Hal communications Ak-1 User manual

.,.

....

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******************"k**"'k****************'"**i'\"-k*

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k·l\;'\"1co.Jc-k*'"*"k*·k··kk·k-k***-1<*

WARRANTY

HAL

Communications

Corp.

warrants

that

the

HAL

Communications

Corp.

factory-wired

AK-1

AFSK

Oscillator

shall

be

free

of

defects

in

materials

and

workmanship

under

normal

use

and

service

for

a

period

of

one

year.

Should

such

defects

occur

within

the

warranty

period,

notify

HAL

Communications

Corp.

promptly.

The

warranty

period

is

measured

from

the

date

of

the

original

invoice

to

the

postmar~-date

of

your

notification

letter.

Do

not

return

your

unit

to

the

factory

for

repair

or

adjustment

until

you

have

received

written

return

authorization.

In

the

case

of

AK-1

AFSK

Oscillator

Kits,

this

warranty

applies

only

to

the

parts

supplied

in

the

kit

and

does

not

apply

to

any

wiring

or

components

which,

in

the

judgement

of

HAL

Communications

Corp.,

were

damaged

by

incorrect

use

or

construction

on

the

part

of

the

kit

builder.

This

warranty

is

and

shall

be

in

lieu

of

all

other

warranties,

whether

expressed

or

implied,

and

of

all

other

obligations

or

liabilities

on

the

part

of

HAL

Communications

Corp.

resulting

from

the

installation

or

use

of

this

oscillator.

The

foregoing

warranty

is

completely

void

on

all

AK-l's

which

have

been

repaired

by

individuals

other

than

HAL

Communications

Corp.

personnel,

those

which

have

been

damaged,

abused,

modified,

improperly

installed,

or

tampered

with,

and

those

which

have

been

subjected

to

improper

voltages

or

currents.

*****************************************"'<***·k·k*·k-;'\-1<***"k***"k**'-k*-1<*

1974

by

HAL

Communications

Corp.,

Urbana,

Illinois.

Printed

in

the

U.S.A.

All

rights

reserved.

Contents

of

this

publication

may

not

be

reproduced

in

any

form

without

the

written

permission

of

the

copyright

owner.

...

~

I"'

""

CONTENTS

1.

INTRODUCTION

..

2.

SPECIFICATIONS

.

3.

OPERATION

OF

THE

AK-1

4.

AK-1

KIT

CONSTRUCTION

5.

INTERCONNECTION

OF

THE

AK-1

WITH

OTHER

EQUIPMENT

6.

TEST

AND

ALIGNMENT

....

7.

DIAGRAMS

AND

PHOTOGRAPHS

8.

PARTS

LIST . . . . . . .

ILLUSTRATIONS

Figure

1.

AK-1

Schematic

Diagram . . . . .

Figure

2.

AK-1

Circuit

Board

Layout

....

Figure

3.

Photograph

of

AK-1

Circuit

Board

Figure

4.

Typical

Connections

to

AK-1

...

Figure

5.

Direct

TTY

Keyboard

Connection

to

AK-1

Figure

6.

AK-1

Connection

to

Tube-type

Demodulators

Figure

7.

Direct

Loop

Connection

of

AK-1

Figure

8.

Connection

to

ST-5

Demodulator

Figure

9.

Connection

to

ST-6

Demodulator

Figure

10.

Wiring

Diagram

for

ST-6

Cabinet

.

Figure

11.

Use

of

AFSK

with

a

Typical

SSB

Transmitter

Figure

12.

Spectra

of

Signals

Generated

by

SSB

Transmitter

1

2

3

5

7

13

15

26

16

17

18

19

20

21

22

23

24

25

'

.~

:.

("'\.

"""'

1.

INTRODUCTION

The model

AK-1

AFSK

Oscillator

is

designed

to

generate

tone-encoded

teleprinter

signals

for

transmission

by

either

HF

or

VHF

radio.

Encoding

is

accomplished

by

shifting

the

frequency

of

the

internal

oscillator

from

its

normal

rest

frequency

("mark"

condition)

to

a

higher

frequency

("space"

condition)

as

teleprinter

keying

pulses

dictate.

