User guide

MS-DMT Guide v1.04
Released 05-30-2014
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into the lower “Outgoing Message Window”. Then click “Send” to start the test and do nothing
else on the computer during the test. The message will take 1 minute and 10 seconds to
complete if uninterrupted.
Review the loop back message on the RX instance of the software and verify that you displayed
the message 100% correct. If 100%, your system (aside from possible sample clock error and
drift when not using the sound device in loopback) has passed the basic test.
You can repeat this test at all data rates using SHORT interleave, however 4800bps has more
potential to detect issue’s as it’s the least robust. The message will take 2x plus for each lower
data rate starting at 2400bps SHORT at 2 minutes and 22 seconds and 2 minutes 27 seconds for
2400bps LONG. The interleaving adds additional time beyond just the data rate change. If the
32kb test message does not pass at any data rate below 4800bps then your system has real
issues requiring mitigation.
RADIO RECEIVER SETTINGS
An MS110A waveform occupies an audio bassband of 300-3300Hz where STANAG 4203 (refer to
Appendix I herein) specifies the IF filtering and properties of the radio which receives the audio
signal (nominal 3 kHz bandwidth) from the modem and modulates it onto a carrier along with
radio performance specifications that are also detailed in MIL-STD-188-141C.
Per S4203, the base-band frequency response of the transmitter and of the receiver (IF filtering)
over the range 300Hz to 3050Hz (2.75kHz) shall be within, variations in attenuation are at most
+/-2 dB of the response at 1000Hz for manpack equipment and within ±1.5dB for all other
equipment and the group delay time over 80% of the passband must not vary by more than
0.5ms. In addition the time constant of the automatic gain control (AGC) circuit must be more
than 10ms on desensitization and less than 25ms on resensitization. The frequency accuracy of
the transmitter and receiver must be at least 10
-6
.
However most Amateur Radio and Commercial grade HF SSB transceivers only offer 2.4kHz
filters, typically over the range of 300-2700Hz. Such radios can be used with MS110A at data
rates of 600bps and less on TX and somewhat better on RX when using IF Shift or Passband
tuning to achieve a wider RX bandwidth. Radios that have no IF SHIFT really need to have a