[TowerTalk] A unique and difficult grounding problem

[Jim Brown]

On Fri,6/5/2015 9:33 PM, Roger (K8RI) on TT wrote:
> There is a problem with the best approach.  I agree with it in 
> principle, but In over half, ...well over half the installations I've 
> seen in over 54 years as a ham the best approach is not practical, 
> either from a logistics, and or cost approach. 

Brown's Rule: Never let the perfect be the enemy of the good.

W4TV articulated an excellent approach that I implemented in the 
outbuilding that houses my shack, and that is fed from my house. That 
is, there is a half perimeter ring that runs from the power panel around 
one side of the building to my shack, with rods at both ends and along 
the perimeter. That ring is tied to my coax entry panel, and also to the 
operating position ground and to EMT conduit on the station side of the 
building. At the power panel side of the building, it's tied to the 
panel ground.

My two towers are 200+ ft and 120 ft from my shack. They have multiple 
ground rods around the base,  but the only ground tie from them to the 
shack is the coax.  Remember -- lightning is an RF event, NOT a DC 
event, so the dominant parameter of bonding between parts of a system is 
the INDUCTANCE, NOT the RESISTANCE.

Also -- remember that what arrestors like Polyphaser do is SHORT the 
CENTER to the SHIELD in a strike, which minimizes the DIFFERENTIAL 
voltage at the equipment input. But it is the BONDING architecture that 
conducts the strike away from our equipment, AND minimizes the 
DIFFERENCES in potential from one piece of gear to another. Shunt mode 
surge protectors (MOVs) are the ENEMY, because they conduct strikes to 
the Green wire, and the DIFFERENCE between the chassis of unit A and the 
chassis of unit B blows up the interface between them when a strike 
happens. THAT'S why the Ethernet cards in computers fry with a strike. 
Many of my pro audio colleagues with no radios at all have had that 
happen, and that's why the pro audio world has long championed SERIES 
MODE surge suppression.

73, Jim K9YC