AEA MBA-RC User guide

Price: $5.00

INSTRUCTION MANUAL

AEA Morse-Baudot-ASCII Reader/Code Converter

Model MBA-RC

Copyright 1982 by ADVANCED ELECTRONIC APPLICATIONS, INC.
All rights reserved. No part of this book may be reproduced or
utilized in any form or by any means, without permission in
writing from the publisher.

INSTRUCTION MANUAL

AEA Morse-Baudot-ASCII Reader/Cose Converter

Model MBA-RC

Congratulations on your decision to purchase the AEA Morse-

Baudot-ASCII Reader/Code Converter. This equipment is extremely

versatile and will provide many hours of enjoyment to you.

The MBA-RC has two primary functions. It will read Morse code,

Baudot and ASCII RTTY (Radio Teletype). It will also allow you

to transmit Morse, Baudot or ASCII via hand key, electronic

keyer, or a keyboard.

There are a number of secondary functions available. You may

transmit cross mode. For example, if you have only CW cap-

ability you can still work a RTTY station either via Baudot or

ASCII.

The MBA-RC provides a visual monitor for your message trans-

missions as well as visual copy of stations received on a com-

munications receiver.

The unit is compact and easily assimilated into an average

amateur station. It requires only 13 VDC at approximately 1.5

Amps for operation, making it ideal for both fixed and portable

two-way RTTY operation.

TABLE OF CONTENTS

Front Panel Description....................1

Rear Panel Description ....................2

Hook-Up Instructions (Rear Panel Connector Guide).......3

Rear Panel Connections - Block Diagram ............7

Front and Rear Panel Controls.................8

Illustration 1. You work Morse; Other Station Baudot . . 9

Illustration 2. You work Baudot 60 WPM; Other station

ASCII 110 Baud ............ 11

Illustration 3. You work 110 Baud ASCII; 0ther station

Morse ................ 12

Illustration 4. You work Morse; other station ASCII

110 Baud ............... 13

Illustration 5. You work Baudot 60 WPM; Other station

Baudot 100 WPM ............ 14

Illustration 6. You work Morse; Other station Morse . 15

Illustration 7. You work ASCII 300 Baud: 0ther station

ASCII 110 Baud ............ 16

Illustration 8. You work Baudot 60WPM; Other station

Morse ................ 17

Illustration 9. You work ASCII Baud with Terminal

other station Baudot 100WPM ..... 18

Monitoring Morse Code.................... 19

Input/Output Indicator Lights................ 20

Use of I. D. Control .................... 20

The Filter Control ..................... 22

Carriage Return/Line Feed.................. 22

Normal/Reverse Switch.................... 23

Buffer ........................... 23

Power Switch ........................ 24

Check-Out for CW Reception and Transmission......... 24

Check-Out for Baudot Reception and Transmission....... 27

Check-Out for ASCII Reception and Transmission ....... 29

The Loop Supply 60 and 20 mA Schematics........... 31

Parallel and Serial Connections............... 32

Symbols used in TTY..................... 33

Parts Pictorial and Schematic Diagrams ........... 34

Parts Lists......................... 40

Technical Specifications and Limited Warranty........ 44

FRONT PANEL DESCRIPTION

32 character vacuum
Fluorescent Display

Input selection Output selection
switches switches

1

RTTY-CW Power Switch
Filter
selection To reverse mark

and space frequencies.

(Used for “inverted”
Tuning stations or RTTY copy
Bargraph on USB)

CW Speed Set
Variable Shift and I.D. Buffer
Control Control

Carriage Return
and Line Feed
Control

REAR PANEL DESCRIPTION

Internal Speaker for
monitoring regenerated
CW and CW I.D

AFSK to Xmtr

AFSK Level Control
to Transmitter To Xmtr Key

Jack for C W
AFSK Transmit
Shift Selector

Ground Center
RTTY feeback Conductor for
control Transmit mode

Used in Baudot Parallel
for printers ASCII Port

2

Input
Power Socket 20/60 ma

Current Loop Port
Rcvr Audio or RS 232 Drive port
Input

TTL Level
External Speaker TTY Output
or Tape Input

Input for Key, Keyer,
or CW Keyboard

Use for Ground Ext. Scope

Tuning Outputs

Hook Up Instructions

(Rear Panel Connectors)

POWER

The MBA-RC requires a 13 ±3 VDC, well filtered power source
capable of supplying 1.2 amperes. The power connector is a

2.1 mm center pin coaxial type, the center pin is positive.

