MFJ-1270C/1274C MANUAL TABLE OF CONTENTS
vii
Symptom: The MFJ-TNC signs on OK but won't accept
commands. .....................................................................................223
Symptom: The MFJ-TNC appears to have "locked-up" i.e. not
responding to any commands.........................................................224
PACKET RADIO PROTOCOL...................................................................225
Explanation of Protocol .................................................................225
Physical Layer .................................................................225
Data Link Layer...............................................................226
HDLC Frames .................................................................226
AX.25 Level Two ..........................................................................227
Channel Use and Timing Functions .............................................................230
Channel Flow Control ..................................................................................232
RADIO HOOKUP .......................................................................................233
MODEM CALIBRATION ..........................................................................234
Modulator and Demodulator Frequency Calibration .....................234
Method I ..........................................................................234
HF Modem ........................................................234
VHF Modem .....................................................235
METHOD II ....................................................................235
Set Modulator Tones Using Built-in Calibration
Software...........................................................................236
Demodulator Center Frequency Alignment .....................237
Tuning Indicator Alignment ............................................238
MFJ-TNC Adjustment Location Map..........................................239
AUDIO OUTPUT CALIBRATION..............................................241
Audio Output Level Adjustment Procedure...................................241
HF RADIO ALIGNMENT ..........................................................................243
First method: NOISE AVERAGE FREQUENCY.........................243
Second method: FILTER SKIRT AVERAGE FREQUENCY ......243
MFJ-TNC 2400 PACKET OPERATION..................................................245
2400 Packet Operation Setup.........................................................245
B. Receive Audio Setting ...............................................245
C. Transmit Audio Setting..............................................246
JUMPER FUNCTIONS AND LOCATIONS..............................................247
COMMAND SUMMARY...........................................................................250
