MFJ MFJ-1225 User Manual

MFJ-1225 RTTY/CW COMPUTER INTERFACE

Thank you for purchasing the MFJ-1225 Interface. The MFJ-1225 will allow
you to receive RTTY and CW when used with your receiver and computer. The
MFJ-1225 converts the CW or AFSK tones from your rec ei v e r i n t o c o m p ut e r
compatible TTL level signals. The computer then translates these signals into the
represented alpha-numeric characters and displays them on the screen.

NOTE: The interpretation of the TTL signals requires a specialized HAM
program which is not provided with the interface. This allows you to select a
program which is compatible with your computer and which has the features you
want.

When unpacking make sure that all of these items are included: 1- in terf ac e, 1 ­five pin plug, 1-eight pin plug, 1-RCA to RCA cable, 1-owner's manual. NOTE:
12 VDC AC adapter is optional.

FRONT PANEL

The front panel controls and indicators consist of five push button switches and three
LEDs. From left to right, they are as follows:

ON/OFF - This switch controls the power to the interface. POWER
LED - This indicator is lit when the power is on.

PHASE LOCK LED - This indicator is used with DATA indicator aid in tuning the
receiver. It indicates when the interface locked onto a RTTY signal. It also flashes in time
with the M o r s e C o d e t o ne for CW reception.

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DATA LED - This indicator is used with the PHASE LOCK indicator to aid in
tuning the receiver. It flashes on and off with the RTTY shift and also flashes with the
Morse Code tone for CW reception.

RTTY/CW - This switch selects either the RTTY or CW mode of operation. The nex t t wo
switches control the shift used for RTTY.

In this position, the Interface receives with a 850 Hz audio shift.
In this position, the Interface receives with a 170 Hz audio shift.
In this position, the Interface receives with a 425 Hz audio shift.
NORM/REV - This switch inverts the demodulated RTTY signal being sent to the

computer.

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BACK PANEL

The MFJ-1225 provides inputs and outputs to allow interfacing to nearly
any possible combination of computer and r e c e i v e r. T h e paragraphs below describe
their uses. Only a few of the available connections will be used for any given
application; however, the
availability of a variety of signals greatly enhances versatility of the interface.

The first connector is a five pin Kantronics compatible jack. Only two pins are used and
they are:

DEMOD - This pin produces a TTL signal which corresponds to the coming RTTY or
CW signal.

GROUND - This pin provides the ground connection between the inter face and the
computer.

Next is an eight-.pin general purpose connector which allows you to adap t the
interface to most any computer and software. From left to right, the p i ng a re a s
follows:

RTTY I NV - This pin produces an inverted TTL level version (a received RTTY signal).
CW INV - This pin provides an inverted TTL level version (a received CW signal).

GND - Thi s pin p ro vide s the g roun d con n e c tio n bet w e en t h e com put e r and th e
interface.

RTTY - This output is a TTL level version of a received RTTY signal.

CW - This output is a TTL level version of a received CW signal. The next pin is not used.
DEMOD - This pin provides a TTL level signal which corresponds to the incoming CW or

RTTY signal.
AUDIO IN - T he a u di o input jack should be connected to the external speaker jack or

headphone jack of your receiver with a shielded audio cable. The interface end of
the cable requires an RCA type plug.

SPEAKER O UT - The speaker output jack should be connected to a speaker using shielded audio
cable. The interface end of the cable requires an RCA type plug.

12 . VDC - The power jack requires 12 VDC from a 2.5mm subminiature plug with the tip
positive and the sleeve ground.

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