6 Commands
82
Parameter: X 0… 99, Value for the noise suppression.
100… 200, used for ZCZC/NNNN autostart.
The trigger point for the software squelch (noise suppression) for Baudot RTTY can be
set using the SQuelch command, with values between 0 to 99. With the value 0, the
squelch is always open (noise-suppression turned off). With the value 99 the squelch is
always closed (all signals suppressed). With a value of about 40, the squelch remains
closed on a totally free channel, but is very sensitive to changes in the signal spectrum on
that channel. Even very weak and noisy RTTY signals should correctly open the squelch,
when it is set to the standard value of 45.
Coastal radio stations or other professional RTTY stations normally send the character
string ZCZC in advance to a new message. The end of a message is followed by the
character string NNNN.
This can be used to make a Start/Stop squelch available. If ZCZC/NNNN is activated the
PTC-IIIusb receive in the Baudot/RTTY mode only if the pattern ZCZC is found in the
data stream. As commercial radio stations only send for a short time at a day, using this
special (digital) squelch can reduce the accidental received QRM drastically.
The ZCZC/NNNN autostart can be activated setting the squelch parameter to a value
between 100 and 200. If the squelch value is set to 140, the PTC-IIIusb operates with the
ZCZC/NNNN autostart and additionally with the normal analog squelch of 40 (value
minus 100). This means that also during open autostart squelch the reception is
interrupted, if the signal falls below a certain level.
6.90 STatus
Default setting: 1
Parameter: 0 Status checking on (see text).
1 Status checking on.
2 Status checking on (automatic status output).
The status word polling in the PTC-IIIusb is permanently turned on. The parameter 0
has only been retained for compatibility reasons.
The status word polling in the PTC-IIIusb is permanently turned on. The status command
has only been retained for compatibility reasons. Any argument is ignored.
This command facilitates polling of all operational states of the PTC via the serial
interface. This is useful for mailbox systems, or more luxurious terminal programs.
The status byte is called by the RS character (ASCII decimal 30). This definition of the
status request byte does not impose any restrictions on data transparency. PACTOR uses
ASCII 30 (decimal) as the idle byte which can only be transmitted via a supervisor
sequence.
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