10
Internal AIS / VHF splitter
The M1 incorporates an AIS/VHF splitter to share one AIS/VHF
antenna and to allow connection to an external VHF radio via the
auxiliary port.
The auxiliary port protects the transponder while an external VHF
is transmitting (up to 25W) and also isolates the external VHF
radio when the M1 is transmitting.
The auxiliary port will still provide a path to the antenna for the
external VHF radio in the event of an M1 power failure.
AIS / VHF Antenna (required)
The M1 shares one antenna for both AIS and VHF functions.
A dedicated VHF antenna is required.
Choose a high quality omni-directional VHF antenna designed for
the marine band (156-162MHz) and ensure it is well tuned at the
AIS end of the band (VSWR 2:1 or less at 162MHz).
See Part Number VA159 (AIS/VHF Antenna).
Mount the antenna vertically, as high as possible (at least 2-3
meters (6-10 ft) above the waterline). It is not recommended to
place the VHF antenna near a mast or other metal structures
CAUTION - Install the antenna a minimum of 3m (10ft) from any
other VHF or HF antennas and not within the beam path of a
radar. Inadequate separation may damage the Cortex transponder
and void your warranty.
CAUTION - Never operate the M1 unless it is connected directly
to a suitable VHF antenna.
HINT - The VHF indicator light will display red when a problem
is detected with the antenna system (ie, the VSWR is above the
acceptable level).
> Connect the AIS/VHF Antenna plug (PL259) to the M1 port
labeled ANTENNA.
> Tighten clockwise.
> (If applicable) Connect the auxiliary VHF antenna cable
(BNC) to the auxiliary VHF port labeled SPLITTER.
AIS / VHF Antenna connection
Auxiliary VHF
VHF Antenna
VSWR stands for Voltage Standing Wave Ratio and is a measure
of the how well matched a transmission line (e.g. the antenna
cable connected to the VHF output of your the M1) is to its
termination impedance (e.g. your antenna).
VSWR can be thought of as a comparative measure of how much
power, generated from your M1 AIS transponder, is delivered to
the antenna and how much of it is reflected back and lost in the
poorly matched transmission line.
A high VSWR will reduce your effective transmission range and
may also lead to other problems.
What does VSWR mean ?
