MFJ MFJ-1270C, Системное руководство

Страница: 243 / 264

MFJ-1270C/1274C MANUAL APPENDIX B: CALIBRATION
Page 234
MODEM CALIBRATION
The MFJ TNC is factory calibrated to operate to within factory guidelines. If it
becomes necessary to re-calibrate the modem, then the following procedure is
provided.
Modulator and Demodulator Frequency Calibration
Here we present two (2) Modulator and Demodulator calibration methods.
Method I requires test equipment as noted, where Method II does not require test
equipment.
Method I
HF Modem
Test equipment needed: Frequency Counter and probe and oscilloscope with
probe.
1.
Install push-on jumpers on JMP 4 and JMP 7.
2.
Verify a push-on jumper is installed on JMP 8.
3.
In the following procedure all frequencies are to be set to /- 2 HZ.
4.
Place the frequency probe at JMP 9 pin 1. This is the top pin.
5.
Place the oscilloscope probe on top pin of JMP 10.
6.
Set dip switch #6 ON.
7. Set one of the dip switches 1 thru 5 to the Computer Baud Rate which
appiles to the baud rate being used on the computer.
8. Push
the VHF/HF switch to the HF position.
9.
Initiate the calibration mode by typing:
CALIBRATE <ENTER>
10. Now the modem must be keyed up. Do this by pressing the
K key.
11. Check the voltage on pin 9 of U16. Press the
SPACE BAR until this pin
indicates -5 VDC.
12. Adjust R106 to where the frequency counter indicates 2125 Hz +/- 2 Hz.
13. Press
the SPACE BAR until pin 9 of U16 ind5 VDC.
14. Adjust R105 to where the frequency counter indicates 2295 Hz,+/- 2 Hz.
15. Press
the
D
key.
16. Locate R212, which is near the front of the PC board by the tuning
indicator. Adjust R212 until the 10th led from the left is lit on the tuning
indicator. This enables proper signal tuning within the HF bands.
VHF Modem