Boss Audio Systems BV8.5GA User Manual download pdf (Page 64)

dB, we

had to

supply

5500

input,

which

is actually

50 dB

over the

input

and 43dB

over the

input.

Comment.

The

Drake

Model

SPR -4

receiver, in

spite of its deceptively

simple appearance,

a highly

sophis-

ticated

unit. It is

not to

confused

with the many

low- priced

"communi-

cation receivers"

directed

toward

the

young

SWL and novice

ham. It may

simple

enough

to be

operated

be-

ginners,

but it is

obviously

meant

forthe

advanced

SWL,

while

also offer-

ing

excellent

flexibility

for the

inter-

mediate

and

advanced operator.

The

SWL in

search of

an elusive

station can

set

the

dial to the

station's

frequency

with complete

assurance

that

he is tuned

to what the

dial

says.

addition, if his

antenna and propaga-

tion

conditions

are right,

he will

surely

hear

the

station he is

after -assuming,

of course, it is

on the

air.

If you plan

to buy the Model

SPR

-4

receiver,

we feel

you

should

seriously

consider

including

the

optional

crystal

calibrator

in your

order. With-

out

it, the receiver

will probably

tuned to

within

kilohertz

the

indi-

cated frequency,

but why

settle for

that

when it can

the nose

CIRCLE

NO.

READER

SERVICE

CARD

AMERICAN

CIRCUITS

SYSTEMS

MODEL

MK1

FUNCTION

GENERATOR

Sine, .square,

triangle

waveforms

from

6 Hz to beyond

1.25 MHz

THANKS

to low -cost integrated

circuits

and

new

approaches in

design,

very important

change is

tak-

ing

place

audio (and digital)

signal

generators.

Until fairly recently,

audio

signal generators

simply

provided

sine

and

square waves that were vari-

able in level

and covered

a frequency

range

of about

100,000

Hz.

The new "function"

generators

that

have

begun to make

their

appearance,

by contrast, provide

sine, square,

and

triangle (or ramp)

waves over

range

of about

Hz to 1 MHz

and

beyond.

One

good example of

a low -cost

function

generator

is the

Model

MK1

made

American

Circuits

& Systems,

Inc.

The MK1

sells for $135 in

kit

form.

It is

also available factory -wired,

tested,

and adjusted for $195.

The Model

MK1 function

generator

features

sine

square -,

and

triangle

wave outputs that

are selectable

by a

WAVEFORM

switch.

The

waveforms,

available

at a pair of

color -coded

bind-

ing posts

on the front

panel,

are

con-

tinuously

variable

from 0

volts

peak -to

-peak via

AMPLITUDE

con-

trol. Another

control, labelled

ATTENUATE,

can

be used to provide 0,

20,

dB or

attenuation.

Built

into the

instrument

is a dc

OFFSET

control that permits the

signal to be dc

biased anywhere from

+10

to 10 volt

into

an open

circuit

( ±5 volts

into 600

ohms).

Selecting

frequency

a two -step

process: First,

the RANGE

switch

must

set

to the

desired

position (X10,

X100, X1K,

X10K, X100K).

Then,

the

FREQUENCY

control,

calibrated

equally

spaced increments from

0.9 to

11,

set for the

desired

frequency.

Hence,

you

wanted

50007Hz

output

frequency,

you

would

set

the

RANGE

switch to X1K

and the

FREQUENCY Con-

trol to 5. (The

actual

range

the MK1

is from less

than

to beyond 1.1

MHz.)

On the rear panel

the

instrument

TTL

output jack that provides

TTL -compatible

signal of the

same

frequency

that

the

OUTPUT bind-

ing posts

on the front panel. The

logic -0 and logic -1 levels of this

signal

are

and

volts, respectively.

(CMOS

logic

can be driven directly

from the OUTPUT binding posts.)

Also

on the

rear

panel is a

vCO

input

jack

that virtually doubles the versatil-

ity

the function generator. With the

appropriate inputs applied to this

jack,

the output can be

swept

through

range

frequencies,

be frequency

modulated

with tone or voice,

or be

frequency

shift

keyed.

Within the

instrument itself

are six

IC's, two

which

are precision volt-

age

regulators,

with the remainder

being

linear

devices. The power

sup-

ply employs

circuit

-protecting

fusing

and operator -protected three

-con-

ductor line cord.

Kit Details.

selected

the Model

MK1 function generator

kit for

our

test

report. Upon opening the

carton in

which it

arrived,

we were

gratified to

note that

all components were

of pre-

mium quality. Most

of the resistors,

even

some

in noncritical parts

the

circuit,

were

5- percent

tolerance,

while the trimmer potentiometers

that

serve as hidden set

-up

controls were

of OEM quality. The

large printed cir-

cuit board on which the majority

the

components

are

mounted

is made

from

G -10 epoxy fiberglass.

Assembly is

simple and straightfor-

ward,

guided

by clear step -by -step

instructions

and detailed

drawings.

The

only test

instruments

needed

put the function

generator

into

service

order

are

multimeter

(for

the

voltage

checks)

and an oscilloscope

(for

dis-

tortion

adjustments).

frequency

counter

comes

in handy,

but is not

necessary,

for

calibration.

(Three

methods

of calibration

are detailed

the instructions.)

Using the

scope, the

sine -wave distortion

can

be set within

a few percent

of optimum, while

it can

be fully

optimized

with the

aid

of a

distortion

meter.

After Assembly.

Once

the function

generator

was ready to

be put into

ser-

vice, we

subjected it to

a few tests.

Using a precision

frequency

counter,

we determined that

its frequency

range

was from 6 Hz to 1.254

MHz in

five

overlapping bands.

The

FRE-

QUENCY control's dial calibration was

well within the

specified

±5- percent

figure

over almost

the

entire

range.

The

amplitude of the output

signals

could

be adjusted from 0 to

slightly

more than 20

volts peak -to

-peak, while

the dc offset was

adjustable to its

specified

±10

-volt limits into

an open

circuit.

Triangle

waveform linearity

was

better

than 1 percent

between 10

and

100

kHz

and about

2.8

percent

maximum

from

100

kHz to 1 MHz.

Without

using

a distortion meter,

the

distortion

the

sine -wave function

averaged

an excellent 6 percent.

When

a distortion meter

was

used, the

figure

could

be optimized

2.4 per-

cent. All

other

specifications were met

or exceeded.

Comment. The American

Circuit

Systems Model MK1 function

gener-

ator

an excellent buy, particularly

in kit form. It

offers a quality

and versa-

tility that

should appeal to the

audio or

digital experimenter and service tech-

nician.

CIRCLE

NO.

READER

SERVICE

CARD

POPULAR

ELECTRONICS

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