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Transmission Modes WAVECOM Decoder W74PC, W-PCI/e, W-CODE, W-CLOUD Manual V9.1.0
MIL-188-110A-MOD
MIL-188-110A-MOD is a modified version of the popular MIL-188-110A mode.
Like MIL-188-110A, this mode employs 8-ary phase shift keying (PSK) on a single carrier frequency (1800
Hz) as the modulation technique for data transmission. The carrier modulation is a constant 2400 Baud
waveform.
Each transmission of a MIL-188-110A-MOD message begins with a 267 ms long synchronization phase
(preamble) followed by the data phase, which is of unlimited length. The data phase is structured in User
Data (20 unknown 8-PSK symbols) – Channel Probe (20 known 8-PSK symbols) pairs.
The MIL-188-110A-MOD decoder demodulates the waveform and displays the raw demodulated output in
HEX format.
Tuning the Decoder
The decoder processes signals in both SSB settings: USB and LSB. This can be selected with Polarity in
the menu: NOR means USB and INV means SSB.
The center frequency of the decoder should be set to 1800 Hz when the receiver is correctly tuned to the
transmitting station. Small frequency variations are automatically compensated in the decoder. The fre-
quency of the decoder can be adjusted to ±400 Hz from its normal settings. By using the bar-graph, any
remaining frequency difference can be compensated by fine tuning of the receiver frequency or by adjust-
ing the center frequency of the decoder.
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