Stanag-4481-fsk, Stanag-4481-psk – Wavecom W61PC V7.5.0 User Manual

Page 235

WAVECOM Decoder W61PC/LAN Manual V7.5

Transmission Modes

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In the HEX display mode, the decoded binary data is just displayed as it is (MSB first).

In the ASCII SYNC mode, each 8 bits (LSB first) represent one ASCII character. The display will stop if the
EOM pattern is received or if more than 20 NULL characters are received.

There are two ASCII ASYNC display modes. In the first format (just named ASCII ASYNC) the 8 data bits
are preceded by one start bit (0) and followed by at least one stop bit (1). The 8 data bits (LSB first) form
an ASCII character. The second format (ASCII ASYNC, 7 Data bit, 0 Stop Bit) displays a 7-bit ASCII char-
acter (LSB first) which is preceded by one start bit (0). There is no stop bit in this format. In both modes
the decoder will stop displaying, in addition to upon receiving the EOM pattern, when more than 300 NULL
characters are received, when the async data structure is violated more than 80 times or the EOM bit pat-
tern is received.

Tuning the decoder

The decoder processes signals in both SSB settings, USB and LSB. This can be selected with the Polarity
setting in the menu: NOR will select USB and INV will select LSB.

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 tracked and compensated for in the de-
coder. The center frequency of the decoder can be adjusted to ± 400 Hz from its normal setting. By using
the bar graph, any remaining frequency difference can be compensated for by fine-tuning of the receiver
frequency or by adjusting the center frequency of the decoder.

Related mode

MIL-188-110A

STANAG-4481-FSK

STANAG-4481 is a synchronous FSK mode, which uses KG-84 encryption for communication. It is com-
monly found in the HF band. A number of communication parameter settings are possible, but 75 Bd and
a shift of 850 Hz are widely used.

Parameter

Value

Frequency range

Operation modes

Broadcast/Simplex FEC

Modulation

FSK

Baud rate

75, 100, 150, 300, 600 Bd

Receiver settings

Data, CW, USB, LSB

Signal source(s)

AF, IF

The KG-84 bit stream contains a 64 bits long header followed by two 256 bit message blocks in turn fol-
lowed by encrypted data terminated by an End-Of-Message. Hence synchronization can only be achieved
at the start of transmission using the KG-84 header.

The length of a message is variable. Messages are usually sent consecutively with a short idle sequence
between each message.

STANAG-4481-PSK

This STANAG mode is specified by the NATO (North Atlantic Treaty Organization) Military Agency for
Standardization as a "Minimum technical equipment standards for naval HF shore-to-ship broadcast sys-
tem".