|Subject:||Re: NASA and braid was Re: [TowerTalk] There's 'ground', andthen there's 'ground'|
|From:||Jim W7RY <email@example.com>|
|Date:||Sun, 16 Jan 2005 21:28:08 -0800|
At Motorola the "R56 Site Standards and Guidelines for Communications
Sites" strictly prohibits braid of any kind on a communications site.
Mostly because of the noise it generates when it gets old and deteriorates.|
The underground conductor interconnecting all of the ground rods is #2 AWG tined solid copper. This conductor is also attatched to the MGB (Master Ground Bar) inside of the building just below the cable entrance window. There is also a EGB (External Ground Bar) on the exterior of the building. The exterior bar is where the coax shields are grounding before they enter the building.
The MGB is where the lightning surge suppressors are mounted or connected directly to. (Within 18 inches using #6 AWG minumum).
Each equipment rack has a RGB (Rack Ground Bar). Each piece of equipment in each rack is bonded to this bar. Each RGB is bonded back to the MGB with stranded jacketed #2 AWG wire in a single point ground fashion.
The AC power grounding conductor is also connected with a #2 AWG conductor to the MGB.
The MGB is the single point ground location.
It's not rocket science... Heh Heh.....
BTW the Motorola R56 is based on the following INDUSTRY STANDARD DOCUMENTS:
NEC, The National Electric Code.
TIA J-STD-607-A (This is the best document to refer to)
ANSI T1.333 and T1.403
As for NASA, I don't have their document or documents.
When you have fully read the above documents and understand their content and proper application techniques........ You will know.....
At 08:30 PM 1/16/2005, Jim Lux wrote:
> > Many construction standards prohibit braided straps in RF or > lightning paths unless the connection absolutely must have > braiding in order to withstand flexing, and then the braid > is often substantially oversized to make up for its reduced > current capacity. It's my understanding NASA restricts use > of braiding, and I can cite many cases where braiding will > either cause excessive loss or actually fail in high current > RF systems.
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
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