The

rest

or

"mark"

frequency

output

of

the

AK-1

is

the

standard

2125

Hz

audio

tone

and

the

space

frequency

can

be

selected

to

be

either

2295

Hz

(170

Hz

shift)

or

2975

Hz

(850

Hz

shift).

Additionally,

the

"mark"

frequency

can

be

shifted

upward

by

approximately

100

Hz

with

a

telegraph

key

to

allow

for

CW

identification

of

the

radioteleprinter

transmission.

The

input

keying

requirements

of

the

AK-1

are

compatible

with

output

signals

from

the

HAL

Communications

ST-6

and

ST-5

demodulators

and

can

be

easily

keyed

from

other

sources

of

low-voltage

serial

teleprinter

data

.•

Both

hig~and

low-level

audio

outputs

are

available

from

the

AK-1,

providing

a

great

deal

of

flexibility

in

interfacing

the

oscillator

to

various

radio

transmitter

inputs.

A

five-pole

Butterworth

filter

in

the

output

stages

of

the

AK-1

prevents

generation

of

any

spurious

signals

in

the

form

of

harmonics

of

the

original

audio

tones.

The

entire

oscillator

assembly

is

contained

on

one

2

7/8"

X 5

3/4"

circuit

board,

plugs

into

a 12

edge

connector,

and

requires

only

a

keying

voltage

and

+12

volt

power

supply.

The

AK-1

circuit

board

is

compatible

with

other

circuit

boards

in

the

HAL

ST-6

Demodulator

and

the

AK-1

is

a

common

option

included

in

the

factory-wired

ST-6.

The

HAL

AK-1

AFSK

oscillator

circuit

is

based

upon

a

design

described

by

Irvin

Hoff,

W6FFC,

in

the

February,

1969

issue

of

QST

magazine

(page

11)

.

•

1

.

2.

SPECIFICATIONS

Output

Frequencies:

Mark (170

and

850

Hz

shifts)

Space

(170

Hz

shift)

Space

(850

Hz

shift)

CW

ID

(key

down)

Output

Amplitude:

High-Level

Output

Low-Level

Output

.

2125

Hz

2295

Hz

2975

Hz

2225

Hz

100

mV

rms

20

mV

rms

Frequency

Stability

(after

15

minute

wa~-up)

+ 5

Hz

(all

tones)

Standard

Frequency

Shifts

available

170

and

850

Hz

Input

Keying

Voltage

Requirements:

Mark .

Space

less

than

0

volts,

greater

than

-20

volts

greater

than

+5

volts,

less

than

+20

volts

Power

Requirements

Size

2

. . +12 V de @ 30ma

. 2

7/8"

X 5

3/4"

circuit

board

(7.0

X

14.6

em)

•

J-

0-

~""

""

'•

~

""'

3.

OPERATION

OF

THE

AK-1

The

circuit

of

the

AK-1

AFSK

Oscillator

(see

Figure

1,

page

16)

is

made up

of

five

basic

sections:

oscillator,

keyer,

divider,

filter,

and

output

amplifier.

The

signal

is

generated

in

a

unijunction

relaxation

oscillator

(Q4)

at

twice

the

desired

output

frequency.

The

exact

mark

frequency

of

oscillation

is

determined

by

the

combination

of

C2

and

Rll,

Rl2,

and

Rl3

(also

Rc,

if

used).

The

frequency

of

oscillation

is

changed

from

mark

to

space

condition

by

paralleling

the

Rll,

Rl2,

Rl3

chain

with

either

R6

and

R7

(170

shift)

or

R4

and

R6

(850

shift)

series

resistor

chains.

Therefore,

shifting

from mark

to

space

frequencies

is

accomplished

by

changing

the

charging

time-constant

of

capacitor

C2, a

procedure

that

generates

no

abrupt

phase

discontinuities

in

the

oscillator

waveform.

This

is

a

particularly

important

feature

of

the

AK-1

when

it

is

to

be

used

in

a

SSB-type

of

transmitter

system.

For

ipstance,

oscillator

circuits

that

use

tuned-circuits

will

generate

spurious

signals

due

to

phase

discontinuities

when

shifting

from

mark

to

space.

