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Monday, April 9, 2012

Why Ground

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:
  1. It can minimize the possibility of electrical shock to the operator.
  2. It can minimize RF currents flowing on the shield of the coaxial cable and the chassis ofthe transceiver which may cause interference to nearby home entertainment devices or laboratory test equipment.
  3. 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. 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. Due to unexpected resonances which may naturally occur in any location, improper communication system performance may result from insufficient grounding. These symptoms may include:
  1.  RF feedback (resulting in distortion on your transmitted signal);
  2.  Unintended frequency change;
  3.  Blinking or blanking of the frequency display;
  4.  Noise pickup; and/or
  5.  Loss of memory.
Base Station Grounding

Typically, the ground connection consists of one or more copper-clad steel rods, driven into
the ground. If multiple ground rods are used, they should be configured in a “V” configuration,
and bonded together at the apex of the “V” which is nearest the station location. Use a
heavy, braided cable (such as the discarded shield from type RG-213 coaxial cable) and
strong cable clamps to secure the braided cables to the ground rods. Be sure to weatherproof
the connections to ensure many years of reliable service. Use the same type of heavy, braided
cable for the connections to the station ground bus (described below). Do not use gas line pipes in an attempt to provide a ground connection! To do so creates a serious risk of explosion!!

Inside the station, a common ground bus consisting of a copper pipe of at least 1” (25 mm)
diameter should be used. An alternative station ground bus may consist of a wide copper
plate (single-sided circuit board material is ideal) secured to the bottom of the operating
desk. Grounding connections from individual devices such as transceivers, power supplies,
and data communications devices should be made directly to the ground bus using a heavy,
braided cable. 

Do not make ground connections from one electrical device to another, and thence to the
ground bus. This so-called “Daisy Chain” grounding technique may nullify any attempt at
effective radio frequency grounding. See the drawings below for examples of proper and
improper ground connections.


So, make sure you setup a proper grounding for your shack or mobile station !

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