SCS P4dragon DR-7800, Руководство по установке

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6. Connectors
70
PACTOR-2/3/4 use complicated phase- and amplitude modulations (DPSK, 32QAM), which
leads to a small and effective spectrum. To maintain the advantages on the HF-frequencies, a
proper adjustment of the transceiver’s settings and modulation levels is essential. Over-
modulating the transceiver would lead to unwanted enlargement of the spectrum. Refer to
chapter 7.3 on page 81 for how to set the modulation levels properly.
PACTOR-2/3/4 modulation schemes are totally different to and have nothing to do with
simple FSK, which was used in older HF transmission modes. It is therefore
IMPOSSIBLE to use the FSK modulator which can be found in some transceivers to
generate the signal. The PACTOR-2/3/4 signal must always go the indirect way, which is
using the SSB modulator to generate the HF signal. This is of no disadvantage, providing
the transceiver is not overdriven.
Some useful hints to properly setup the transceiver:
•
For PACTOR-3/4 use a 2.4 kHz wide IF-filter (usually also used for SSB/voice). Do
not
use a smaller one. If you limit the modem’s operation to PACTOR-2 (e.g. for saving
bandwidth reasons), you can use a 500 Hz IF-filter.
•
Under no circumstances use audio processors. The speech-compressor of the transmitter
will damage the PACTOR signal in the same way as external DSP audio filters will do.
These external DSP audio filters create inpredictable signal propagation delays which are
not acceptable. The modem filters the signal optimal with the integrated DSP and requires
no “external help”.
•
Noise blanker and notch filter should be switched off.
The
P4
dragon
is connected to the transceiver via an 8 pin DIN socket (HF-Transceiver Audio).
Although you can use the
MAIN Audio
or
AUX Audio
connectors the same way, we
recommend to begin with
MAIN Audio
as long as only one radio shall be connected. If you’re
using an ICOM radio, the ICOM also supply the modem via the one or the other connector.
Other radios not supplying the modem will require that the modem is supplied using the
DC-in
screw terminal.
6.2.1 Balanced and unbalanced operation
In difference to earlier
SCS
modems, the
P4
dragon
provides a complete signal separation and
balanced audio in/outputs. Also the PTT is isolated by an optical circuit. The transceiver ports
MAIN Audio
and
AUX Audio
are isolated against each other and also the transceiver control
port is isolated from all the rest. The audio in/outputs are coupled via transformers, which
means that the input and the output consists of two signal lines now. Also PTT consists of two
lines and is a bi-directional switch, which means that it does not care which pin is connected to
high and which to low. As many professional radios also provide balanced, transformer
coupled audio lines, it is recommended to connect the modem respectively to archive best
signal quality and rf immunity.
For all other radios, it is possible to internally ground one leg of the transformers and the PTT
line. This is done with internal DIP switches, for both transceiver ports separately. With this
switches set to
ON
the DR7800 is fully connection compatible with all earlier
SCS
modems,
while maintaining the signal isolation. This is how the
P4
dragon
is delivered by default to the
customer. This means, when true balanced operation is required, the modem must be opened
and the switches must be set to OFF respectively. The picture below shows the location of the
switches and how they are associated to the port connectors.