These

spurious

signals

rarely

cause

problems

in

VHF-type

AM

orFM

applications

but

will

cause

radiation

of

illegal

signals

when

used

with

a

SSB-type

of

transmitter.

The

AK-1

will

not

produce

this

type

of

spurious

signal.

Changing

the

frequency

from

mark

to

space

is

accomplished

electronically

by

keyer

stages

Ql and Q2. Keying

voltages

are

presented

to

6

of

the

edge

connector

with

the

convention

that

for

mark

condition

the

voltage

should

be

zero

or

less

(preferably

between

-5

and

-15

volts)

and

greater

than

+5

for

space

condition.

Therefore,

during

mark,

Ql

is

"off"

as

is

Q2

and

the

effective

charging

resistor

for

C2

is

only

the

Rll,

Rl2,

and

Rl3

series

chain.

During

space,·both

Ql

and

Q2

are

turned

"on",

paralleling

either

R4

and

R5

or

R6

and

R7

(depending

upon

which

is

selected

by

Sl)

with

the

Rll,

etc.

chain.

A

separate

keyer

transistor,

Q3,

is

provided

for

CW

identification.

When

7

of

the

edge

connector

is

grounded,

Q3

is

biased

"on"

and

R8

is

placed

in

parallel

with

the

Rll,

etc.

chain,

increasing

the

frequency

by

approximately

100Hz.

Note

that

this

stage

can

be

activated

at

any

time

and

it

is

therefore

important

that

the

key

(or

its

shorting-bar)

not

be

closed

during

RTTY

transmission.

R8

has

been

chosen

to

give

approximately

100

Hz

shift

from

the

mark

tone,

but

the

exact

amount

of

CW

ID

shift

can

be

adjusted

by

changing

the

value

of

this

resistor.

It

is

important

to

note

that

both

space

tone

and

CW

ID

frequencies

are

determined

by

their

respective

resistor

chains

in

parallel

with

the

mark

resistor-chain.

Therefore,

it

is

necessary

that

the

mark

frequency

be

adjusted

first

since

any

change

in

this

resistor

chain

will

affect

all

other

tones.

To

allow

compensation

for

the

wide

range

of

possible

variation

of

the

unijunction

oscillator

transistor,

Q4,

and

timing

capacitor

C2,

both

a

fine

and

coarse

adjustment

are

provided

for

the

mark

frequency.

The

ranges

of

all

potentiometers

have

been

chosen

so

that

it

should

always

be

possible

to

adju.st

to

the

correct

frequencies

without

changing

fixed

resistors

if

the

unit

is

constructed

correctly.

3

The

output

of

the

oscillator

across

resistor

R22

is

a 2

volt

spike

at

twice

the

desired

output

frequency.

The

divider

stage

(BSMV),

Q5-Q6,

is

triggered

by

these

pulses.

The

output

of

the

divider

(measured

at

the

collector

of

Q6)

should

be

a

square-wave

of

approximately

10

volts

peak-to-

peak

amplitude

and

with

a

frequency

equal

to

the

desired

output

frequency

(2125Hz

for

mark

with

key-up).

The

low-pass

filter

removes

all

but

the

fundamental

component

of

the

square-wave,

resulting

in

a

sinusoidal

output

waveform.

R24

is

the

input

terminating

resistor

for

the

filter

and

R23

is

a

divider

to

reduce

the

voltage

output

and

provide

some

isolation

between

the

divider

and

filter.

If

desired,

the

output

of

the

AK-1

can

be

increased

somewhat by

reducing

the

value

of

R23,

but

care

should

be

taken

to

maintain

the

same

parallel

equivalent

of

R23

and

R24

to

keep

the

proper

filter

termination

impedance.

Since

it

is

only

necessary

that

the

filter

provide

rejection

of

the

harmonics

of

the

divider

output

(odd-order

harmonics

for

the

square-wave),

the

filter

does

not

require

critical

timing

and

can

be

assembled

directly.

If

problems

are

suspected

with

the

filter

circuit,

the

pass-band

can

be

checked

by

removing

the

end

of

resistor

R23

from

the

collector

of

Q6

and

substituting

an

audio

oscillator,

observing

the

output

across

C7. The

filter

should

be

"flat"

(within

1.

