
ANTENNA SYSTEM | 1 |
■Coaxial cable
Insulate the
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.
■Ground and counterpoise
Why a ship’s ground is required
The
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
Counterpoise
If your ship is made of FRP, etc. and a good ship’s ground is not available, connect a counterpoise.
1⁄4λ radial for each band
Ground terminal
IMPORTANT! The mounting plate is NOT con- nected to the
Ideal ground points
One of following points is ideal:
–External ground plate
–External copper screen
–External copper foil
1⁄4λ (quarter wavelength) radial for each band is suit- able for a counterpoise. Install the counterpoise di- rectly below the
L : Counterpoise length for the operating frequency [m]
f : Operating frequency [MHz]
Good ground points
If electrically connected to sea water, one of the fol- lowing points is usable:
–Stainless steel stanchion
–Through mast
–Through hull
–Metal water tank
Undesirable ground points
AVOID the following points, if possible. These con- nections may cause noise or electrolysis:
–Engine block
–Ship’s DC battery ground
Electrolysis
All ground cables from the
AVOID connection to 2 or more points. Voltage dif- ference 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.
L = | 300 | ⋅ | 1 | |
f | 4 | |||
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[Example]
At an operating frequency of 16 MHz, use a counter- poise with the following length:
L = | 300 | ⋅ | 1 |
| 4.7 [m] |
16 | 4 |
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1 m | 39 inches |
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Ground cable
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.
RWARNING!— When grounding to metal hull 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.
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