[TowerTalk] Back of desk grounding buss

[K4SAV]

On 3/22/2014 5:16 PM, Jim Lux wrote:
>
> I think we sometimes spend too much time worrying about lightning 
> safety, and not enough about power line safety. I've seen ham shacks 
> with all kinds of transient suppression on the coax, and automatic 
> grounding relays for coax, and all manner of stuff.  But if there were 
> to be a medium voltage to low voltage short on a neighborhood 
> distribution transformer, the shack would essentially be destroyed.  
> How much of your gear can take a 10-16kV overvoltage on the power cord?
> I've had first hand experience of the latter kind of overvoltage 
> twice! with substantial damage to appliances and wiring in both 
> cases.  Once was an underground transformer with an internal fault, 
> once was a wind induced failure of a MV feeder falling across the drop 
> to the house. (I'm also lucky to live in southern California, where 
> lightning is rare.  Those of you in Orlando probably have a different 
> take on things <grin>.  )


Yep.  Lived there 38 years and saw a lot of lightning damage.  Every 
house on my block had damage at one time or another.  A couple had holes 
blown in the roof.  Antennas stood no chance at all if the grounding was 
poor.  You guys in California live in a different world.

Even now living in an area (north Alabama) that generally has a lot less 
lightning, my little 70 (to top) tower takes a direct hit 2 to 3 time 
per year.  The problem is that I live on a small barren hill and my 
tower is the tallest thing around for a long distance.  Without good 
grounding, my house insurance would have been canceled in the first 2 or 
3 months.  I have yet to have any damage due to lightning, with many 
strikes.

What we really need in the area of lightning protection is education.  
On radio forums lightning protection is a very common question, usually 
more than one question per week.  When you look at all the answers, 
about 90% of them are wrong.  There are always "elmers" who are willing 
to recommend things when they don't have a clue as to what works.  Most 
of them recommend whatever they have and they have had no problems since 
they have never had a strike.  How is a noobe going to know what is 
right and what is wrong.

Even some of the better lightning books have serious errors.  I have sat 
thru several hamfest forums on lightning protection and listened to the 
presenters quoting errors from those books as facts.  A little education 
and common sense should have prevented this.

Even this forum isn't very good.  The obsession about back-of-the-desk 
bus bar is something that makes little difference for lightning 
protection.  When you are putting in large conductors at your desk to 
handle lightning currents, you have already lost the battle.  Large 
lightning currents inside your house is a recipe for disaster.  Proper 
grounding will keep all those high currents outside so you don't need 
big wires at the desk.  If you want a redundant ground at your desk for 
personnel protection against AC faults that's OK, but it's going to do 
nothing for lightning protection.

Jerry, K4SAV