MFJ MFJ-1225 User manual

MFJ RTTY/CW
COMPUTER INTERFACE
MODEL MFJ-1225
OWNER'S MANUAL

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MFJ-1225 RTTY/CW COMPUTER INTERFACE
Thank you for purchasing the MFJ-1225 Interface. The MFJ-1225 will allow you to receive
TTY and CW when used with your receiver and computer. The MFJ-1225 converts the CW or
AFSK tones from your receiver into computer 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-interface, 1-five pin plug, 1-eight pin plug, 1- CA to CA 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.
POWE LED This indicator is lit when the power is on.
PHASE LOCK LED This indicator is used with DATA indicator to aid in tuning the receiver. It in-
dicates when the interface is locked onto a TTY signal. It also flashes in
time with the Morse Code tone for CW reception.
DATA LED This indicator is used with the PHASE LOCK indicator to aid in tuning the re-
ceiver. It flashes on and off with the TTY shift and also flashes with the
Morse Code tone for CW reception.
TTY/CW This switch selects either the TTY or CW mode of operation.
The next two switches control the shift used for TTY:
In this position the interface is set for a 850 Hz audio shift
In this position the interface is set for a 170 Hz audio shift
In this position the interface receives with a 425 Hz audio shift.
NO M/ EV This switch inverts the demodulated TTY 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 com-
bination of computer and receiver. The 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 TTY or CW
signal.
G OUND This pin provides the ground connection between the interface and the com-
puter.
Next is an eight-pin general purpose connector which allows you to adapt the interface to
most any computer and software. From left to right the pins are. as follows:
TTY INV This pin produces an inverted TTL level version (a received TTY signal).
CW INV This pin provides an inverted TTL level version (a received CW signal).
GND This pin provides the ground connection between the computer and the in-
terface.
TTY This output is a TTL level version of a received TTY 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 TTY signal.
AUDIO IN The audio input jack should be connected to the external speaker jack or
headphone jack of your receiver with a shielded audio cable. The interface
Cnd of the cable requires an CA type plug.
SPEAKE OUT The speaker output jack should be connected to a speaker using shielded
audio cable. The interface end of the cable requires an CA type plug.
12 VDC The power jack requires 12 VDC from a 2.5 mm subminiature plug with the
tip positive and the sleeve ground.

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INTERNAL CONTROLS
The MFJ-1225 has two internal controls, as described below:
INPUT LEVEL The input level pot is located in the rear, left corner. It is very important that
the input is set to the proper level for use with your rig. First tune the radio
until no signal is heard (static only) then set the volume slightly louder than
your normal listening level. Turn the input level pot to the point where the
static does not cause any flickering of the Phase Lock LED.
PHASE LOCK The phase lock pot is located in the front, right corner. The phase lock con-
trol is set at the factory and should not need to be changed unless extended
use causes frequency to drift.
CONNECTIONS
FO CW For reception of CW signals the following connections are necessary:
1) A 12 VDC power supply to the POWE jack of the interface.
2) A shielded audio cable from the external speaker jack of the receiver to the AUDIO in jack of
the interface.
3) If desired, a speaker may be connected to the SPEAKE OUT jack of the interface.
FO TTY/ASCII For reception of TTY or ASCII signals the following connections are needed:
1) A 12 VDC power supply to the POWE jack of the interface.
2) A shielded audio cable from the external speaker jack of the receiver to the AUDIO in jack of
the interface.
3) If desired, a speaker may be connected to the SPEAKE OUT jack of the interface.
OPERATION
In both TTY/ASCII and CW operation, the tuning of the receiver is the key to proper re-
ception'. Follow the guidelines below, but feel free to experiment. The optimum settings will vary
from one rig to the next.
FO TTY/ASCII - To receive TTY or ASCII set the interface to the TTY and 170 position and be-
gin tuning the receiver until a station is heard.
With the program set to 60 words per minute (WPM) operation, slowly tune the receiver so
that the TTY signal begins at a low pitch and slowly rises. Watch the PHASE LOCK and DATA
LEDs. When the receiver is properly tuned, the PHASE LOCK LED will light and remain lit, while the
DATA LED blinks in time to the tone shifts. Try the 425 and 850 positions also, to see which pro-
vides the clearest copy. If the signal appears to be received properly but the screen display is
garbled, try changing the reception speed or change the NO M/ EV switch.
FO CW - Connect the interface as described above. Load your HAM program and tune your re-
ceiver to a station. Set the interface to the CW position and the program to 'the CW mode. Tune

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the receiver until a Morse signal is heard. Starting with a low pitched tone, tune the receiver so
that the pitch slowly rises. When the receiver is tuned properly, the PHASE LOCK and DATA LEDs
should blink together in time with the CW tones. If the signal is very noisy, it will be necessary to
set the volume of the receiver to a lower level.
In both TTY/ASCII and CW operation, some signals may not be copyable. This may be be-
cause of high levels of noise, coding of the message, transmission in a foreign language or other
reasons.