First, I recommend the following:
http://www.arrl.org/shop/Grounding-and-Bonding-for-the-Radio-Amateur/
well worth the price.
second, bleeding off does not prevent discharge. Many such systems are
garbage or worse. "bleeding off" is corona discharge from sharp points
submitted to a large electric field, such as under or near a
thunderstorm. It's gonna happen.
I think what's meant here by a halo system is a conductor dug in to a
shallow trench? If so, Scott is correct.
next, most of the time, damage is done by induced currents rather than
direct hit by the stroke terminus. These can be eased by proper power
treatment and good single point grounds. I personally do not trust MOV
ground protectors. They are only good for a certain, unknown, number of
hits, and are useless after that. There is no way to tell if the limit
has been reached. Surge protection on AC power needs doing only at the
main breaker box from each side of the 220 to ground.
and, if you are on a tower and hear the sizzling noise of corona, get
down pronto.
Hope this helps.
Don
On 2018-06-19 12:55, Bob kb8tq wrote:
Hi
If indeed a proper ground system *could* be depended on to “bleed off”
and prevent discharge things
would be *much* simpler. Indeed I’ve been on towers and decided to
exit that location as the bleed
process became audible. It very much does happen. It simply is not a
100% sort of thing.
Bob
On Jun 19, 2018, at 12:01 PM, Scott McGrath <scmcgr...@gmail.com>
wrote:
Probably the easiest and most economical grounding system is the halo
ground with antenna grounds bonded to the halo and the house ground
bonded to the halo as well.
The halo conductor sizing is governed by local codes, But really
what you are doing ensuring that the entire structure and earth around
it is at the same potential so a nearby strike does not cause ground
currents to flow.
A direct strike is probably going to fry anything it hits because of
the gigajoules of energy concentrated within the discharge
But a proper ground system also ‘bleeds off’ the potential difference
thereby preventing discharge
Content by Scott
Typos by Siri
On Jun 19, 2018, at 11:19 AM, Bob kb8tq <kb...@n1k.org> wrote:
Hi
18” down in a swamp likely is plenty for conductivity. 18” down in a
sandy desert (or on an ice sheet) may be way
short in terms of conductivity :) The real answer to any of this is
“that depends”. (Yes, the ice sheet grounding
problem is from a real case that shows up in some class notes from way
back ….).
Some locations get multiple hits on a weekly basis in the summer.
Other locations get a close strike once every
few decades. What makes economic sense for one probably does not make
sense for the other…. A “full up”
protection setup can easily run into hundreds of thousands of dollars.
I’d much rather spend that kind of money
on a Maser … or two …. or three :) …. this is TimeNuts after all ….
Bob
On Jun 19, 2018, at 10:56 AM, Scott McGrath <scmcgr...@gmail.com>
wrote:
The 18” inch requirement is partially for damage resistance and
partially to ensure adequate soil moisture for conductivity.
Content by Scott
Typos by Siri
On Jun 19, 2018, at 10:50 AM, jimlux <jim...@earthlink.net> wrote:
On 6/18/18 6:39 PM, Glenn Little WB4UIV wrote:
To do the grounding correctly, all connections exterior to the
building are to be welded.
The cable to ground rod welds are to be 18 inches below grade.
The exterior cable is to be number 2 copper or larger.
To bond numerous ground systems together, a number 2 copper cable is
to be buried at 18 inches and welded to each ground system.
If using eight foot ground rods, a ground rod is to be driven every
16 feet along the connecting cable and the cable welded to the rod.
It helps to know *why* some requirements exist - I suspect the 18"
burial requirement is to avoid accidentally digging it up or damaging
it. I can't think of an electrical reason for it.
A lot of work, but, cheaper, in the long run, than continuing to
repair/replace equipment.
It depends
Unless you're doing geodetic or precision timing work with a 2 or 3
band GPS, replacement GPS antennas are cheap.
I'd worry about the receiver and related equipment, but the antenna
itself might be sacrificial.
As always, there's a risk/budget tradeoff
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