0 dB) up

to

3000

Hz

and

should

be

of

the

order

of

13

dB

down

at

4250Hz

(2 X 2125)

and

31

dB

down

at

6375

Hz

(3

X

2125).

This

check

is

not

normally

required

and

should

only

be

necessary

if

problems

occur.

Two

outputs

are

provided

from

the

AK-1:

an

attenuated,

high-impedance

output

of

20

mV

rms

for

typical

connection

to

the

high-impedance

microphone

input

on

a

transmitter,

and

a

500

ohm, 100

mV

rms

output

that

can

be

used

for

carbon-microphone

inputs,

to

drive

counters,

and

other

high-level

applications.

Transistor

Q7

is

used

as

an

emitter-follower

isolation

amplifier

to

drive

the

100

mV

output.

When

connecting

to

the

100

mV

output,

it

should

be

remembered

that

the

coupling

capacitor,

C9,

is

electrolytic

and

leakage

inherent

in

any

electrolytic

will

produce

a de

voltage

if

a

very

high

impedance

device

is

connected

to

this

output.

This

is

particularly

true

of

some

counter

input

circuits

and,

on

counters

without

a

blocking

input

capacitor,

can

cause

false

counting.

The

cure

is

to

terminate

the

output

in

lK

to

lOK

ohms.

Another

precaution

for

use

of

the

100

mV

output

is

to

maintain

fairly

low

shunt

capacitance

across

the

output.

Under some

conditions,

transistor

Q7

will

oscillate

in

the

5

to

10

MHz

range

if

the

100

mV

output

is

capacitively

loaded.

The

cure

is

to

reduce

the

capacitance

of

the

load,

or

use

ferrite

beads

on

the

leads

of

Q7. Use

of

resistor

Rx

to

provide

space-tone

pre-emphasis

is

discussed

in

detail

in

the

applications

section

of

this

manual.

Power

required

by

the

AK-1

is

connected

to

pins

5 (+12V @ 30

ma)

and

1

and

12

(ground

return).

An

additional

zener

regulator,

D3,

provides

+8.2

volts

regulated

to

the

oscillator

circuit,

but

regulation

of

the

+12

volt

input

is

also

highly

recommended.

4

~

,....,(

\,

4.

AK-1

KIT

CONSTRUCTION

Construction

of

the

AK-1

involves

two

steps:

assembly

of

the

circuit

board

and

interconnection

of

the

circuit

board

to

a power

supply,

control

switches,

connectors,

and

the

rest

of

the

RTTY

system.

Since

there

are

many ways

in

which

the

AK-1

may

be

interfaced

with

other

equipment,

a

number

of

common

interconnection

schemes

are

presented

and

discussed.

The

constructor

should

familiarize

himself

with

all

techniques

discussed

and

then

choose

the

one

that

is

most

convenient

for

his

particular

system.

Obviously,

the

circuit

board

must

be

assembled

in

any

case

and

this

task

may

be

tackled

first.

4.1

Circuit

Board

Construction

of

the

AK-1

involves

~ssembly

of

most

of

the

parts

on

the

circuit

board

and

then

installation

of

the

board

and

its

edge

connector,

switch,

and

connectors

in

whatever

housing

the

constructor

chooses.

Assembly

of

the

circuit

board

is

quite

simple

and

will

generally

not

require

more

than

one

hour

of

construction

time.

The

circuit

board

layout

in

Figure

2

and

the

photograph

in

Figure

3

(pages

17and

18)

should

be

closely

followed

for

correct

parts

placement.

The

following

assembly

order

is

recommended

for

the

circuit

board.

First,

mount

all

of

the

resistors

on

the

circuit

board,

starting

with

the

four

trimming

potentiometers.

Note

that

each

has

different

resistance

-

locate

the

proper

location

for

each

before

soldering

it

in

place.

The

~

watt

fixed

resistors

can

now

be

mounted

in

the

locations

indicated.

ALL

resistors

are

mounted

in

a

vertical

position

with

the

body

of

the

resistor

placed

over

the

hole

marked

with

a "V"

on

the

circuit

board

layout.

Resistor

locations

marked

"Ra",

"Rb",

and

"Rc"

are

provided

for

series

trimming

resistors

if

required.

