[TowerTalk] There's 'ground', and then there's 'ground'

Sun Jan 16 15:50:29 EST 2005

In my former existence as a Rocket Engineer, I worked on a 1000 acre plant 
site that had many buildings all with lightning protection per MIL spec 
(Ordnance corp) In 38 years, the only lightning damage was when a Lab was 
hit. Investigation showed that the ground connection had been cut by a 
painting contractor. All the buildings had "lightning rods" connected to a 
trenched copper braided network. The braided wire was large ( I never 
measured it) and was of a complex woven braid. All bends were with large 
radii.  Even the covered walkways (often several hundred feet) between 
buildings were "protected".
It worked for us.
Bill

At 12:25 PM 1/16/2005 -0500, Pete Smith wrote:

>Fascinating, Frank.  I tried going back up the URL tree, and eventually 
>found myself at a page for Presbyterian gun owners!  However, beginning at 
>least with /ground2.htm there's a  lot of good stuff there.
>
>The quoted info puzzles me, though -- my old farmhouse has lightning rods, 
>and the cable between them and from them to the ground rods placed at 
>intervals around the house is roughly 3/4 inch diameter aluminum, made 
>from many ~#14 strands that are braided in a fairly complex pattern.  It 
>is quite flexible and easy to work with.
>
>When I went looking for home lightning rod suppliers on the Internet, it 
>appeared that all vendors for this kind of service are still selling this 
>braided aluminum stuff, and only this.
>
>I guess I'm perplexed -- if it doesn't conduct lightning well, how can 
>these people continue to sell it and stay in business?  I'd think their 
>liability headaches would be phenomenal.
>
>73, Pete N4ZR
>
>At 10:50 AM 1/16/2005, Frank Donovan wrote:
>
>>Hi Jim,
>>
>>Here's another one to add to your list:
>>
>>Discard all forms of "braided" cable. Braid is something a girl does to her
>>hair.
>>It is not a good RF ground and it's a terrible conductor for lightning
>>energy.
>>
>>Use braid only for DC and audio applications, its just an inductor
>>for RF or lightning protection applications
>>
>>Here's an excellent reference from the many industry sources on this topic:
>>http://members.cox.net/pc-usa/station/ground5.htm
>>
>>73!
>>Frank
>>W3LPL
>>donovanf at erols.com
>>
>>
>>
>>----- Original Message -----
>>From: Jim Jarvis <jimjarvis at comcast.net>
>>To: <towertalk at contesting.com>
>>Sent: Sunday, January 16, 2005 6:56 AM
>>Subject: [TowerTalk] There's 'ground', and then there's 'ground'
>>
>>
>> >
>> > 1)  I think you'll find that all unibody constructed cars
>> > have serious anti-corrosion coatings applied, after welding.
>> > Bolted-on components are almost never electrically connected,
>> > unless there is a reason for it, as it represents both extra
>> > work, and a breach of the corrosion protection.
>> >     As the owner of two Passat's which had an ic706-2 installed,
>> > I was careful to attach to the unibody when installing the
>> > antenna.  Cutting holes is painful, though...as was the bodyshop
>> > repair when I sold the vehicles.
>> >
>> > 2)  Most contemporary transceivers do not have a single point
>> > ground.  There is a logic ground, an RF ground, an audio
>> > ground, and a chassis ground.  They exist in different areas of
>> > the radio, on different boards, and may be deliberately
>> > separated from the chassis, for purposes of noise reduction.
>> >     Yes, chassis ground shows up on the back panel.  And yes,
>> > I would expect RF ground shows up at that point, too.  But
>> > the logic and audio circuits reside internal.
>> >     I think you'll find the mic 'ground' isn't the cable shield.
>> > You'll also find that the 'shield' side of the mic audio connects to
>> > chassis ground, on the PCB, via a resistor of 10 ohms or so.
>> > There is usually a 'single point ground' for audio, which references
>> > that circuit to chassis, and prevents ground loops. The mic element
>> > itself is usually floating within the housing.
>> >
>> > 3) External audio processing equipment requires particular care
>> > not to create ground loops.  As someone observed, pro-audio folks
>> > put real effort into that, in their equipment.
>> >
>> > 4) One could write a volume on proper grounding and shielding in
>> > the mixed signal environment presented by a hamshack.  And I won't.
>> > At least not here.  Just one sentence:
>> >
>> > SAFETY GROUND SHOULD BE TESTED.  SPEND 10 BUCKS ON A 'PLUG CHECKER',
>> > AND TEST ALL OUTLETS THROUGHOUT YOUR HOME.  YOU MAY BE SURPRISED,
>> > PARTICULARLY IF YOUR HOME WAS BUILT IN THE 60'S, OR HAS ALUMINUM WIRING.
>> >
>> >
>> > n2ea
>> > jimjarvis at ieee.org
>> >
>> > _______________________________________________
>> >
>> > 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.
>> >
>> > _______________________________________________
>> > TowerTalk mailing list
>> > TowerTalk at contesting.com
>> > http://lists.contesting.com/mailman/listinfo/towertalk
>>
>>_______________________________________________
>>
>>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.
>>
>>_______________________________________________
>>TowerTalk mailing list
>>TowerTalk at contesting.com
>>http://lists.contesting.com/mailman/listinfo/towertalk
>
>_______________________________________________
>
>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.
>
>_______________________________________________
>TowerTalk mailing list
>TowerTalk at contesting.com
>http://lists.contesting.com/mailman/listinfo/towertalk
>

Bill Aycock - W4BSG
Woodville, Alabama 