11 PSK31
159
In practice it has been found that an activated NET operation gives little or no
problems. (A note concerning this can be found in the original G3PLX documentation,
available on the internet). The PTC-IIIusb acknowledges the command with “
***
NET: ON
” or “
*** NET: OFF
”. The default setting is NET active.
Ctrl-F:
Sets the receive and transmit carrier frequency to the default value
((MARK+SPACE)/2). This function is only allowed (or possible) in the receive
condition. The PTC-IIIusb acknowledges the command with “
*** RX/TX-
Frequency reset to: 1300 Hz
”
Ctrl-B:
Cycles between the operating modes DBPSK, DQPSK and inverted DQPSK.
If a DQPSK variant is chosen, the PTC-IIIusb signals this with the DQPSK LED.
Inverted DQPSK is needed when lower sideband is used on an SSB transceiver, as
here the signal phasors revolve anti-clockwise, and thus build up a false delta-phase
association for the values 90 and 270 degrees. If DQPSK is used in LSB, then the
inverted DQPSK must be chosen. For USB the normal DQPSK setting must be used
(for compatibility with the other PSK31 users).
The PTC acknowledges the command with: “***
PSK31
-Mode: DBPSK”
or
“
***
PSK31-Mode: DQPSK
” or “
*** PSK31-Mode: inverted DQPSK
”.
CHOChr:
Generally <Ctrl-Y>, refer to
CHOChr
command, chapter
.
Serves to switch between receive and transmit.
QRTChr:
Generally <Ctrl-D, refer to
QRTChr
command, chapter
, page
. Can
also be used instead of
CHOChr
as the final character of a PSK31 transmission.
A PSK31 transmission can be broken off at any time with the
DD
-command.
DD
sets the
system back into the normal STBY-mode. The PSK31 receive condition can be left by
using the
Disconnect
or
Quit
command. In the PSK31 transmit condition, both these
commands act as a normal closedown (identical to the
QRTChr
) of a transmission.
The Hot-keys have priority in the PSK31-terminal mode. This means that no codes
should be chosen for the
CHOChr
,
ESCchr
and
QRTChr
being similar to the hot-
keys, otherwise the
CHOChr
,
ESCchr
and
QRTChr
will not operate in PSK31 mode
One exception from the rule above is the ESCAPE-character (
ESCchr
)
. The ESCAPE-
character has always priority over the PSK31-hot-keys! This convention ensures that it is
always possible to leave the PSK31 mode and return to the command-mode (
cmd:
).
11.7
Receiver Tuning
With the PSK31 terminal activated, the QUAL and LOCK / TUNE - LEDs serve as
tuning indicator. This tuning indicator is only working when the signal to be decoded fits
within a range of ± 100 Hz around the center frequency. It is recommended to use a small
IF filter in the radio to pre-select the input signal.
The QUAL LED is lit permanently
red
for
frequency too low
or the TUNE LED for
frequency too high
. Carefully dialing the VFO knob into the
correct
direction decreases
the frequency offset. When the offset is below ± 15 Hz, the PTC-IIIusb automatically
synchronizes to the signal and starts to decode. The QUAL and LOCK / TUNE - LEDs
start to flicker alternatively in the rhythm of the PSK31 signal. Flickering
red
means that
