TNC2.8

     b. Find  some 4-40 or 6-32 threaded (preferably aluminum) spacers  and 
        cut off a 0.30" piece. Use this threaded spacer as the mounting nut 
        for the 7805 on the back side of the board with a short screw going 
        thru  the  tab on the top side of the board.  After you  slide  the 
        board  into  the cabinet,  use a second short screw to  "bond"  the 
        spacer to the cabinet
The  WB6RQN report on LM358=U8 problems in modem calibration is  similar 
to  that experienced by the TNC2 "beta" group.  The problem is that  the 
'358  is supposed to give a digital signal from the 2211 which  is  then 
counted  in software to set the frequency. But there was a tendency for
oscillations to occuras the signal went thru zero crossings,  leading to 
a bogey count. In addition to the 0.1 uf cap between pins 3 & 4 on U8, I 
also found that replacing U8 with a TI TLC272 low-power (and slow!!!) op 
amp which can be obtained at your local Radio Shack (part no.  276-1749, 
$2.19) solved all my problems.
CONTINUED IN FILE TNC2.14