AUDIO

The audio IN-OUT jacks are 3.5 mm phone jacks and are paralleled
in the MBA-RC. The IN (input) jack is used to provide receiver
audio, CW or RTTY signals to the MBA-RC. Receiver audio can
be taken from the headphone jack or by tapping the speaker leads.
The audio OUT (output) jack is provided for an external speaker
or tape recorder.

KEY

3

The key input is a contact closure input for CW. A standard two
conductor ¼" plug is used. It may be connected to a hand key,
keyer POSITIVE keyed output, or keyboard output.

SCOPE OUT

The mark and space filters output are provided at these
connectors for tuning RTTY signals with the aid of an X-Y scope.

KEYED + AND -

The + and - keyed outputs are for CW keying of the transmitter.
The + keyed output is for use with transistor and cathode keying,
and the - output is for use with transmitters using blocked
grid keying.

DATA OUT

The Data Out jack is a TTL level teletype output and is active
only in teletype modes. The output level is low during MARK.

CURRENT LOOP

The current loop input and output may be used with 20 or 60 mA
teletype loops. Warning! The Teletype Current Loop Supply must
be externally limited to 60 mA maximum. Optical couplers
isolate the current loop input and output from the rest of the
MBA-RC electronics.

PARALLEL ASCII

The parallel ASCII input and output are provided on the right and
left sides of the 26 pin parallel connector. The parallel output
is Centronics compatible parallel and may be used with
Centronics, Epson and other parallel input ASCII printers. The
parallel input is seven bit ASCII, TTL Level, high true with a
low true strobe.

4

TRANSMIT/RECEIVE

The XMIT/RCV input requires a contact closure during transmit
to select the front panel transmit mode switches. This input
provides automatic switching of the input and output modes when
switching between transmit and receive if activated with an
auxilliary set of contacts on your transmitter.

TONE OUT

The Tone Out connector is the AFSK tone output and is 2125 Hz
Mark and 2295 Hz space on 170 Hz Shift, and 2125 Hz Mark and
2975 Hz Space on 850 Hz shift. This input may be connected to
the microphone or phone patch input of your transmitter for
RTTY operation. The AFSK Output Level of the AFSK tone is set
with a screwdriver at the adjustment pot.

TRANSMISSION OF BAUDOT-RTTY

WARNING.....WARNING.....WARNING.....WARNING.....WARNING

During RTTY transmissions your transmitter operates in a key­down mode. Most amateur transmitters can be damaged by con­tinous operation at the1r normal CW input power levels. It
will be necessary to reduce input power when using AFSK tele­type to about 40% of the normal CW input power. Consult the
Owner's Manual for the transmitter you are using.

AFSK SHIFT

The AFSK Shift push switch selects 170 Hz (In position) or
850 Hz (Out position) AFSK output.

5

SPEAKER LEVEL

Spk Lvl set adjustment pot for CW monitor tone level.

DOWNSHIFT ON SPACE

The two Down Shift on Space switches are used for Baudot tele­type reception and transmission. With the Down Shift on Space­RCVR switch OUT, an automatic downshift is generated when
a space character is received for reducing the amount of
garbled print. To reduce transmission errors, it is recom­mended that you operate with the Down Shift on Space-Xmit switch
in the IN position.

PRINTER LOCK UP

Printer Lock Up On Receive push button has two functions. When
the MBA-RC is used with a current loop input, the switch in the
OUT position prevents input to the MBA from the keyboard when
in the receive mode. This allows local loop operation without
'feedback' through the input and output of the MBA-RC.

