.

Always

adjust

the

receiver

audio

gain

to

the

desired

level

before

ad-

justing

the

"Anti-Trip"

control.

AM

OPERATI,ON

Turn

the

"Frequency"

and

"Band

Selector"

knobs

to

indicate

anyone

of

the

authorized

amateur

phone

bands.

Tune

the

transmitter

for maximum

out-

put

as

outlined

in

the

general

and

CW

sections

with

switches

on DSB

and

MaX.

Reduce

the

RF

Output

level

to

indicate

-6 db on

the

"Level

Indicator".

Increase

the

audio

level

until

there

is

a

small

fluc-

tuation

or

kick

upward in

the

output

level

meter

pointer

when

talking

into

the

microphone.

The

carrier

reference

level

can

be

established

more

precisely

if

an

oscilloscope

and

audio

oscil-

lator

are

used

to

set

up

and monitor

the

output

signal.

If

the

carrier

level

is

set

too

high,

peak

amplitudes

are

flattened

before 100%

modulation

occurs.

If

the

carrier

level

is

set

too

low

the

maxi-

mum

power

output

capabilities

are

not

attained

at

100%

modulation.

FSK

OPERATION

FSK

Operation

is

accomplished

with

the

aid

of V4

(l2BY7)

Reactance

Tube

Modulator

which

shifts

the

frequency

of

the

60

Kcs

Carrier

Oscillator

by

means

of a

change

in modulator

screen

voltage

(see

Figure

3).

Lowering

the

screen

voltage

lowers

the

frequency

of

the

60

Kcs

Oscillator

and

raises

the

RF

Output

Frequency;

conversely,

raising

the

screen

voltage

raises

the

60

Kcs

Oscillator

frequency

and

lowers

the

RF

Output

Frequency.

The

change

in

screen

voltage

is

controlled

by

the

Polar

Relay

keying

employed for

RTTY.

The

amount of

Frequency

Shift

is

adjusted

by

the

FSK

Deviation

control

R140. When the

Polar

Relay

is

closed

the

screen

voltage

on

the

Reactance

Modu-

lator

may be

raised,

lowered,

or

remain

unchanged

depending

on

the

position

of

the

arm of

FSK

Devia-

tion

Potentiometer.

The

zero

position

is

located

at

(approximately)

the

center

of

its

range.

Clockwise

rotation

from

the

center

position

will

decrease

the

s cre

en

voltage

and lower

the

frequenc

y

of

the

60

Kcs

Oscillator.

Counterclo~kwise

rotation

from the

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+150V.

FSK

TO

SF-ID

REAR

(FOR

CW

OPERATION)

PIN

12

ON

J2

AND

P2

PIN 9

ON

J2

AND

P2

R22

I MEG.

R25

200

R

24

330

middle

position

will

increase

the

screen

voltage

and

raise

the

frequency

of

the

60

Kcs

Oscillator.

The

40

cycle

keyed

identification

frequency

shift

is

accom-

plished

by

closing

the

key

jack

contacts.

Note

that

the

40

cycle

keyed

identification

shift

is

not

adjustable

and

when

the

CW

key

Jack

contacts

are

closed

the

screen

voltage

is

lowered

thereby

lowering

the

60

Kcs

Carrier

Oscillator

by

40

cycles

and

raising

the

RF

Output

Frequency

by

40

cycles.

Tune

up

the

transmitter

as

outlined

on

the

preced-

ing

general

and

CW

sections.

Turn

the

Operation

switch

to

Calibrate.

Zero

beat

the

transmitted

signal

in

the

communications

receiver.

Rotate

the

Function

switch

to

indicate

FSK

and

adjust

the

small

"FM-

FSK~F"

knob for zero

beat

if

necessary.

This

ad-

justment

is

made

with

both

Polar

Relay

Contacts

arid

key

Contacts

Open.

