User's Manual Part 2

30
ANTENNA INSTALLATION
Selecting a suitable antenna
The NAV-7 receives transmissions on three frequencies. 518 kHz transmissions are
in International English; 490 kHz and 4209.5 kHz transmissions may be in a local
language.
To receive on all frequencies the NAV-7 must be used with a wide frequency
(400kHz to 5MHz) antenna that covers 518 kHz, 490 kHz and 4209.5 kHz.
If you have purchased the NAV-7 receiver without an antenna then a suitable active
NAVTEX antenna should be used. McMurdo supplies a suitable wide frequency
antenna with the NAV-7 System; this antenna can be purchased separately as Part
No. 905-05.
If the Installer is supplying an alternative antenna, note that the NAV-7 must
be used with a low impedance 50 ohm antenna or an antenna with a 50 ohm
matching network. A mis-matched or high impedance whip or wire antenna
should not be used as the operational range of NAVTEX reception may be greatly
reduced; it is also important that the antenna is capable of reception over the
frequency range specified above.
If a Wire or long whip antenna is used with the NAV-7 it must be fitted with a 50
ohm matching transformer. Take care that the antenna power is disabled – refer to
Setup – Receiver mode for details. A qualified installer should be consulted.