[TowerTalk] CATV & Phone grounds

[Jim Brown]

On Tue, 11 Jul 2006 10:49:32 -0700, Jim Lux wrote:

>How to tie really depends on why you're tying. 

Yes. If you think of lightning as DC, you're likely to be in 
serious trouble. IEEE studies show that the energy content in 
lightning has a broad peak around 1 MHz, with significant 
content well above and below that range. 

This means that the most important consideration is the 
INDUCTANCE of the network of conductors that tie to each other 
and complete the path to earth. 

To answer the original question -- YES, all of these "grounds" 
should be tied together by paths having the lowest possible 
inductance. That means SHORT conductors, and WIDE conductors. 
As others have noted, braid and stranded wiring is bad because 
it corrodes much more quickly than a solid conductor. That's 
why wide copper strap is preferred for RF bonding.

Ideally, from a lightning protection point of view, telco, 
CATV, power, and our ham antennas should all enter the premises 
at the same point so that the bond between them can be very 
short. 

In the real world, that doesn't always happen, and the bond 
between them may need to either run through the footprint of 
the house to be short, or must run around the perimeter. That's 
another argument in favor of multiple ground electrodes (rods) 
around the perimeter of the building, all tied together in a 
ring. 

It's also important to realize that Standards and Building 
Codes are influenced by political and financial interests (like 
power companies, telephone companies, and CATV companies). 
That's why the requirements for bonding of telco and CATV 
wiring are so lightweight.  

73,

Jim Brown K9YC
http:audiosystemsgroup.com