Close

Polar

Relay

Contacts

and

vary

the

FSK

Deviation

Control

for

zero

beat,

then

adjust

in

either

direction

from

this

position

for

the

desired

850

cycle

shift.

FM

OPERATtONI

FM

Operation

is

accomplished

by

Reactance

Tube

V4

(l2BY7)

modulating

the

60

Kcs

Carrier

Oscil-

lator.

In

the

FM

position,

the

audio

amplifier

output

is

fed

to

the

screen

grid

of

the

Reactance

tube

there-

by

translating

audio

variations

to

frequency

devia-

tions

of

the

Carrier

Oscillator.

Tune

up

the

transmitter

as

outlined

in

the

preced-

ing

general

and

CW

sections.

Turn

Operation

Switch

to

Calibrate.

Zero

beat

the

transmitted

signal

in

the

communications

receiver.

Rotate

the

Function

Switch

to

indicate

FM

and adj

ust

the

small

"FM-FSK~F"

knob for zero

beat

if

necessary.

Turn

Operations

Switch

to

MOX

and

raise

Audio

Level

until

a

small

fluctuation

of

the

Output

Level

is

observed

on

the

meter.

BIAS

CONTROL

ADJUSTMENT

The

output

of

the

bias

supply

in

the

transmitter

DEV.

~

FOR REMOTE

KEY-40

CYCLE

FSK

CONNECTION

(OPTIONAL)

L-

has

been

set

at

the

factory

to

-50

volts

d.c.

with

117

volts

a.c.

power

line

input.

If

the

line

voltage

is

subject

to

variations,

it

is

advisable

to

monitor

the

plate

current

of

the

6146

vacuum

tubes

and

make

periodic

adjustments

in

the

bias

voltage

to

keep

the

plate

current

at

its

optimum

value.

Adjustments

of

the

bias

supply

will

result

in

extending

the

life

of

the

vacuum

tubes

and

will

provide

maximum

output

power.

Provision

has

been

made

via

the

"External

Con-

nection"

plug

to

connect

a 0-300

milliampere

d.c.

or

a 0-3

volt

d.c.

voltmeter

to

read

cathode

current

on

the

Final

Amplifier

tubes.

The

0-3

volts

d.c.

meter

will

read

0-300

milliamperes

when

connected.

Con-

nect

the

positive

meter

terminal

to

pin

14 of

the

plug

and

the

other

side

of

the

meter

to

pin

13

of

the

plug.

Rotate

the

"Bias

Adj,."

to

read

60

milliamperes

of

plate

current

when

the

equipment

is

in

the

standby,

LSB

or USB

positions.

MODEL

HX-500

USED

AS

AN

EXCITER-DRIVER

WITH

A

LINEAR

AMPLIFIER

The

model HX-500

output

power

is

more

than

ade-

quate

for

driving

a

high

powered

linear

amplifier.

It

may

be

necessary

to

insert

a

resistive

pad

to

absorb

some

of

the

power

output

and

for

the

pQrpose

of

maintaining

a

50

Ohm

load

to

the

HX-500

Transmit-

ter.

The

amount

of

padding

needed

will

depend

upon

the

circuitry

in

the

linear

amplifier

and

the

tubes

used.

Always

use

the

least

padding

necessary

so

that

the

HX-500

is

working

at

well

below

its

maxi-

mum

output.

This

will

result

in

more

linear

operation

overall

and

extend

the

6146

tube

life.

When

the

HX-500

is

used

as

an

Exciter-Driver,

the

RF

Level

Control

is

adjusted

for optimum

drive

on

the

grid

of

the

high

powered

linear

amplifier

instead

of

the

6146's.

Figure

3.

CI63

l,005uF

Simplified

Schematic

Diagram

showing

RTTY

Operation

EXTERNAL

CONNECTION

PLUG

REG

R139

82K

5%

R

140

50K

R

141

22K

5%

-}TO

POLAR

CoRJr'A~\S

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9

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