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Firmware Update Information 2.7

v2_7_news.eng.txt — Plain Text, 14Kb

Dateiinhalt


                Update Information for Firmware Version 2.7
                ===========================================

The main feature of the firmware version 2.7 is the PSK31-Terminal.
Additionally, there are a few improvements as well as the usual round of
bug-catching.

1. New features
---------------

- PSK31-Terminal
- ZCZC/NNNN-Autostart/Stop for Baudot-RTTY
- Preamplifier switching with R&S-Transceivers XK-2000
- Direct channel selection through the PTC-Scanner with YAESU-Transceivers


1.1 PSK31-Terminal
------------------

1.1.1 General
-------------

The PSK31 system developed by Peter Martinez, G3PLX, offers the RTTY
enthusiast a modern variation to this by now somewhat old fashioned
operating system. It has markedly reduced bandwidth requirements and a
better resistance to interference.

The operating technique is very similar to the normal operation of Baudot-
RTTY, although a more sensitive fine-tuning is required compared to the
older system, as a PSK31 signal requires a tuning accuracy of a few Hertz.

Technically, the system is a differentially phase modulated, single carrier,
with a Baud rate of 31.25 steps per second. In practice, DBPSK and DQPSK are
employed, but with a heavy leaning towards DBPSK. DQPSK, despite the use of
Convolutional Coding (k = 5), has shown itself to be more prone to errors at
very low SNR's compared to uncoded DBPSK.
The waveform pulse of PSK31 is the "Raised Cosine in time" so that the DBPSK
signal switches between two-tone (when only phase changes are taking place)
and a plain single tone carrier. The bandwidth between the first null points
of the spectrum is 62.5 Hz.

A speciality of PSK31 is that it allows the entire ASCII character set, even
the "back space" character is included.

1.1.2 Activation and use of the PSK31 terminal
----------------------------------------------

The command to activate the PSK31 mode is:-

PSKTerm
-------

in the cmd:-menu. Command parameters are not required, and will be ignored
if given. After turning on the PSK31 terminal, the PTC-II is in the receive
condition. Various PSK31 relevant settings are at their default or previously
set values.

The Quit command closes the PSK31 terminal, and returns to the normal STBY
condition. (See below for further info)

Text input may be carried out whilst in the receive condition, and is placed
in the type-ahead buffer. (This can be deleted at any time with CTRL-X see
below.)

The alpha-numeric display shows "PSK31 1300", where the number 1300 is the
receive carrier frequency used. (= the center frequency of the audio signal).

The tuning indicator takes on a different look. It has been changed to a small
"spectroscope", so that the small band PSK31 signals can be tuned precisely to
the correct frequency. Each LED represents the power in a 9.375 Hz wide fre-
quency window. The "spectroscope" encompasses a frequency range of approx.
140 Hz. Lower frequencies are to the right, higher to the left. This is, at
first sight, intuitively wrong. It does however make it easier to tune when
using the usually clockwise turning VFO control of the modern transceiver. The
brighter the LED glows, the higher the energy content within that appropriate
window. See below on how this display may be used to tune in PSK31 signals.

1.1.3 Carrier Frequencies
-------------------------

The audio carrier frequency for receive and transmit are calculated using the
settings for MARK-frequency+SPACE-frequency/2. If one has MARK=1400 Hz and
SPACE=1200 Hz, then the carrier frequency is 1300 Hz. A special command for
the PSK31 AF-carrier frequency is thus not required. The transceiver connected
to the PTC-II can operate with the same settings as for PACTOR or AMTOR etc.
The PSK31 carrier, when correctly tuned, lies exactly in the middle of the IF
filter passband.

When the squelch is open (see below), the PTC-II adjusts the receive carrier
frequency slowly (max approx +- 1 Hz / 5 sec) automatically. to match that of
the received signal. A manual drift correction is not required. See also "NET"
operation and the "Hot-keys".

1.1.4 Level Setting
-------------------

The PSK31 output level (Transmit level) may be adjusted with the FSKA-command.
Normally however, the levels previously set for PACTOR/AMTOR operation can be
used, as the PSK31 peak power is the same as that produced for FSK operation.
As however the amplitude is not constant, the transmitter must on no account
be over-driven! otherwise an EXTREMELY wide spectrum is produced.

1.1.5 Prompt and Status
-----------------------

The usual Baudot-RTTY prompt is displayed, except that a "P" is used as an
abbreviation: **-P-** (SCSP):>
(here, "SCSP" is the AMTOR-selcal. This prompt addition is only displayed
for compatibility reasons).
The expanded command prompt in terminal mode 5 (see TERM-command) has the
code "cmd:" 5, or binary 00100101.
In the "status-byte" see Status-command), the PTC displays RTTY/CW as there
are no further free codes available here to be used.

1.1.6 Hot-keys
--------------

Control of the PSK31 terminal operation is done (as with the CW-terminal) with
so-called "Hot-keys". These are specially defined control codes produced with
the <Strg>-key (or <CTRL>-key).

CTRL-L   : The Receive-carrier frequency is increased by 1 Hz.
            (Only in the receive condition)

CTRL-K   : The Receive-carrier frequency is decreased by 1 Hz.
            (Only in the receive condition)

CTRL-X   : Erases the Transmit (or type-ahead) buffer.
            (The PTC acknowledges the command with "*** CLR".

