The new model MBA-RC (Morse, Baudot, ASCII
Reader/Code Converter) represents another significant
breakthrough in data communications equipment from
Advanced Electronic Applications, Inc. The MBA-RC is
actually several sophisticated devices all wrapped up
in one package.
The unit performs as a full function decoder and
display unit for Morse, Baudot (teletype) and ASCII
(teletype/computer) coded signals. The MBA-RC
operates directly from the audio output of any stable
communications receiver, with no other accessories
necessary except a 12 VDC source. The MBA-RC also
encompasses a feature-packed Morse, Baudot and
ASCII encoder and code converter. The unit will perform serial to parallel and parallel to serial code con-
versions as well as cross-mode conversions. All the
necessary analog processing and tone generation for
two way contacts in any of the MBA codes is included
in the standard unit.
Two powerful AEA microcomputers, 43 integrated
circuits, and all the associated circuitry comprising the
MBA-RC are contained within one compact and handsomely designed package. The package takes up little
extra operating space and lends itself nicely to portable
two-way RTTY operation from a 12 VDC source.
Morse, Baudot and ASCII Reader Features
The MBA-RC incorporates very advanced analog
signal processing circuitry for allbwing maximum
readability of weak or interfered with signals. The MBARC is compatible with all the standard HF, VHF and UHF
Amateur RTTY modes (plus non-encrypted news or
weather broadcasts). Separate receive filters are
positioned ahead of and behind a special signal limiting
circuit (pre and post limiting filters).
A four-pole two stage active CW filter can be frontpanel tuned for any audio frequency between 300 Hz
and 2KHz. RTTY (Baudot or ASCII) signals are processed by separate Mark and Space filters for maximum
noise and interfering signal rejection. The RTTY filters
are tuned for a fixed 170 Hz shift (2125 Hz Mark/2295
Hz Space) or a front panel selected variable shift from
100 to 1000 Hz (2125 Hz Mark/2225-3125 Hz Space). A
normal/reverse switch is provided for receiving RTTY
on the opposite sideband (upper). Separate Mark and
Space tuning LED's are provided on the front panel. For
operators having an oscilloscope handy, separate Mark
and Space signal outputs are available for conventional
scope tuning.
Sufficient amplification is provided in the MBA-RC input circuitry to ensure good copy from low audio input
signal levels. The MBA-RC also accepts TTL input
voltage levels, contact closures (such as Morse hand
key), a 60 mA or 20 mA keyboard loop, serial (ASCII or
Baudot), or parallel ASCII inputs.
The MBA-RC comes with a 32 character alphanumeric vacuum fluorescent display. Each character is
0.29 inches high. No external CRT or TV is required.
There are no noisy mechanical parts to wear out or
break down during normal monitoring. However,
Printer output is available for obtaining hard copy with
an external printer when it is desired.
The MBA-RC has most of the features of the AEA
model MBA-RO (reader only) including the exclusive
AEA instant Morse automatic speed tracking capability
from 3 to 80 + WPM. The speed of the received Morse
signal is computed and can be displayed at the far right
of the display at the completion of each word.
Baudot RTTY input speeds of 60, 67, 75 and 100
WPM are all accepted by the MBA-RC reader. ASCII
RTTY input speed of 110 Baud is also copied by the
MBA-RC.
Outputs from the MBA-RC can be used to drive
popular serial Baudot Teletype printers such as models
15, 19, 28, and 32 or ASCII teletype machines such as
the models 33 and 35. In addition, the MBA-RC will
drive most of the popular parallel ASCII printers such
as Epson and Centronics.
MBA-RC Encoder Features
Any standard Baudot or ASCII parallel keyboard, a
current loop, even two-tone AFSK can be used to drive
the MBA-RC. Regardless of the type of input, any of the
three output codes can be generated at any of the
MBA-RC available output speeds. Morse code input
from a hand key, bug, keyer or memory keyer (even a
Morse keyboard), can be instantly converted to Baudot
or ASCII two-tone RTTY output for driving a SSB
transmitter at the audio input jack. It will also drive FSK
transmitters from a transistor keyed output port. When
used with a Morse memory keyer, high speed RTTY
transmissions can be made without the need of a
keyboard.
Any Morse, Baudot or ASCII input code can be converted to any of the three ouput (Morse, Baudot or
ASCII) codes. Also, any available specified MBA-RC input speed can be converted to any available specified
MBA-RC output speed. A 1000 character dynamic
storage buffer is particularly useful for code conversions from high speed inputs to low speed outputs
(such as 110 Baud ASCII to 20 WPM Morse). A buffer
limit LED will indicate when you are about to type too
much into the buffer -For example, about five minutes
of continuous 110 Baud ASCII can be fed into the MBARC for conversion to 60 WPM Baudot output before the
buffer limit LED comes on.
The MBA-RC will transmit 1 to 99 WPM Morse code.
The output speed for Morse can be set from an ASCII or
Baudot keyboard by typing $NN, such as $25 for 25
WPM. A built-in CW sidetone monitor including a
speaker is also standard equipment in the MBA-RC.
A built-in AFSK tone generator is also featured with
170 Hz or 850 Hz shift selected by a rear panel switch.
Either of the shifts can be internally adjusted to any
other shift between 100 and 1000 Hz. The AFSK
generator uses a clean, stable function generator (not a
555 timer) that is factory tuned to 2125/2295 and
2125/2975 Hz.
An automatic CR/LF (carriage return/line feed) is
generated in receive or transmit mode following the
first word space after 64 characters on a line or after
72 characters if no space occurs. This feature is commonly referred to as word wrap-around. The feature is
easily defeated with a front panel switch for such things
as receiving RTTY pictures.
An anti-space (mark-hold) mode is automatically
enabled after about a second of continuous space
tone. This mode eliminates the undesired effect of having a printer running' 'open-Ioop' , .Another convenient
feature is automatic down shift on space for Baudot
reception or transmission. Otherwise known as USOS
(unshift on space), it is independently selectable for
transmit and/or receive on the rear panel.
An automatic station identification memory message
is offered in the standard MBA-RC which can be activated by a front panel switch. The output generates
less than a 50 Hz tone shift as well as a simultaneous
CW keyed output. It can also be used for standard
BAUDOT or ASCII message transmission.
An external contact closure applied to a rear panel
jack will automatically change the selected input and
output modes from receive to transmit.
General MBA Features
The MBA-RC is packaged in an attractive metal
enclosure with a handsome front panel that is humanly
engineered for easy operation. Operating status indications are provided for Morse speed, Mark and Space
tune, and transmit and receive active modes in operation.
A bullt-in high and low voltage inverter power supply
allows operation from an external 12 volt power source.
The unit is diode protected against inadvertent reverse
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