Vertex Standard FT-857 manual Mobile Station Grounding

INSTALLATION

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:

rIt can minimize the possibility of electrical shock to the operator.

rIt 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.

rIt 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-82Mounting Bracket will accomplish this, if the MMB-82itself is mounted to the vehicle’s chassis). Due to unexpected resonances which may naturally occur in any location, improper communication system performance may result from insufficient grounding. These symptoms may include:

rRF feedback (resulting in distortion on your transmitted signal);

rUnintended frequency change;

rBlinking or blanking of the frequency display;

rNoise pickup; and/or

rLoss of memory.

Note that these conditions may occur in any communications installation. The FT-857in- cludes extensive filtering designed to minimize the chance of such problems; however, ran- dom currents set up by insufficient RF grounding can nullify such filtering. Bonding the rear panel Ground lug of the FT-857transceiver 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.

10 FT-857 Operating Manual