Operating instructions

ManualsBrandsSharp ManualsMicrowave OvenR-309B

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MULTIPLIER FACTOR.

Figure

4-6.

Harmonic-Generator

Board,

Block

Diagram

from

14 l\IHz to 28 l\IHz.

This

frequency

range

is

doubled

by

CRI

and CR2

and

amp-

lified

by

tuned

amplifier

Q3, to

achieve

a

signal

in

the

range

of

from

28 MHz to

56 MHz.

This

signal

is

matched

by

emitter

follower

Q4 to

the

10\\

'

imped

ance

of

ste

p-recovery

diode

CR4.

The

step-

recov

ery

diode

condu

cts

during

the

positive

half

of

th e

input-sign

al

and

stores

that

charge.

Durin

g

the

negative

half

it

is

quickly

driven

towards

cutoff

and

snaps

back

to

form

an

extr

emely

n

arrow

pulse

that

is

rich

in

harmoni

cs

.

The

fundament

al

frequency

output

is

28 MHz to 56 MHz and

the

h

armonic's

are

usable

to 1150 MHz.

These

pulses

and

the

resulting

harmonics

form

the

LO

signal.

See

Table

4-1.

The

board

output

feeds

coaxi

al

relay

CH-K1.

Diode CR3

rectifies

a

sample

of

the

fundamental

frequency

r an

ge

of

the

harmonic

gen

er

ator

th at

is

filtered

to

form

the

dc

tuning

vol

ta

ge

which

drives

the

FREQUE

NCY

meter

when

the

harmonic

am pl

ifi

er

is

being

tun

ed by

the

variable

capacitors

(C5). Th e ca

pacitors

are

con-

nected

to

the

HARl\I. A!\IP. TUNING

control.

Transformers

Tl,

T2, and

T3,

and

the

trimmer

capacitors

(C6) ar e

adjusted

such

that

the

tuned

amplifiers

linearl

y

follow

(track)

the

manual

tuning.

The

Channel

Frequency

Chart

(T

able

4-1)

provides

a

means

to

determine

the

crystal

frequency

when

the

channel

fre-

quency

is

known.

Locate

the

applicable

ch

annel

frequency

range

in

the

CHANNEL

FREQUENCY

RANGE

column.

Add

or

subtract

10 MHz

as

indicated

in

the

ADD

OR

SUBTRACT

10 MHz

column

to

deter-

mine

the

first

LO

frequency

re-

quired.

Th e

resultant

frequenc

y

should

be

within

the

rang

e

in

the

LO

FREQUENCY

RANG E

column.

Divide

the

LO

frequency

by

the

number

given

in

the

DIVIDE BY

column.

The

resultant

fre-

quency

is

the

crystal

frequency

required

and

should

be

within

the

range

in

the

CRYSTAL

FREQUENCY

RANGE

column.

Example:

153.123

MHz -

Assigned

frequency

10.

000 MHz

Subtract

143

.123

MHz

1st

LO

frequency

143.123

+ 18

Divide

by

7,951.277

kHz

Crystal

frequency

4-9

5601"0015"1