Ten-Tec 243 - Page 4

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3-243

ACCESSORIES

COUNTER

THEORY

OF

OPERATION

The

PTO

subassembly

in

the

Model

243

is

identical

to

that

used

in

the

@MNI.

In

addition

to

this

assembly,

automatic

and

manual

switching

circuits

for

supply-

ing

the

operating

voltages,

a

crystal

oscillator,

buffer,

and

a

switched

amplifi-

er

are

contained

on

three

additional

assemblies.

CONTROL

ASSEMBLY

80504.

This

board

provides

a

pair

of

secondary

switched

R

and

T

Voltages

to

determine

which

of

two

signal

sources

controls

the

frequency

of

the

@MNI.

T

voltage

from

the

@MNI

is

used

to

produce

two

control

voltages

À

and

B,

which

are

routed

through

the

MODE

switch

to

select

the

desired

mode

of

control.

The

MODE

switch

wafers

are

located

on

this

board.

The

signal

bufíering

and

switching

are

done

on

the

AMP/SWITCH

board

80505.

The

A

and

B

voltages

are

used

to

switch

the

PIN

diodes,

D1

through

D3,

which

do

the

actual

signal

switching

in

conjunction

with

controlled

common

base

amplifi-

ers

Ql

and

Q2.

The

selected

signal

is

buffered

by

amplifier

03

and

routed

to

the

®MNI.

When

crystal

control

is

desired,

the

XTAL/OSC

board

80506

is

used.

This

board

contains

all

of

the

switch

wafers

associated

with

the

REMOTE

switch.

When

one

of

the

XTAL

positions

is

selected,

the

B

control

voltage

is

routed

to

PIN

diode

D3,

the

Model

243

PTO

is

turned

off,

and

operating

voltage

is

applied

to

the

oscillator

FET

Q4.

The

four

crystal

sockets

and

their

associated

trimmer

capacitors

are

located

in

the

center

of

this

board.

ALIGNMENT

AND

SERVICING

Please

refer

to

the

ØMNI

Owner's

Manual

for

specific

information

on

measur-

ing

voltages,

removing

plug-in

assemblies,

etc.,

which

appears

on

Pages

3-1

through

3-4.

XCVR

RX TX

REMOTE

XTAL/OSC

.

80506

CONTROL

80504

b

©GND

+REG®

PTO

HREGO

AMP/SWITCH

PGND

VFO

80505

MODEL

243