3. Installation
37
3.4
Rear side configuration switch
This switch has 4 positions with different meanings. All of these can be switched on or off. ON
means that the switch is set to the lower position, OFF is the higher position. When set to ON,
the labeled condition is enabled.
3.4.1
ON switch
In many cases a modem is power-supplied by the radio connected to it (mostly ICOM radios)
and it is desirable, that the modem immediately starts when the radio is powered on. To archive
this, the rear dip switch #1 (labeled with
ON
) must be set. In this condition the PTC-IIIusb is
always on when it has supply power. It cannot be switched off any more with the sensor. The
modem can only be switched off by cutting the external power supply.
3.4.2
BIOS switch
This switch enables the Bootloader of the PTC-IIIusb. The Bootloader allows some of the basic
functions of the PTC-IIIusb to be used and works totally independently from the presently
loaded firmware. The Bootloader has a very basic and essential task, and thus is placed in a
specially protected area of the FLASH memory.
Normally, the user does not need to worry about the existence of the Bootloader. However, due
to various unlucky or exceptional circumstances, it is possible that the PTC-IIIusb will no
longer load the PACTOR firmware. Under these conditions, the PTC-IIIusb can be accessed
via the BIOS.
If, for example, there is a power failure during a normal firmware update, one part of the
FLASH is programmed with the new version, while the other still contains a part of the old
firmware. It is very unlikely that such a mixture will run, and the Bootloader is then the only
way the system can be recovered.
The BIOS is automatically activated as soon as the PTC-IIIusb detects an error on loading the
PACTOR firmware, or the user wishes access to the BIOS by setting the DIP-switch to ON.
3.5
Connections to the transceiver
Due to the variety of possible transceiver types which can be used with the PTC, it is somewhat
more difficult to find out the correct connection. For many common transceivers complete
manufactured cables are available as accessory (chapter 5 on page 49). For all others the
attached DIN-8 pigtail cable must be used and completed by the user. Your dealer will be
helpful to find the proper connection scheme.
PACTOR-II and PACTOR-III use differential phase-modulation (DPSK), 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 3.5.4 on
page 42 for how to set the modulation levels properly.
PACTOR-II and PACTOR-III modulation schemes are totally different to 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-II/III signal must always go the indirect way, which is using the SSB
