How to Properly Construct a Ground System

 

The failure to properly bond radio station equipment and associated antenna grounding systems to the AC entrance grounding electrode is a leading cause of damage to radio equipment, notably in amateur radio installations. The source of such damage from a lightning attachment most often occurs when the strike is to power company or telecommunication equipment. Lightning energy enters the structure on the power company system and exits via communication devices and their coaxial feed lines to an isolated grounding system. Had the system been properly bonded in accordance with codes and standards cited below, there would have been an equipotential condition maintained that would serve to limit such current equalizations at the expense of solid state equipment in it's path.

 

NEC (US National Electrical Code) article 250 (grounding), article 810 (Radio and Television Equipment), and NFPA 780 (Standard for the Installation of Lightning Protection Systems) are all clear on the absolute requirement to bond all grounding systems to the AC service entrance grounding electrode.

 

Surge protection for a coaxial feed line (center conductor) to the radio station can be accomplished by either installing a coaxial surge protector device, or by isolation via fiber optic or high voltage isolation transformers.  However all coaxial shield grounds, antenna mast grounds and the structure AC entrance ground must be bonded for lightning protection safety.

 

Ground-loops that cause impedance imbalances (audio-hum) for audio-visual equipment often tempts installers to isolate these systems from the building ground.  The source of the problem can usually be traced to daisy-chaining ground (bonding) straps or improperly functioning equipment elsewhere in the structure.  It is no favor to the equipment owner for an installer to take short cuts in lightning protection in order to correct an audio-hum issue, the cause of which is not from proper bonding and grounding.

 

Respectfully,

Jack Painter

5th CG District Communications Staff Officer

U.S. Coast Guard Auxiliary Virginia Beach VA

 

This information was originally posted on the LightningProtection Yahoo group. To learn more about this group please visit them online: http://tech.groups.yahoo.com/group/LightningProtection/