MFJ MFJ-1224 User Manual

MFJ-1224 Instruction Manual

RTTY/CW Computer Interface

MFJ-1224 RTTY/CW COMPUTER INTERFACE

Thank you for purchasing the MFJ-1224 Interface. The MFJ-1224 will allow you to transmit and receive RTTY and CW when used with your transceiver. During reception, the MFJ-1224 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. In the Transmit Mode, the computer generates the TTL signals which are converted by the Interface into AFSK tones for RTTY or into CW keying for CW transmission.

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) EIGHT PIN MIC PLUG, (1) RCA CABLE, (1) FIVE PIN PLUG, (1)MIC CABLE WITH FIVE PIN PLUG ATTACHED, and (1) OWNERS MANUAL. THE 12VDC AC ADAPTER IS OPTIONAL.

FRONT PANEL

The front panel controls and indicators consist of five push button switches and four L.E.D.'s. From left to right, they are as follows;

ON/OFF This switch controls the power to the interface.

POWER L.E.D. This indicator is lit when the power in on.

PHASE LOCK L.E.D. This indicator is used with the DATA indicator to aid in tuning the receiver. It indicates when the interface is locked onto an RTTY signal. It flashes with the Morse Code tone for CW reception.

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

CW Transmit L.E.D. This indicator is activated by the CW keying circuit. It flashes during CW transmission.

MFJ-1224 Instruction Manual

RTTY/CW Computer Interface

RTTT/CW This switch selects either the RTTY or CW mode of operation.

Shift The next two switches control the shift for RTTY.

In this position the interface is set for a 850Hz audio shift.

In this position the interface is set for a 170Hz audio shift.

In this position the interface is set for a 425Hz shift and 170Hz sending shift

In this position the interface is set for a 425Hz shift and 850hz shift.

NORMAL/REVERSE This switch inverts the demodulated RTTY signal being sent to the computer.

BACK PANEL

The MFJ-1224 provides inputs and outputs to allow interfacing to nearly any possible combination of computer and transceiver. The back paragraphs below describe their uses. Only a few of the available connections will be used for an given application; however, the availability of a variety of signals greatly enhances the versatility of the interface.

LOOP OUT The loop-out jack provides the ground return to drive loop type teletypes. The user must connect the negative supply voltage to the sleeve. The center pin is a

MFJ-1224 Instruction Manual

RTTY/CW Computer Interface

continuation of the negative supply. The loop out merely acts as a spst switch switching the loop current on and off.

DIRECT KEYING This output keys rigs requiring direct keying (most rigs with solid state finals).

GRID BLOCK KEYING This output keys rigs requiring grid block keying (most rigs with tube finals).

KEY IN This input jack allows you to externally key the transmitter with your own electronic keyer or keyboard.

DEMOD OUT The demodulated output provides a TTL level signal which corresponds to the incoming RTTY space. It is also low for CW tone.

The next connector is a five pin jack, labeled K-connector because it is specifically designed for use with KANTRONILCS software. From left to right the pins are as follows:

DEMOD This pin produces the same output as the DEMOD OUT jack.

GROUND This pin provides the ground connections between the interface and the computer.

CW KEY This input pin allows the computer to key the transmitter through the interface. A low on this pin causes the interface to key the transmitter.

RTTY This input controls the AFSK for RTTY transmission. It works in conjunction with CW ID signals and to operate the push-to-talk switch. This will be covered in detail later.

CW ID This line controls the audio tone for CW identification. It works in conjunction with the RTTY line to produced RTTY and CW ID signals and operate the push-to talk switch. This will be covered in detail later.

MFJ-1224 Instruction Manual

RTTY/CW Computer Interface

Next is a eight pin general purpose connector which allows you to adapt the interface to almost any computer and software. An internal DIP switch allows the inputs and outputs to be inverted if necessary to correspond to the requirements of your computer. From left to right, the pins are as follows:

RTTY DEMOD This output is a TTL version of a received RTTY signal.

GROUND This pin provides the ground connection between the interface and the computer.

CW ID This input pin controls the shift for CW ID transmission.

