10 FT-857 Operating Manual
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:
r It can minimize the possibility of electrical shock to the operator.
r 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.
r 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-82 Mounting Bracket will accomplish this, if the
MMB-82 itself 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:
r RF feedback (resulting in distortion on your transmitted signal);
r Unintended frequency change;
r Blinking or blanking of the frequency display;
r Noise pickup; and/or
r Loss of memory.
Note that these conditions may occur in any communications installation. The FT-857 in-
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-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.
INSTALLATION
To Next Page
General