PRINTER LOCK UP ON XMIT

The Printer Lock Up On Xmit push switch, when in the OUT po­sition, prevents operation of the printer by the MBA-RC when
transmitting. These two lock up functions are particularly
useful during mode conversion operation, e.g., Baudot transmit
and receive while using an ASCII teletype machine.

REAR PANEL CONNECTOR GUIDE

REAR

PANEL

CONNECTIONS

6

2.1 mm COAXIAL

3.5 mm

RCA

¼” STANDARD

2 CONDUCTOR

CURRENT LOOP

3 PIN CONNECTOR

PARALLEL ASCII

IN/OUT PLUG

POWER PLUG X
AUDIO IN X
AUDIO OUT X
SCOPE MRK SPACE X
KEY X
DATA OUT X
CURRENT LOOP X
Parallel ASCII X
XMIT/RCV X

- KEYED X
+ KEYED X
TONE OUT X

WARNING:

All interconnecting cables should be shielded and the equipment
properly grounded, use one of the two screws on the rear panel
(see Rear Panel Description, page 2 ). Extra care in this re­gard will payoff in proper performance of your equipment. If
you have questions about grounding procedures please refer to the
Amateur Radio Handbook published by ARRL.

REAR PANEL CONNECTIONS

BLOCK DIAGRAM

7

FRONT PANEL CONTROLS

The front panel controls may seem somewhat confusing because of
the tremendous flexibility of the MBA-RC. Therefore it is ex­tremely important that you read and understand this section
thoroughly.

Immediately beneath the display there are two switching areas
marked Input on the left and Output on the right. This needs
explanation since the two switches under each refer to transmit
and receive. The Input
refers to outputs from the MBA-RC.

There are basically three ways you can transmit using the
MBA-RC, CW using a hand key or paddle via a keyer, Baudot or
ASCII TTY using a keyboard, or TTY machine. Input is usually
from two sources:

1. The station you hear via your receiver.

2. Your key/keyer, keyboard, TTY machine or terminal.
For input from the receiver, the slide switch will be set on the
Receive side for the mode and speed being received. For input
from your key/keyer, keyboard, etc. you will set the input
transmit switch to the proper speed and mode desired.

refers to inputs to the MBA-RC and Output

8

Under the Output area there are again two switches, one for
transmit and one for receive. In this case you will be setting
the switches to do two things:

1. Set the MBA-RC to transmit a particular mode.

2. Set the receive switch at the Output mode and speed

desired when receiving the other station. This is the
switch used to select the proper output for generating
printer hard copy of received signals.

If this is still confusing, some examples of the Input/Output
transmit and receive switch settings are given for various modes
of operation. These illustrations cover settings used in the
Input and Output controls and controls on the rear panel.

ILLUSTRATION 1

CONDITION:

Your Station: Working Morse Code-using 32 character display
Other Station: Working Baudot, 60 WPM

You are input- You are receiving The MBA-RC is out- This setting
ting Morse to Baudot at 60WPM putting Baudot at is for use to
MBA-RC with key, 0n 32 character 60WPM to your Xmtr. drive your own
keyer, or CW display. current loop
keyboard. printer.

NOTE: SEE PAGE 21 AND

PROGRAM “ DE “
(your call letters)
INTO THE I.D. BUFFER.

9

Place transmit output
switch in Morse and
push ID button at end
of transmission.

In On On

With your receiver
tune for Max. Norm (Tune
closure with no Receiver into
flickering. LSB position)

ILLUSTRATION 1 (con’t.)

Adjust for To TX MIC
suitable level Input
into TX MIC
Input

10

•

RX

TX

–

To 12 V Pwr.
Supply
@ 1.2 A Current Loop

Output to
To RX Printer
Speaker out

To Remote Pins 5 4 3 1
Spkr. •

In –

Adjust for Keyboard and
reasonable CW Selection Magnets
monitor level in Series
during I.D. Mode

Input from
Key, Keyer, or
CW Keyboard