ICOM AT-140 User Manual

1

1

■

Required antenna element length to achieve full per-
formance varies according to the lowest frequency: 

The longer the antenna element, the better the an-
tenna efficiency. 

multiples of 

1

⁄

2

λ 

(half wavelength) for an-

tenna element lengths, since tuning becomes difficult.

L : Antenna element length to be avoided [m]
f : Operating frequency [MHz]
n : Natural number (n = 1, 2, 3, ...) 

[Example]
At an operating frequency of 16 MHz, avoid the fol-
lowing antenna element lengths:

For example, if 15 m is selected for an antenna ele-
ment length, you have no problem in the 1.6–25 MHz
marine bands range.

NOTE: Keep antennas as far away from other objects
as possible, especially metal objects.

Insulator

Backstay operates as 
a long-wire antenna.

Insulator

Whip antenna

L

 

=

 

300

16

×

1

2

n

×

9.4, 18.8, ...

1 m

39 inches

L

 

=

 

300

f

×

1

2

n

×

The lowest frequency Required antenna element length

1.6 MHz band

7 m; 23.0 feet or longer

4 MHz band

3 m; 9.8 feet or longer

■

In some countries, HF transceivers can be used for
land mobile operation. Ask your Icom Dealer for de-
tails, since the radio law varies according to each
country.

For land mobile operation on 4 MHz and above, an
optional AH-2b ANTENNA ELEMENT is available.
The AH-2b includes a sturdy tow hook mount system
for holding a 2.5 m; 8.2 feet stainless steel antenna
element plus all the necessary hardware.

Refer to the AH-2b instruction manual for the AH-2b
and AT-140 installation to your vehicle. Ask your Icom
Dealer for details. 

Connect a suitable antenna element for a base sta-
tion. To achieve full performance, refer to “Required
antenna element length” above.

AH-2b