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Interference Problems
Interference can come from several sources. The
most common of these are:
1)
Other nearby depth sounders operating at the
same frequency.
2)
Radiated interference from the boat's
electrical system (alternator, distributor and
spark plugs) or from nearby equipment that
radiates electrical noise.
3)
Conducted interference usually occurs when
the PC/180 shares a 12VDC power lead with
other noisy equipment (i.e.; bilge pumps,
motors, refrigeration systems, autopilots, etc.)
Interference caused by nearby depth sounders
operating on or near the same frequency as the PC/
180 will typically appear as "rabbit tracks" that
march up and down the screen. Reducing the gain
will help minimize this problem.
Radiated interference caused by the boat's engine
can usually be identified by observing the PC/180
with both the engine running and turned off. If the
interference disappears when the engine is turned
off, it is safe to assume that the engine is the
source of the interference.
This type of interference can usually be eliminated
by using the same techniques used in the
automotive industry to eliminate interference to car
radios, CB's, etc. The following actions may be
required:
1)
Reduce the Gain setting to minimize
interference.
2)
Make sure your boat uses resistor type spark
plugs and plug wiring.
3)
Install a suppressor on the center lead of the
distributor.
4)
Install an alternator filter to smooth the
alternator's output signal.
Interference may also be caused by radiation from
other nearby equipment and can be detected by
turning off all other equipment and observing the
PC/180 display as each suspected source is turned
back on. This type of interference can usually be
eliminated by moving the PC/180 Acoustic
Interface Module away from the source and
checking to ensure that the interfering source is
properly grounded.
Interference causing the display to be unstable, to
pulsate or periodically change size is usually
caused when another piece of equipment shares the
same 12 VDC power leads from the battery. This
problem is especially severe when equipment
requiring large current surges (i.e.; autopilots,
refrigerators, or bilge pumps) share the same
power leads. Minimize this type of interference by
running the PC/180's 12VDC power leads, or
those of the interfering equipment, directly to the
battery.
Alternatively, you may find it helpful to install a
separate dedicated power supply battery that is
used only to run your electronic gear (e.g.;
fishfinders, VHF radios, radar units, etc.). If your
unit shuts off during low voltage situations, such as
when cranking your engine starter, you may want
to install an isolator switch with an "A/B" type of
battery system. An "A/B" system allows you to
run your electronic gear on one battery, while the
starter and alternator are hooked up to the other
battery.
Your authorized marine electronics dealer is
familiar with the methods of reducing electrical
interference and is qualified to assist you should a
problem persist.
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