Mil-188-110A - Wavecom W74PC Manual

start and stop bits, as well as the special "null" characters, inserted by the modem and not being part of
the data stream, are ignored by the display.
The decoder stops displaying data after the EOM sequence is received and goes to Sync state and resyn-
chronizes.
In Options/Frame Format the user data rate and interleaver length can be set.
In Options/Diversity a value between Time / Frequency and Frequency Only diversity can be select-
ed. The value must be set correctly for all user data rates except 2400 and 1200 bps.
In Options/Message Type all the different character lengths and number of extracted data bits can be
set.
Tuning the decoder
The Polarity of the decoder should be set according to the signal. When the received signal is in NOR po-
larity (USB), the Doppler frequency should be tuned to 393.75 Hz using the Offset, all the 39 tones are at
the right side of the Doppler tone; when the signal is in INV polarity (LSB), the Doppler frequency should
be tuned to 3206.25 Hz using the Offset, with all the 39 tones at the left side of it.
The correct decoding process is indicated by a Confidence value, with 100 for a 100% correctly decoded
message. However, finally getting a useful data output can only be achieved by selecting the proper mes-
sage type, frame format (user data rate / interleaver), diversity and signal center.

MIL-188-110A

MIL-188-110A Serial (single tone) is one of the most popularly used modes in long-haul HF data modems.
The mode is specified by the US Department of Defense (DoD) in the "Military Standard Interoperability
and Performance Standards for Data Modems" (30. Sept. 1991).
Parameter
Frequency range
Operation modes
Modulation
Symbol rate
Center frequency
Receiver settings
Input format(s)
This mode employs 8-ary phase shift keying (PSK) on a single carrier frequency (1800 Hz) as the modula-
tion technique for data transmission. Serial binary information (raw data) accepted at the line side input is
converted into a single 8-ary PSK-modulated output carrier. The modulation of this output carrier is a con-
stant 2400 Baud waveform regardless of the actual user data rate.
MIL-188-110A single tone waveform has the following characteristics:
Baud- User data
rate rate (bps)
2400 4800
2400 2400 (Data)
2400 2400 (Voice)
2400 1200
2400 600
2400 300
2400 150
188  Transmission Modes
Value
HF
Unprotected/FEC
8-PSK
2400.0 Bd
1800 Hz
DATA, CW, LSB or USB
AF, IF
FEC cod- Interleaver
ing rate
No coding ZERO (No interleaver)
1 / 2 SHORT or LONG
1 / 2 SHORT
1 / 2 SHORT or LONG
1 / 2 SHORT or LONG
1 / 4 SHORT or LONG
1 / 8 SHORT or LONG
WAVECOM Decoder W74PC, W-PCI/e, W-CODE, W-CLOUD Manual V9.1.0
No. of unknown 8- No. of known 8-
phase symbols, phase
(User Data) (Channel Probe)
32 16
32 16
32 16
20 20
20 20
20 20
20 20
symbols,