Metra Electronics DAT Combo Instrukcja Użytkownika Pobierz pdf (Strona 48)

where

it

can be

transferred

to

tape in an

unedited

version

of what

was

said.

As

shown

in the

photographs,

the Tie -Spy

consists

of

an

miniature,

very-

short

-range

FM

transmitter

and

a

microphone

that

ap-

pears

to

be a high

-class

diamond

-studded

tie -pin.

You

simply

clip the mike

to your

tie

(naturally you're

out

of luck

if you wear

bow

ties), place

a battery

in the

transmitter,

and

you're on

the

air. A nearby

confederate

can monitor

your

conversation

on an FM

portable

and handle

the

recording.

Construction.

The

unit shown

is housed

in a plastic

case

approximately

21/s

x 11/4

x

13/4 inches. Actually

it

can be made

smaller

by

using

subminiature

components.

But

to

keep

the

price down

to rock bottom, we

have

used

standard

components

available

from Allied

and Lafayette

Radio (among

others).

If you want

to squeeze it into

an

olive

by all means

do

so,

just

use

the equiv-

While the fie

-bar may not

be the most

in

men's

jewelry it

does the

job -it's

the

mi-

crophone that

counts

the most

right

here.

aient

miniature values-

nothing

is

really

crit-

ical

except the

coil.

In

a similar vein,

the

sound quality

is

exceptionally "tinny

" -readable

but

"tinny."

This

is

due to

the low-

impedance

loading

of

the high

-impedance

crystal tie -clip mike

we

used

to keep

costs down.

If you want

to go

for

a few

extra bucks

get

a

better

mike,

a

low impedance

job -say

a dynamic

type

from 500

to 500

ohms. You

can

even try

a

small

transistor

radio speaker,

or might

even

add a

matching

transformer.

As we

said,

nothing

is

really

critical.

The

electronics

is assembled on

a 15 /s

x

no inch

section of perf- board. If you

slight-

ly

round

-off

the corners the perf -board will

just

fit

into

the

plastic case.

Start assembly

by

mounting

tuning

capaci-

tor C5

and

oscillator

/antenna

loading

coil

Ll. L1 is made

as follows: Cut off

a three

foot section

of AWG

-18

solid

enameled

wire

and tensilize it by clamping one end

in

a

vise

and pulling on the free

end until the

wire goes "dead

slack " -unless

this is done

52

the

coil

will

unwind

when

you

release

ten-

sion.

Using

a 3/4-inch

drill bit

as the

form,

wind

seven

closewound,

tight

turns.

Remove

the

coil from

the

form

and stretch

the first

three

turns

so the

distance

from

the

"start"

to the

third

turn

is

exactly 3/4

inch.

Scrape

a

small

bit

of insulation

from

the start

of the

third

turn (actually what

we

call the

second turn),

and solder

about

an

inch

of wire

to this

TAP

24-

INCH

ANTENNA

Coil is

quite

critical since it

determines the

transmitting

frequency.

It

must be right

on

the

button.

tap.

As shown

in

the

schematic,

the tap

con-

nects

to

the

"top"

of

C5

while

the "start" of

the

coil connects

to Q2's

collector. The

free

end

of

the coil will

be connected

later to

the

antenna.

Flea

clips or Vector

T28 push

-in

terminals

are used

for

tie points

and supports.

To

mount

the

C5 -L1 assembly,

push

in a set of

terminals

directly under

C5's

solder tabs

and

install

a

very

short support

lead

from C5's

tabs

to the terminals.

To insure

frequency

stability

C6

should

be the silver

mica type

or its

equivalent.

Space

gets a little

tight on

top of

the

board

so

miniature

resistors

(Mo or

1/s

watt)

and

capacitors

are suggested.

The

components

on

the bottom

of the board

can be "standard"

size

(1/4 -watt resistors,

etc.).

We

can

only

be

certain the

project will

work with

the transistors

specified

in

the

parts list, do not

substitute

another

type for

the specified QI

and

Q2.

Battery

Power.

The

power

supply has no

R5

C4

Either

1/10 or 1 /2 -watt resistors

can

be

used here

on under

side of perf-

board.

RADIO

-TV EXPERIMENTER

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