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Re: [TenTec] Re. [Ten Tec] Grounds

To: tentec@contesting.com
Subject: Re: [TenTec] Re. [Ten Tec] Grounds
From: Stuart Rohre <rohre@arlut.utexas.edu>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Tue, 24 Jan 2012 14:47:42 -0600
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
Technically, a ground wire covered by the deck is a violation of the 
National Electrical Code.  Likely the rod was there first, and the deck 
was built over it.

Breaker boxes, switched disconnects, panel boards and ground rods must 
be accessible for inspection and repair.  It is common for ground rod 
connections to get disturbed by ground shifting, hit by grounds keeping 
equipment, etc. and thus require the clamp to be tightened over time.

The typical house or ham ground rod does little to improve your RF 
performance, as the inductance of the long lead between the shack ground 
bus and the electrical entry ground rod will often mean you have a 
quarter wave situation at the high bands, ie high impedance at one end 
where your rig connects.

Better to put a buried halo ground around the house outside the 
foundation, and connect, (bond) both electrical grounds and the 
communications grounds, as well as ham radio ground to it.

That way, you have provided a physically short path to earth from any 
place in the house where the shack might be.

Be aware however, everything bonded together, with the case of a less 
than good conducting earth, that you could have a hit on an antenna mast 
or tower, bonded to the common bus. The whole of the bonded system will 
rise to a very high potential, and might conduct harmful currents into 
equipment bonded to everything else.  We had this happen at the club 
station:  tower was hit, current came in on shields of coax, (coax was 
INSIDE the tower), and continued into the shack where it went around the 
room on our bus bar, up into a VHF radio, and vaporized the circuit 
board negative power trace before arcing through the power supply to the 
AC third pin ground path back to the AC utility ground.
The ground bus was L shaped around two sides of the room and on the 
short side went out to a metal water supply piping system.  Everything 
was bonded to it with wide flat conductors, thus low inductance.

All AC outlets were bonded by the AC wiring (3 wire plus conduit).
Sometimes it is just going to get you if equipment is left plugged in.

Stuart Rohre
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