Timewave DSP-232, Operating Manual

Page: 206 / 271

Chapter 11 SIAM and NAVTEX Operation
To use
SAMPLE
, set
ACRDISP
to a non-zero value such as
77
. This will break up the recorded disk file into lines.
Tune in the signal, set WIDESHFT ON or OFF as needed, and get the transmission rate from the SIGNAL
command. Now type
SAMPLE
(
rate
). As an example,
SIGNAL
may identify a transmission as 96 baud TDM; in
this case, enter the following:
SAMPLE 96
Now begin the “capture to a disk” file command with your terminal program. At the end of the session, edit the
disk file and remove any TNC commands that were echoed before or after the received data.
Occasionally,
SIGNAL will identify a Baudot transmission at a rate that SAMPLE can’t sync with. This will
happen if the Baudot signal has a stop bit duration 1.5 times the data bit duration. In this case,
SAMPLE
at twice
the baud rate and compensate for the doubled data bits in the analysis software. Note that it might be more useful to
let the TNC do the start/stop bit work by using the
5BIT
command rather than
SAMPLE
.
5BIT
uses
RBAUD
, and
adds a constant of hex $40 to each 5-bit character received.
Note :
RXREV
affects the sense of the SAMPLE data; it shouldn’t be changed while capturing data.
SIgnal
Immediate Command
Mode: All Host: SI
SIGNAL
causes the DSP to enter the Signal Identification and Acquisition mode (SIAM). The DSP will respond
with:
Opmode was
(
mode
)
Opmode now SIgnal
After a few seconds the DSP will show the signal’s baud rate. A few seconds after that it’ll try to identify the signal
type. SIAM
can’t identify packet, AMTOR or PACTOR signals.
WIdeshft ON
|
OFF
Default: OFF
Mode: Baudot/ASCII, RTTY, AMTOR, PACTOR Host: WI
OFF RTTY tones are shifted 200 Hz (emulates 170-Hz shift).
ON
RTTY tones are shifted 1000 Hz.
WIDESHFT
permits the use of the DSP on VHF or HF with either wide (1000 Hz) or narrow (200 Hz) shifts. Many
amateur radio VHF and HF RTTY operators use 170-shift. The PK’s 200 Hz shift is well within the filter tolerances
of any RTTY demodulator in general service. MARS stations will find
WIDESHFT
generally compatible with
MARS and Commercial 850 Hz shift RTTY operations.
September, 05 11-7