MFJ MFJ-44X User Manual
MFJ-44X |
Scope Adapter |
MFJ-44X RTTY
Cross-Pattern Tuning Scope Adapter
Thank you for purchasing the new MFJ-44X RTTY Cross-Pattern Tuning Scope Adapter. The MFJ-44X can be used to filter the audio input of a Terminal Node Controller, Terminal Unit, or any equipment that decodes mark and space frequencies (2125 and 2295 Hz). The MFJ-44X also provides the user with separate Mark and Space outputs that can be fed into a monitor scope or a regular oscilloscope. When viewed on a scope the output is an elliptical cross-hair display which provides a accurate means of tuning various amateur radio signals. The MFJ44X will tune ASCII, RTTY, AMTOR, and PACTOR. The scope display can give the user useful information about the incoming signal, such as:
•Is the input Mark frequency high or low,
•Is the input Space frequency high or low,
•What is the actual frequency shift of the incoming signal?
Installation
JIM: Should we provide an interconnections diagram? It would be easier to follow
We will now cover installation of the MFJ-44X to a MFJ-1278 and scope. Installation with other demodulators will be virtually identical. Please follow the installation procedure closely.
1.Set the POWER switch to the OFF position. Connect an optional MFJ-1312B or compatible 12 to 16 VDC source to the MFJ-44X. The MFJ-1312B is available from MFJ. The power jack uses a 2.1mm coaxial connector with center conductor positive and sleeve ground. Incorrect power supply polarity can result in damage to the unit.
2.Connect the AUDIO IN jack, J2 of the MFJ-44X, to either the headphones output or an EXT speaker output of your receiver. A 3.5mm stereo (or mono) plug should be used with the TIP signal and the SLEEVE ground. The RING portion of a stereo plug is not used.
3.Connect the AUDIO OUT jack, J1 of the MFJ-44X, to the audio input of the MFJ-1278. A 3.5mm stereo (or mono) plug should be used with the TIP signal and the SLEEVE ground. The RING portion of a stereo plug is not used.
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MFJ-44X |
Scope Adapter |
4.Connect the output of the MARK and SPACE filters, J4 and J5, to your scope. The MARK and SPACE outputs are RCA phono jacks with the center conductor signal and the shield ground. The inputs on monitor scopes are usually RCA phono while oscilloscope inputs are BNC. Use a shielded RCA cable for your monitor scope or make a cable for your oscilloscope with the center pin signal and the shield ground.
Connect the MARK portion to the horizontal (X on oscilloscopes) input, and the SPACE to the vertical (Y on oscilloscopes) input.
5.Verify that all connections are correct. If you made or bought pre-made cables they should be checked for continuity and for shorts (from the shield to the conductors).
6.(For Oscilloscopes) Place the TIME/DIV knob into the XY position.
This completes the connection of the MFJ-44X to the MFJ-1278. You are now ready to align the MFJ-44X to your monitor scope.
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MFJ-44X |
Scope Adapter |
MFJ-44X to Monitor Scope Alignment
In this section we will align the MFJ-44X to your monitor scope. Please follow this procedure carefully.
NOTE: Before performing the MFJ-44X to scope adapter alignment it is a important that your demodulator is calibrated. Refer to your unit's instructions or refer to the following for calibrating a MFJ-1278/1278B.
Jim: you should probably divide the 1278 calibration and the 44 alignment. Also put the directions together and in order for each unit
MFJ-1278 calibration:
1.Apply power to your monitor scope and turn the unit "ON". You may want to turn the trace INTENSITY to minimum.
2.Place a push-on jumper at JMP4 in the MFJ-1278.
3.Short pins 1 and 4 of Radio Port 1 in the MFJ-1278.
4.Ensure that the POWER switch SW1 on the MFJ-1278 is set to OFF.
5.Connect the computer and apply power to the MFJ-1278.
6.Set the POWER switch on the computer to the ON position.
7.Load and execute the computer terminal program
8.Set the POWER switch SW1 to ON, and sign-on the MFJ-1278 to the computer.
9.Set the MFJ-1278 to the HF RTTY mode by typing:
MODE HB |
<ENTER> |
10. Set the MFJ-1278 into Calibration mode by typing:
CALIBRATE |
<ENTER> |
CONVERS |
<ENTER> or K |
11.Set the AUDIO INPUT LEVEL control R11 on the MFJ-44X to the midrange position.
12.Remove the top cover from the MFJ-44X.
13.Check the voltage on pin 9 of U16. If the voltage is -5 Vdc, then set R7 on the MFJ-44X, so the elliptical shaped trace on the scope is horizontal. Try to get this trace as horizontal as possible.
14.Adjust the HORIZONTAL and VERTICAL gain controls on your scope, to obtain the best elliptical shape possible.
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