CTRL-C   : Switches the Squelch between normal operation and continuously
           open. In normal operation, it is possible for even very weak
           PSK31 signals to open the squelch. Switching to continuously
           open (Garble on the screen, even when no PSK31 signal is
           present) should only be necessary in exceptional circumstances.
           When the Squelch is open, the tuning indicator displays in
           addition to the "spectroscope" the actual demodulated PSK31
           signal in red. In addition, the "Idle", "Traffic" and "Error"
           LEDs light up accordingly.

           The PTC-II acknowledges the command with "*** SQUELCH: ON" or
           "SQUELCH: OFF". Default value: Squelch in normal condition
           (=ON).

CTRL-N   : Switches the "NET" operation off or on again. This is a PSK31
           specific function, which has been developed due to the very
           small bandwidth, and the therefore essential automatic
           adjustment of frequency required. "NET" operation means that
           both the receive and transmit frequencies are automatically
           adjusted to that of the incoming signal. Even after a long
           transmitting period there is generally no frequency jump between
           the QSO partners in question. Manual intervention is thus kept
           to an absolute minimum during the entire QSO. If both, (or
           more) QSO partners have "NET" activated, then it is possible that
           the entire QSO slowly drifts over the band from over to over,
           always in the same direction.
           If such an effect occurs, then only ONE QSO partner should have
           "NET" turned on. With "NET" non active, the PTC-II adjusts only
           the receive frequency, and displays this with an exclamation
           mark in the alpha-numeric display just before the frequency.

           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-II 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-II acknowledges the
           command with "*** RX/TX-Frequency reset to: 1300 Hz". (or
           whatever frequency is in use).
           This function is performed automatically after 5 minutes of
           continuously closed squelch.

CTRL-B   : Cycles between the operating modes "DBPSK", "DQPSK" and
           "inverted DQPSK". If a DQPSK variant is chosen, the PTC-II
           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. See CHOChr-command. Serves to switch between
            receive and transmit.

QRTChr   :  Generally CTRL-D, see QRTChr-command. Can also be used instead
            of CHOChr as the final character of a PSK31 transmission.

IMPORTANT:  The "Hot-keys" have priority in the PSK31-terminal mode. This
means that no codes may be chosen for the CHOChr or QRTChr which are also
used by the "Hot-keys", otherwise the CHOChr or QRTChr functions will not
work in the PSK31 terminal mode.

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.

1.1.7 Receiver Tuning
---------------------

A PSK31 signal can be recognized on the "spectroscope" display by a field
of 3-5 brighter green LEDs. A PSK31 signal that contains only idles (fillup
characters i.e. 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 LEDs relatively brightly, with a separation of 3 LEDs:

+ + + + + @ + + + @ + + + + +

If useful data is being transferred, then a PSK31 signal is shown normally
as a band of 3 LEDs with heavily fluctuating intensity .

+ + + + + + @ @ @ + + + + + +

To decode a PSK31 signal, it should be as close as possible to the center
of the spectroscope,i.e. symmetrical, 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 red LEDs 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 LEDs (1 and 15) flicker
red.

@ + + + + + @ @ @ + + + + + @

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.

1.1.8 CW-Identification
-----------------------

The CWID is activated if the CWID-Parameter (cmd:-menu) is higher than 0.
The PTC-II sends an additional CWID right before any PSK31-Transmission
if the CWID-Parameter is higher than 1. Due to special impulse shaping, the
spectrum of the CWID is quite narrow.


1.2 ZCZC/NNNN-Autostart for Baudot-RTTY
---------------------------------------

Shore stations and other commercial broadcast RTTY stations usually transmit
the sequence ZCZC as an indicator for "start of transmission" and NNNN as stop
sequence. This can be exploited for a digital squelch function and helps to
reduce "garbage" on the screen due to reception of noise or unwanted trans-
missions.

The digital Autostart-Squelch can be activated by setting the SQuelch-Para-
(in cmd:-menu) to values higher than 99 (range: 100-200). The overall range
of the SQuelch-Parameter was extended to 0-299. The normal analogue RTTY
squelch function is still available and can be used in conjunction with the
digital squelch.
(A value of 140 yields a normal analogue squelch sensitivity of 40 compared
to the range below 100.) The digital squelch overrides the analogue squelch
component.


1.3 Preamplifier Switching with R&S-Transceivers XK-2000
--------------------------------------------------------

If a frequency string (after direct input with the F-Command in trx:-menu or
from the channel / scanner list) is sent to the transceiver XK-2000, the PTC-II
automatically switches on the HF-Preamplifier of the TRX in case the frequency
is above 20 MHz, and switches the HF-Preamp off in case the frequency is below
(or equal to) 20 MHz.
This automatic switching can be overridden by a string defined in the comment
fields of the channel list (available for each channel). The sequence #:V0
tells the PTC that the HF-Preamp of the TRX should be switched off, the se-
quence #:V1 causes the PTC to switch on the Preamp of the TRX.


1.4 Direct Channel Selection through the PTC-Scanner with YAESU-Transceivers
----------------------------------------------------------------------------

If the TRX-Type is set to YAESU, all frequencies (in the channel list or di-
rectly given from the keyboard) below 100 Hz (eg 0.099 kHz) are interpreted as
a channel number. The PTC then does not send the original frequency string to
the TRX but sends the command "recall memory".
Thus predefined channels (including sideband selection and preamp selection,
etc) can be chosen through the PTC-II.


2. Other Improvements and Bug-Fixes
-----------------------------------

* Bug fixed that caused improper function of the Check command (via HF-Port).

* "Timing" of the multi-tasking slightly changed.

                                     ***

Have lots of fun with the new firmware and PSK31!

73's

Peter, DL6MAA, and the PACTOR team.


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