MDMTEST1.EXE and MDMTEST2.EXE are simple programs written to help you
with tuning the RXB of your TCM3105 based modem. I found this voltage
to be critical for modem's performace and how -cd option of ax25.com
driver works.

Bad RXB causes the output of the TCM3105 to be asymetric.
Suppose you receive a FSK signal modulated with square wave
like: 010101010101010101... With proper RXB you get square wave
with 50% duty cycle out of pin 8 of TCM3105. With bad RXB
positive pulses are of different length then negative ones.

mdmtest1.exe takes modem's output and measures the lengths
of positive and negative pulses. Then it computes the deviation
from full bit periods (for 1200 bps the bit period is 1sek/1200 = 0.83 ms)
For synchronous transmition the pulse width should be a multiply
of bit period. The program displays the average deviation
from this rule. Ideally the deviation should be zero when a clean packet
signal is being received. See it yourself...

mdmtest2.exe does similar thing but it takes the period between
modem's output transitions of same polarity. This value is used
in improved algorithm for -cd option and it should in principle
be insensitive to small RXB variation. But again: see it yourself...