Timewave DSP-232, Руководство по эксплуатации

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Chapter 11 SIAM and NAVTEX Operation
Chapter 11
SIAM and NAVTEX Operation
NOTE: The SIAM function is not operatioal in the DSP-232!
Overview
As you tune across the HF bands you’ll find an ever increasing number of digital signals. These signals range from
the simple Murray Baudot code, to ASCII, and even packetized data. With the large number of speeds, formats, and
shifts now in use, it’s sometimes difficult to determine what kind of signal you’re listening to. Even with a
knowledge of digital communications, it’s still time consuming to set the communication parameters correctly by
trial-and-error methods.
Signal Identification and Acquisition Mode (SIAM™) was developed by AEA to allow a wide variety of digital
signals to be automatically analyzed by the DSP. SIAM will listen to a signal for a few seconds then will display the
type of signal it is and its speed. You can then decide whether or not to copy the signal, or move off to find another.
To have copy come up on the screen, type
OK , then press ( RETURN ).
One of the aspects of a transmission that SIAM looks for are its start and stop pulses. With the
asynchronous signals
used by amateur radio operators, the start and stop pulses act as delimiters at the beginning and end of each
character; SIAM looks for these pulses. In the commercial bands, mostly
synchronous signals are used. If you’re
tuned to a synchronous signal, SIAM won’t find the start and stop pulses (or other recurring data patterns) it needs
and will be unable to decode any text.
SIAM can identify and copy ASCII, ARQ and FEC AMTOR, SITOR, and Baudot signals. (At this writing, SIAM
can’t decode Packet, PacTOR and Morse code signals.) Once copy has been identified, you can read it by entering
OK
after the analysis has been completed.
Before proceeding with the rest of this section, review the following commands that are directly applicable to the
SIAM mode:
ARQE , CODE (see Chapter 4) , RXREV , SAMPLE , SIAM , TXREV , and WIDESHIFT . SIAM
commands are listed and explained at the end of this chapter. Terminal Interfacing can be found in Chapter 4.
Setting Up for SIAM
(If you’re using an AEA program, follow the instructions in the program’s manual to setup and use the SIAM
mode.)
To enter the SIAM mode, simply enter
SIAM or SI at the Command prompt. The DSP responds by displaying the
previous mode and it was in, then its new mode:
cmd:
SI
Opmode was (previous mode)
Opmode now SIgnal
cmd:
Look at your DSPs front panel to verify that you’re in the SIAM mode—the ‘S’ will glow in the mode window.
Next, you can choose which modem you want to use using the
MODEM
command, followed by the specific modem
number. For a list of modems available in the DSP, type DIRECT at the
cmd:
.
Reception
September, 05 11-1