[time-nuts] GPS Antenna Grounding/Lightning protection.

[Scott McGrath]

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 <kb8tq at 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 <scmcgrath at 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 <jimlux at 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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