Ground And Counterpoise - Icom AT-130 Instruction Manual

WiCoaxial cable
Insulate the lead-in cable of the AT-130/E antenna ter-
minal 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.
WGround and counterpoise
Why ship's ground is required
The AT-130/E'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
—Oil-catch pan
BE CAREFUL. The mounting plate is NOT connected
to the AT-130/E's internal ground. Non-through mast is
NOT electrically connected to sea water.
Ideal ground points
One of following points is ideal:
—Ship's ground terminal
— External ground plate
— External copper screen
Good ground points
If electrically connected to sea water, one of the following
points is usable:
— Stainless steel tuna tower
— Stainless steel stanchion
—Through mast
— Throughhull
— Metal water tank
Undesireable ground points
AVOID the following points, if possible. These connec-
tions may cause noise or electrolysis:
— Engine block
— Keel bolt
Electrolysis
All ground cables from the AT-130/E, HF transceiver, etc.
on your ship should be connected to only 1 ship's ground.
AVOID connection to 2 or more points. Voltage differ-
ences between 2 or more ship's grounds may cause
electrolysis.
AVOID connections between dissimilar metals where an
electric current is present. These connections may cause
electrolysis.
ANTENNA SYSTEM 1
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 Icom Dealer for details.
Counterpoise
If your ship is made of FRP, etc. and a good ship's
ground is not available, connect a counterpoise.
1/4A radial for
each band
Ground terminal
AT-130/E
1/4A (quater wavelength) radial for each band is suit-
able for a counterpoise. Install the counterpoise directly
below the AT-130/E's ground terminal. Insulate the ends
of each radial from other metal objects. Layout the
radials horizontally and as straight as possible.
L : Counterpoise length for the operating frequency [m]
f : Operating frequency [MHz]
300 1
L= = a
[Example]
At an operating frequency of 16 MHz, use a counter-
poise with the following length:
300 1
L= =. == = 4.7 [m]
1m 39 inches
Ground cable
For the best results, use the heaviest gauge wire or
metal strap available. Make the distance between the
AT-130/E's ground terminal and ship's ground as short
as possible,
Supplied ground cable is usable for ground connection to
a through mast. Confirm that the through mast is
electrically connected to sea water.