Massive Audio DB8000 User Manual download pdf (Page 64)

Although t ' does look like a "tuned

line"

problem, there

a chance that the

signal

may be so strong that the tape re-

corder preamplifier and phono amplifier are

giving you

partial rectification of the ham

signal. You

can cure such a condition by

inserting

75,000

-ohm

resistor in

series

with

the control

grid of your tape recorder

preamplifier. Bypass

each

of the grids to

ground through a small -value (0.001 -µF)

ceramic

capacitor.

Unlike

tube

-type

ampli-

fiers, most

transistor amplifiers

do not

have

the tendency to

pick

up r.f. signals.

Upgrading

the National NCX -3. I have just

purchased a second -hand

NCX -3

transceiver

and would

like to know if there is anything

1 can do to

improve

its performance?

Generally

speaking, when the

NCX

-3 is

operating

up to snuff, there is little

you can

do to

improve performance. However, there

are some

cases where better drive can be

achieved without

too much difficulty.

First, remove

the 12BY7

driver

tube

and

replace

it with a 6GK6. The filament con-

nections

must be rewired as shown

in Fig. 2.

Using your instruction

manual, first locate

R -11.

Change the value of

this resistor to

100

ohms,

1 watt. Change resistor R -13 to

100,000

ohms, 1/2 watt. Remove the ground

connection

from pin 3 of

V -4

and change

(V4)

(V3)

6BE6 6GK6

izV

12f1

cow

Fig. 2. Filament rewiring in NCX

-3.

V -4 to a 6BE6

tube. Locate the

brown wire

going from pin

4 of V -4 to pin 5

of V -3.

Remove

the wire from pin 4 of V -4 and re-

connect this

wire to pin

of V -4. Connect

-ohm,

10 -watt resistor from pin 4 of V -4

to pin 5 of

V -3. Now repeak

all

driver and

mixer

coils.

Telephone

Pickup. I would like

to make

my own inductive telephone pickup. Or,

if it would be too

much work, is

there any

particular one that you

could

recommend?

A telephone pickup

is nothing

than

small induction coil.

You can

make your

own by

winding 500 turns

No. 40

AWG

enameled

wire

21 -inch length

of l,4 -inch

round or square soft iron stock. Glue

small suction

cup to

one end

the iron rod

and connect the

induction

coil

to your tape

recorder or amplifier through

a shielded

lead

-the

lead must be

grounded.

However,

why bother to go to all this trouble? You

can get a good pickup for $1.19 from

La-

fayette

Radio Electronics (99 C 6197), and

top

-quality

pickup is

only $1.80 (28

7094).

Allied Radio's phone pickup

(15

8354) at $1.80 and

Burstein

-Applebee's (17

A 811)

$1.69 are

also suitable.

Applying for

CB License.

What hap-

pens if I accidentally make a mistake in my

FCC Form 505

when

filing

for

a CB station

license?

There's a very small chance that you will

make an error

you follow the details out-

lined

in the 1967 COMMUNICATIONS HAND-

BOOK. This Handbook is now

on most news-

stands and

the chapter on how

to prepare

your license application was written

Peggy

Ploger, KLJ8033. However, if by any chance

you do make a mistake, the Form

505

will

returned to you and you must reapply -and

send them another

$8 application fee.

Hi-Fi Speaker

Mismatch.

I have

a top -

quality hi -fi speaker made in Europe

and I

notice that the

voice

coil is marked

ohms.

Can I use this in conjunction

with my hi -fi

amplifier which only has a 8 -ohm

and 16-

ohm output?

Generally, a 3 -ohm

mismatch

-presuming

that

you

would connect the 5 -ohm

speaker

to the 8 -ohm terminals -will have an insig-

nificant effect on

the reproduction

quality.

It all depends on the

amount of feedback

within the amplifier itself ; if

the feedback

level is too low,

you

may encounter

some

loss in efficiency.

course, the whole

problem would be solved if your

amplifier

had

4 -ohm

output connection.

CB Rig

Repairs.

had some trouble

with

the

transmitter portion of my

CB base

sta-

tion.

A friend tried to fix it, but

a couple

days later a fellow CB'er told me I

was off

frequency. I took the rig to a service

shop,

and

they

charged me $27 for

one crystal,

transmitter

alignment, and frequency

check.

Isn't this too

much?

No,

it's

just

about right. For

the

expert

service

required in setting up

a CB base

station,

you can expect a bench charge

of at

least

$9 per

hour. However,

always make

sure you

have a signed slip from

the ser-

vice shop indicating what has been

done to

your CB

rig. You will need

this as an

ex-

hibit

if the FCC should

find

that you're still

off

frequency.

What

Have We Here? A wise

guy in my

neighborhood has started

using

the

expres-

sion

"myriametric

waves." What are

they -

plasmonics

in disguise ?"

Nope, just

plain old radio waves

in the

spectrum from 3 to

30 kHz, or 100,000

down

10,000 meters. Plans

for

building a re-

(Continued

on page 101)

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