FCC ID: K66FT-857
Operating Manual
Vertex Standard Co., Ltd.
6
Grounding
The provision of an effective ground system is important in any successful communications station. A good ground
system can contribute to station efficiency in a number of ways:
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It can minimize the possibility of electrical shock to the operator.
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It can minimize RF currents flowing on the shield of the coaxial cable and the chassis of the transceiver which may
cause interference to nearby home entertainment devices or laboratory test equipment.
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It can minimize the possibility of erratic transceiver operation caused by RF feedback or improper current flow
through logic devices.
An effective earth ground system may take several forms; for a more complete discussion, see an appropriate RF
engineering text. The information presented below is intended only as a guideline.
Inspect the ground system – inside the station as well as outside – on a regular basis so as to ensure maximum
performance and safety.
Mobile Station Grounding
Although satisfactory grounding in most installations will be achieved via the DC cable’s negative lead and the antenna
system’s coaxial cable shield, it is often recommended that you provide a direct ground connection to the vehicle chassis
at the mounting location of the transceiver (installation using the MMB-** Mounting Bracket will accomplish this, if the
MMB-** itself is mounted to the vehicle’s chassis). Due to unexpected resonance which may naturally occur in any
location, improper communication system performance may result from insufficient grounding. These symptoms may
include:
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RF feedback (resulting in distortion on your transmitted signal);
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Unintended frequency change;
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Blinking or blanking of the frequency display;
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Noise pickup; and/or
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Loss of memory.
Note that these conditions may occur in any communications installation. The FT-857 includes extensive filtering
designed to minimize the chance of such problems; however, random currents set up by insufficient RF grounding can
nullify such filtering. Bonding the rear panel Ground lug of the FT-857 transceiver to the vehicle or vessel’s ground
system should clear up any such difficulties.
Vertex Standard does not recommend the use of “on glass” mobile antennas unless the shield of the coaxial cable is
securely grounded near the feedpoint of the antenna. Such antennas frequently are responsible for the ground-related
difficulties described above.