SCS PTC-IIex, Manual

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11 PSK31
155
11.7 Receiver Tuning
A PSK31 signal can be recognized on the spectroscope display by a field of 3-5 brighter
LED´s. A PSK31 signal containing only idles (fill-ups without data) consists of a pure
two-tone signal with a tone difference of 31.25 Hz. On the tuning display, this sort of
signal lights generally only two LED´s relatively brightly, with a separation of 3 LED´s:
If useful data is being transferred, then a PSK31 signal is shown normally as a band of 3
LED´s with heavily fluctuating intensity .
To decode a PSK31 signal, it should be as close as possible to the center of the
spectroscope,i.e. symetrical, centered around the central (8th) LED. If a PSK31 signal is
tuned to within approximately
±
10 Hz of the middle position with the VFO knob on the
transceiver, the squelch opens, and one sees additional LED´s on the tuning indicator
which display the actual demodulated PSK31 signal. These can, like in PACTOR-1 or
RTTY, be carefully tuned with the VFO until, ideally, only the two outer LED´s (1 and
15) flicker.
The fine tuning can also be carried out with the hot-keys <Ctrl-K> and <Ctrl-L> if the
VFO does not have a fine enough resolution. At first sight, the tuning procedure sounds
relatively complex. With a little practice however, the tuning can be carried out almost as
easily as with PACTOR-I or RTTY, despite the comparatively small bandwidth of the
PSK31 signal. The tuning of DQPSK is however markedly more critical compared to that
of DBPSK, and the demodulated (red LED) signals are less clearly defined, so that here
one must pay great attention to the
spectroscope .
11.8 CW-Identification
The CWID of the PSK31 terminal always is activated in the Audio Only mode, i.e. the
PTT is active during the whole time and only the tone signal is keyed according to the
rhythm of the CW characters. The special pulse wave shape of the CW character
generates a relatively narrow spectrum, so that the adjacent PSK31 channels are not
disturbed during the CWID.
The PTC-IIex sends an additional CWID after a PSK31 transmission if the CWID-
Parameter (refer to
CWid
, chapter 6.27 , page 48 ) is higher than 0. If the parameter is
higher than 1, also before each PSK31 transmission a CW identification is sent.