Interphace ULTRASCAN PC90 Operation Manual Download

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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 Ultrascan PC90 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
Ultrascan PC90 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 Ultrascan
PC90 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
Ultrascan PC90 display as each suspected source is

turned back on.  This type of interference can
usually be eliminated by moving the Ultrascan
PC90 Beamformer 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 Ultrascan PC90’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.