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ANTENNA SYSTEM
nCoaxial cable
Insulate the lead-in cable of the AT-141 antenna
terminal and antenna element from other metal objects.
To prevent interference, keep cables as far as
possible from an antenna, electric pump and other
electronic equipment.
To prevent erroneous indications, keep cables as far
away as possible from the flux gate compass.
Use suitable noise filters for alternators, fluorescent
lights, etc. Ask your Dealer for details.
nGround and counterpoise
Why a ship’s ground is required
The AT-141’s ground terminal MUST be connected
to your ship’s ground. Grounding prevents electric
shocks, interference to other equipment and other
problems. Grounding also ensures effective signal
transmission.
DANGER! NEVER connect the ground terminal
to the following points. These connections may cause
an explosion or electric shocks:
– Gas or electrical pipe
– Fuel tank or oil-catch pan
IMPORTANT! The mounting plate is NOT
connected to the AT-141’s internal ground.
Ideal ground points
One of following points is ideal:
– External ground plate
– External copper screen
– External copper foil
Good ground points
If electrically connected to sea water, one of the
following points is usable:
– Stainless steel stanchion
– Through mast
– Through hull
– Metal water tank
Undesirable ground points
AVOID the following points, if possible. These
connections may cause noise or electrolysis:
– Engine block
– Ship’s DC battery ground
Electrolysis
All ground cables from the AT-141, HF transceiver,
etc. on your ship should be connected to only 1 ship’
s ground.
AVOID connection to 2 or more points. Voltage
difference between 2 or more ship’s grounds may
cause electrolysis.
AVOID connection between dissimilar metals where
an electric current is present. These connections
may cause electrolysis.
Counterpoise
If your ship is made of FRP, etc. and a good ship’s
ground is not available, connect a counterpoise.
Ground terminal
AT-141
1
⁄
4
λradial for
each band
1⁄4λ(quarter wavelength) radial for each band is
suitable for a counterpoise. Install the counterpoise
directly below the AT-141’s ground terminal. Insulate
the ends of each radial from other metal objects.
Layout the radial horizontally and as straight as
possible.
L : Counterpoise length for the operating frequency [m]
f : Operating frequency [MHz]
[Example]
At an operating frequency of 16 MHz, use a
counterpoise with the following length:
L=300
16 ×1
44.7 [m]
1 m 39 inches
Ground cable
For best results, use the heaviest gauge wire or
metal strap available. Make the distance between the
AT-141’s ground terminal and ship’s ground as short
as possible.
Supplied ground cable can be used for ground
connection to a through mast. Confirm that the
through mast is electrically connected to sea water.
RWARNING!— When grounding to metal hull
Use a Zinc anode to protect the hull from
electrolysis.
Ask your technical dealer, installer or refer to a
technical book, etc., for RF ground details.
