[TowerTalk] FIRST TOWER & 2ND FLOOR SHACK --HELP

[Jim Brown]

On 8/8/2013 7:14 AM, Earl Morse wrote:
>   My own are located where the coax penetrates from outside to inside the building. The point was that they need to be put at the "boundary" between "in the shack" and "outside the shack".

You're confusing bonding of the coax shield to ground, which is 
important, with protection of the electronics, which is also important. 
Bonding should ideally be done where the coax enters the building, but 
if there's significant distance between there and the electronics (as in 
the original poster's 2nd floor location), the Polyphasers should be 
next to the equipment, not down on the ground. K4FMX hit the nail on the 
head on this topic, when he observed that grounding or shorting the coax 
at one point does not make the voltage to ground zero at other points 
along the coax, because the coax is both a transmission line in 
differential mode, and an antenna in common mode.

> If that boundary is extended by a conductive conduit from the shack out to the base of the tower or even to the top of the tower then they could be placed at those points.

Not true -- that conductive conduit is also an antenna, and there can be 
the same variation in voltage across it.

73, Jim K9YC