ICOM AT-140 User Manual

2

1

ANTENNA SYSTEM

■

Insulate the lead-in cable of the AT-140 antenna ter-
minal and antenna element from other metal objects. 

To prevent interference, keep cables as far as possi-
ble from an antenna, electric pump and other elec-
tronic 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.

■

The AT-140’s ground terminal 

be connected

to your ship’s ground. Grounding prevents electric
shocks, interference to other equipment and other
problems. Grounding also ensures effective signal
transmission.

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 

The mounting plate is 

con-

nected to the AT-140’s internal ground.

One of following points is ideal:
– External ground plate
– External copper screen 
– External copper foil

If electrically connected to sea water, one of the fol-
lowing points is usable:
– Stainless steel stanchion
– Through mast
– Through hull
– Metal water tank

the following points, if possible. These con-

nections may cause noise or electrolysis:
– Engine block
– Ship’s DC battery ground

All ground cables from the AT-140, HF transceiver,
etc. on your ship should be connected to only 1 ship’s
ground.

connection to 2 or more points. Voltage dif-

ference between 2 or more ship’s grounds may cause
electrolysis.

connection between dissimilar metals where

an electric current is present. These connections may
cause electrolysis.

If your ship is made of FRP, etc. and a good ship’s
ground is not available, connect a counterpoise.

1

⁄

4

λ

(quarter wavelength) radial for each band is suit-

able for a counterpoise. Install the counterpoise di-
rectly below the AT-140’s ground terminal. Insulate
the ends of each radial from other metal objects. Lay-
out 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 counter-
poise with the following length: 

For best results, use the heaviest gauge wire or metal
strap available. Make the distance between the AT-
140’s ground terminal and ship’s ground as short as
possible.

Supplied ground cable can be used for ground con-
nection to a through mast. Confirm that the through
mast is electrically connected to sea water.

R

Use a Zinc anode to protect the hull from electroly-
sis.

Ask your technical dealer, installer or refer to a tech-
nical book, etc., for RF ground details.

L

 

=

 

300

16

×

1

4

4.7 [m]

1 m

39 inches

L

 

=

 

300

f

×

1
4

Ground terminal

AT-140

1

⁄

4

λ

 radial for 

each band