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

Bob kb8tq kb8tq at n1k.org
Tue Jun 19 11:19:41 EDT 2018


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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