Coaxial Cable; Ground And Counterpoise - Icom YPL 880 Instruction Manual

n Coaxial 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.
n Ground and counterpoise
Why a ship's ground is required
The AT-141's ground terminal
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
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.
MUST
be connected
NOT
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.
Counterpoise
If your ship is made of FRP, etc. and a good ship's
ground is not available, connect a counterpoise.
1 λ radial for
⁄
4
each band
Ground terminal
AT-141
λ (quarter wavelength) radial for each band is
1 ⁄
4
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]
300 1
L = ×
f
4
[Example]
At an operating frequency of 16 MHz, use a
counterpoise with the following length:
300 1
×
L = 4.7 [m]
16 4
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.
R WARNING!
— When grounding to metal hull
U s e a Z i n c a n o d e t o p r o t e c t t h e h u l l f r o m
electrolysis.
Ask your technical dealer, installer or refer to a
technical book, etc., for RF ground details.
ANTENNA SYSTEM
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