1274.4
 
According to MFJ, the following is the correct Calibration
Routine for the MFJ1274 and 1270B TNC's. I received this in the mail
from MFJ....I added my personal comments (...) to aid you in this proceedure.
73...Jim : NJ3T
 
0. Connect counter to u21 pin 20, set c47 to 4.915205 mhz
1. Put jumpers on j4(disables tx watchdog timer) and j7(enables analog loopback
   mode)
2. Switch [5] & 6 on, where [ ] is for terminal speed (Here they are asking for
   a terminal baud rate of 9600 and a radio baud rate of 300. I did this
   routine at a radio baud rate of 1200. After setting it for 300, i did not
   notice any drastic changes in my frequency measurments)
3. Power ON
4. cmd:cal (In the command mode, type "CAL")
5. type K : DCD and PTT (lights) come on
6. Connect counter to j9, next to c40
  (     J9                                 ^Rear of TNC )
  (   o o o<--counter probe to this pin                  )
  (   o o o                               \/Front of TNC )
 
7. Set r78 to 1200 hz with HF/VHF switch out
8. Set r77 to 2200 hz
9. Push HF/VHF switch in
10. Set r106 to 1600 hz
11. Set r105 to 1800 hz
12. type D
13. Connect scope to j10 next to q14
14. Adjust r79 for square-wave : top and bottom equal length
    (Signal on scope should show a 50% duty cycle square wave, uniform in width
    ....pulse duration of appx 2.4ms)
STOP HERE FOR 1270B
15. Set r212 for LED under "u" of "TUNE" (10th LED segment from the left.)
16. HF/VHF switch out, check for LED close to "E",(10th LED segment from the
    right) if not go to step 14.
 
Dated "7/3/90"
I found that calset should be "32"