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No new message reception
1
Is the vessel within range of a NAVTEX transmitting station?
2
Has there been a scheduled transmission since the NAV-7 was
first switched on?
3
Check that the antenna is clear of obstructions and has not
suffered external damage and that the antenna cable is not
damaged
4
Check that the antenna fault icon is not being displayed on the
status bar at the top of the display
5
View the
Setup mode: Receiver options
screen check
That the correct antenna power setting is selected according to
antenna type fitted, ‘active antenna’ require that the antenna
voltage to be set to; ‘Enable’
6
View the
Setup mode: Receiver options
screen view
the signal strength indicator, a constantly strong reading (no
receive icon displayed) can indicate that a strong local
interfering signal is blocking NAVTEX reception.
Testing a 905-05 tri-channel active antenna active antenna
If it is suspected that reception is being compromised by the antenna performance,
the antenna should be checked for electrical damage.
Disconnect the antenna from the NAV-7 by unscrewing the TNC connector at the
back of the NAV-7.
Using a DVM set on resistance, measure across the TNC RF connector from the
centre pin to the outer ferrule, looking back up towards the antenna.
DO NOT ATTEMPT TO MEASURE THE RESISTANCE
OF THE TNC SOCKET ON THE NAV-7.
A good antenna will show a reading in the range 1500 – 2000 ohms.
A failed antenna will show a reading < 1000 ohms.
If a reading of greater than 5000 ohms is measured, then there is a continuity problem
with the connector or cable; these should be checked for damage or misconnection.
Note that these resistance values only apply to a 905-05 active antenna as supplied
by McMurdo. Other active antennas will have different resistance readings; consult
the supplier in order to check such antennas.