RTTY This input pin controls the mark and space shift for RTTY transmission.

PTT This input controls the push-to-talk switch of the transmitter.

CW KEY This input controls the transmitter keying circuit.

+5VDC This input provides a 5 volt supply for external circuitry such as an RS-232 converter.

Next is a five-pin jack which is used for the microphone connection. From left to right, the pins are as follows:

PTT OUT This pin is connected to the high side if the push-to-talk line. It is shorted to ground to key the microphone.

PTT GROUND This pin is connected to the ground side of the push-to -talk line.

AFSK SHIELD This pin is connected to the ground for shield side of the AFSK line

AFSK OUT This line carries the audio signal for AFSK RTTY to the microphone input.

FSK OUT This line provides FSK signal for keying FSK rigs.

MFJ-1224 Instruction Manual

RTTY/CW Computer Interface

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 end of the cable requires a RCA type plug.

SPEAKER OUT The speaker output jack may be connected to a speaker using shielded audio cable. The interface end of the cable requires a RCA type plug.

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

PRELIMINARY CONNECTIONS

Input and output signals must be TTL level (+5VDC and ground). Inputs are RTTY and CW KEY(RTTY and CW on general purpose connector). There is also a separate CW ID input for identifying in MORSE while operating RTTY. Outputs are DEMOD (RTTY DEMOD and CW DEMOD on the GINERAL PURPOSE CONNECTOR) and DIRECT and GRID BLOCK. Connections depend on the type of computer and transceiver used. Either the GENERAL CONNECTOR or the K-CONNECTOR will be connected to the computer.

CONNECTIONS

FOR CW For transmission and reception of CW, the following connections are necessary.

1.) A 12VDC power supply to the POWER jack of the interface.

2.) A shielded audio cable from the external speaker jack of the transceiver to the AUDIO IN jack of the interface.

3.) If desired, a speaker may be connected to the SPEAKER OUT jack of interface.

4.) If the interface is to be used to key the transmitter by hand, the key should be connected to the KEY IN jack.

5.) The control cable from the computer to the interface.

6.) A cable from one of the KEY OUT jacks of the interface to the KEY IN jack of the transceiver. If you are not sure whether your transceiver requires GRID BLOCK or DIRECT KEYING, try one and then the other to see which one works. No damage will be done if the wrong one is selected.

MFJ-1224 Instruction Manual

RTTY/CW Computer Interface

FOR RTTY/ASCII For transmission and reception of RTTY or ASCII signals the following connections are needed:

1.) A 12VDC power supply to the POWER jack of the interface.

2.) A shielded audio cable from the external speaker jack of the transceiver to the AUDIO IN jack of the interface.

3.) If desired, a speaker may be connected to the SPEAKER OUT jack of the interface.

4.) The microphone/PTT cable to the transmitter. This cable is supplied with the proper push on the connector on one end and with the other end unwired. This allows the cable to be connected properly for various types of transmitters. For transmitters that have three wire microphone connectors; only three of the microphone cables are needed. AFSK shield should be connected to ground ,PTT should be connected to PTT OUT, and AFSK should be connected to ground at the AUDIO INPUT. The FSK OUT is not connected when used for AFSK operation.

Consult the owner's manual for your transceiver to determine the proper connection of the MICROPHONE JACK. The white wire is the audio line, the red wire is the PTT line, the black wire is the PTT ground line, the bare (shield) wire is the audio ground and the green wire is the DSK line.

5.) The control cable from the computer to the interface.

6.) If the interface is to drive a TTY current loop. the TTY should be LOOP OUT pin is usually connected to the negative side of your selector magnets.

INTERNAL CONTROLS

Caution: Improper adjustments of the internal controls will prevent the interface from functioning.

The MFJ-1224 has several internal controls and adjustments, as shown in the diagram and described below. The layout is shown in FIGURE 4.

AUDIO OUT GAIN This controls the level of the audio for AFSK output. It is preset at the factory to a reasonable level for most transmitters. Some adjustments may be required if your transmitter requires a higher or lower setting. The best results usually occur with high level from the interface and a low mic gain setting on the transmitter.

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