NorthStar GM1708 961X Installation Manual page 53

Table 4: Troubleshooting the radar interface (continued)
Component
RADAR DEVICE
961 INSTALLATION MANUAL Revision A
Symptom
There's bearing-pulse interference
from the radar (this also applies to
depth sounders).
SECTION TWO - Installation
Possible Solutions/Reasons
•
The radar's scanning cables may be too
closely bundled with the 961's control
head-to-processor coax cable: Run the
cables of the radar and the 961 on
opposite sides of the vessel.
•
The 961 display-to-processor coax
cable may be damaged or improperly
terminated. Temporarily substitute a
known-good cable to determine if the
cable is defective.
•
The radar scanner cable may be dam-
aged, improperly terminated, or the sys-
tem/vessel grounds need attention.
•
Ensure that the radar display is properly
grounded to an earth ground.
• There maybe a lack of or improper
shielding for the radar's scanning cable.
Inspect the radar scanning
cable-to-scanner base grounding for a
low impedance connection (less than .5
ohms (1/2) between the display end
and the scanner base termination is
optimal; if it's higher, consult the radar
manufacturers). Shielding material can
be used to attenuate interference
effects. Lead, copper, and Mu metal
(Mu is the most expensive) are all good
choices for flat-sheet shielding. There
are a number of different sheet, strap,
or mesh copper products that can be
purchased off-the-shelf. Also, a tinned
"expando sleeve" type copper braided
strap can be used for shielding cable
bunches as long as it is not exposed to
saltwater or corrosive environments.
There are numerous different sizes of
grounding plates available for installa-
tion outside the vessel hull, in water,
that provide a good "seawater-earth"
grounding plate.
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