They

are

generally

not

required

and

jumpers

should

be

inserted

in

these

locations

initially.

If

trimming

resistors

are

found

to

be

required

upon

alignment,

the

appropriate

jumper

can

then

be

replaced

by

a

series

resistor.

Resistor

"Rx"

location

is

provided

to

allow

a

limited

amount

of

"pre-emphasis"

on

the

space

tone.

Choice

of

this

value

depends

~pon

the

equipment

that

the

AK-1

is

used

with

and

this

location

should

be

left

open

until

tests

indicate

what

value

is

optimum.

Choice

of

~

values

is

discussed·

in

the

alignment

and

test

section

of

this

manual.

The

transistors

and

diodes

should

now

be

mounted,

being

very

careful

to

observe

correct

transistor

orientation

and

diode

polarity.

Note

that,

as

with

the

resistors,

ALL

diodes

are

mounted

in

a

vertical

position

with

the

body

of

the

diode

over

the

hole

indicated.

Place

the

capacitors

on

the

circuit

board

next,

starting

with

the

ceramic

and

mylar

capacitors

first.

When

mounting

the

electrolytics,

observe

the

polarity

marked

on

the

layout.

All

electrolytic

capacitors

are

mounted

in

a

vertical

position

with

the

body

placement

indicated

as

before.

The

.01

~f

polystyrene

capacitor

should

be

mounted

horizontally

in

the

position

indicated.

5

"\

The two 88

mhy

toroidal

inductors

should

be

mounted

last.

The two

halves

of

each

toroid

are

connected

in

"series-aiding"

with

the

"loose-end"

of

one

half

connected

to

the

"sleeved-end"

of

the

other

half

to

form

the

center-tap.

Fasten

the

toroids

to

the

board

with

the

6-32

hardware

furnished

with

the

kit.

The

correct

order

of

assembly

is:

screw-head,

flatwasher,

nylon

washer,

toroid,

circuit

board,

lockwasher,

and

6-32

nut.

The

completed

assembly

should

have

the

screwhead

and

toroid

on

the

component

side

of

the

circuit

board.

This

completes

the

assembly

of

the

circuit

board

and

it

should

be

set

aside

until

the

switch,

connectors

and

power

supply

have

been

mounted.

4.2

Installation

of

the

Circuit

Board

Since

the

AK-1

is

designed

to

be

used

in

conjunction

with

other

RTTY.

equipment,

it

does

not

have

a

self-contained

power

supply

and

must

therefore

be

furnished

with

+12

volts

de

at

30 rna.

This

voltage

can

be

obtained

from

the

demodulator

(such

as

the

ST-5

or

ST-6)

or

other

low-voltage

source.

Whatever

the

source,

the

+12

volts

furnished

to

the

AK-1

should

be

well-

filtered

(free

of

hum

and

noise)

and

reasonably

well

regulated

(zener

regulation

is

quite

adequate).

The

circuit

board

of

the

AK-1

should

be

mounted

in

a

metallic

container

(for

shielding),

away

from

obvious

heat

and

hum

sources.

When

the

AK-1

is

used

with

the

ST-6,

a

circuit

board

location

has

been

reserved

in

the

de-

modulator

cabinet

for

the

AFSK

oscillator.

A 12

edge-connector

is

supplied

with

the

AK-1

kit

to

make

connection

with

the

circuit

board,

but

this

can

be

deleted,

if

desired,

and

connections

made

directly

to

the

circuit

board

at

the

extra

pads

provided.

This

technique

will

allow

the

fingers

of

the

board

to

be

cut-off,

saving

approximately

3/4

inch

in

overall

length

(fingers

plus

edge

connector).

Also

supplied

with

the

kit

are

two phono

pin-jacks

for

audio

output

connections

and

two

~"

phone

jacks

for

hand-key

and

RTTY

keying

signal

input.

A

DPDT

toggle

switch

is

provided

to

change

the

shift

of

the

AK-1.

Since

the

AK-1

requires

only

one

pole

of

the

switch,

the

other

pole

may

be

utilized

to

change

the

demodulator

shift

or

other

function

as

desired.

Typical

connections

to

the

AK-1

are

shown

in

Figure

4.

6

Hal Communications AK-1 User manual

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