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MFJ-1278B MULTI-MODE APPENDIX B MODEM CALIBRATION
8. Adjust R106 carefully until both the "CON" and "STA" LEDs on the front panel of the
TNC are lit. One of the leds may filcker slightly. This is normal.
9. Type a "Q". This exits the MFJ-1278B from calibrate mode to command mode.
10. Type CALSET n <CR>". Where n is a number determined by:
n = INT [ 525000 / F(high) ] + 1
11. Command the MFJ-1278B into calibrate mode by typing "CAL <CR>".
12. Command the MFJ-1278B to key the modem by typing "K".
13. Select the high tone by pressing the space bar until a voltmeter connected to U16, pin 9
reads + 5 volts.
14. Adjust R105 carefully until both the "CON" and "STA" LEDs on the front panel of the
MFJ-1278B are lit. One of the leds may flicker slightly. This is normal.
15. Type a "Q". This exits the MFJ-1278B from calibrate mode to command mode.
This completes the modulator tone alignment using the built in calibration facility. If you had
any problems with this section, then DO NOT go beyond this point. If you do the calibration
will be inaccurate. However, if all went well, then you may proceed.
Now that the modulator tones have been properly centered over the intended modem center
frequency (Fc), now the demodulator center frequency will be aligned.
Demodulator Center Frequency Alignment
1. Place push on jumpers at JMP 4 and JMP 7, if they are not already in place.
2. Remove jumper at JMP 9 pins 1 and 2. Place it at pins 2 and 3.
3. Remove the the jumpers at pins 1 and 2 and pins 3 and 4 of JMP 16. Replace the
jumpers at JMP 16 at pins 1 and 3, and pins 2 and 4. When finished the two jumpers at
JMP 16 should be positioned from side-to-side, with the leds on the MFJ-1278 facing
you.
4. Set the baud rate for use by RXCAL to 300 baud by typing "CALSET 32 <CR>". This
w
ill cause the modulator to send a square wave FSK signal when RXCAL is invoked.