The RF gain is set correctly, and AGC is on (fast/slow if appropriate).
The volume control is high enough to be heard.
The loudspeaker is switched-on (if not listening on headphones/
handset).
And, on the DSC unit:
The daily internal test is carried out at the designated time.
The DSC controller is not showing any errorlfault messages.The MF /HF scanning receiver is set to scan appropriate frequencies
for your Sea Area of Operation (allowing for watches being maintained
on other equipment, like the SafetyNET receiver).- Your position is being kept up-to-date and clock time is set correctly
for your time zone.
SSB antennas
The antenna arrangement shown in figure 7.2 is just one of a
number of possible arrangements suitable for SSB radio operation. Using
two antennas, as shown in figure 7.2 - on a two-frequency channel (e.g.
for a link call through a Coast Radio Station) would allow you to have a
'Full Duplex' conversation - meaning that you could keep the PTT switch
pressed and have a normal conversation (i.e. the listener can interrupt
the talker - and probably will).
All inter-ship channels are single-frequency channels (i.e. the same
frequency is used for transmitting and reception - as on 2182kHz) in
which case you can only have a 'Simplex' conversation, even if you
have two antennas. In Simplex communications, only one person can
talk at a time and you have to release the PTT switch before you can
hear the other person talking (remembering to say Over before you
release the PTT switch so that the other person knows that it is their turn
to speak).
Many modern SSB installations only have a single antenna for
both transmission and reception. With a Single antenna, even where you
have separate transmit and receive frequencies, only one person can
speak at a time. Using a Simplex radio installation on a two-frequency
(duplex) channel is sometimes referred to as semi-duplex, or half-duplex.
Figure 7.2 shows the whip antenna being used for reception and
the wire antenna being used for transmission. The two antennas could
have been reversed, in which case the ATU/antenna coupler would have
been fitted to the whip antenna. The ATU may be below deck or above
deck. When fitted below deck, the ATU-to-antenna cable must be wellMARINE COMMUNICATIONS 147