[TowerTalk] Ground...and talking around it

[Jim Jarvis]

Guys...

A few true-isms:

1) coax braid will not handle lightning currents. It will
evaporate before draining a strike.  Ground strap is better,
out of the box, but after corosion, and depending on how you
bend it...it may or may not work.

2)  Copper strap is the only answer.  And even then,  you need
to make sure you have gentle bends.... 18" radius is about right.
Else, you have an inductor.

3)  If your house/station ground does not have a single point
system...if telco or power come in elsewhere, and wander around
before reaching your RF ground.... you've got a lightning problem.  

In practice, and with older homes, this is hard to do.  Still, it's
real. Much easier to do with new-build.   

I did a single point ground at a radio studio for AM/FM/telco/power,
audio...5 control rooms and 4 studios/announce booths...the worst 
noise was a burble when the strobes on the 500' FM tower fired. 
And that was at -140dBm in the audio chain (vs. signal at -30dBm) 

Imagine, for a moment, that you might live on a sailboat for a while.
You may be the highest point for 30 miles.  How would you ground your
mast?  A #8 wire, as the manufacturer recommends?   Coax Braid, which may
corrode?  Or copper strap from mast to keel?  

You know where I come down.

n2ea
jimjarvis at ieee.org