User guide

MS-DMT Guide v1.04
Released 05-30-2014
87
“ERROR” - The Doppler Spread or Frequency Error has a display range of -999.99 to 999.99hz
where the modem must properly decode an incoming signal that is off frequency by as much as
+/- 75Hz (including transmitter/receiver frequency variations and doppler spread). The modems
RF frequency error correction in this software exceeds that requirement of the standard. The
sample clock error does not enter into this error correction. The frequency error display during
the hunting for a signal will periodically jump about with significant numbers, however when a
legitimate signal is detected the display will be constantly changing and displaying lower and
lower values as the preamble is being decoded and frequency error correction is being applied
until the completion of that task and then it will lock onto displaying the last frequency error
value until DCD is reset.
NOTE: There no need to touch up the RX frequency to deal with the error unless the error exceeds 75Hz
and DCD is being lost and then is must be done between rather than during transmissions.
NOTE: Any tuning of frequency must be done prior to MS110A transmissions. Do not try to tune in
MS110A as you would RTTY and other modes. You must be setup on the correct frequency at MS110A
transmit start. When a station is transmitting MS110A and you touch up your RX frequency during the
message being sent you will cause the software to work harder and you will likely loose DCD.
Incoming Message Window
Any received message is displayed in the upper window of the Receive panel in the “Incoming
Message Window”. The selection of “Display on EOM” determines if received messages are
displayed continuously or one at a time and automatically cleared on the next message EOM
received.
The RX message buffer has been set to the maximum of 2GB of system and virtual memory. This
may present a problem for some Vista users if the buffer is allowed to get to full before hitting
"Clear" based on some of the things I have read on issues with CEdit controls and Vista. Should
the message buffer ever hit the limit a message box will display an error message.
Check Boxes
“Display on EOM” - When "Display on EOM" is checked, only the last message received that will
be displayed, and done so all at one time on receipt of the End of Message (EOM) indicator.
When "Display on EOM" is not checked, each character is displayed as received and scrolls
smoothly line by during reception of the entire message. Even though the scroll bars are