Icom AT-140 - Manual (Page 4)

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ANTENNA SYSTEM
■ Antenna for ship
Required antenna element length
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.
Undesirable antenna element lengths
AVOID
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
■ Antenna for land operation
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