Don Wilhelm wrote: > Jim (and all), > > I believe we are both correct - and "it all depends...". > The variety of "sneak" ground paths from one piece of equipment to > another are numerous indeed (pin 1 problems are another source of > trouble, and may confuse the real source as well). A star grounding > system is the first place to start (IMHO), but additional bonding may be > helpful in some situations. There is no one right answer - it all > depends on your particular installation and your antenna installation. > Is the problem RF or is it from ground current coupling from one piece > of equipment to another? How to treat a particular problem will depend > on the answer to that question. And, if it is caused by ground > currents, the method to properly reduce them will vary from one > installation to another (bonding the offending two pieces of equipment > by a low impedance path may be required). A good starting point is in > Jim Brown's website information, but the total answer is station to > station dependent - this is not a case where "one size fits all". Some > investigation along with a bit of trial and error may be required. > Consider that "sneak" grounding paths are just what that indicates - > they are unwanted and unlikely to be obvious to casual observations. > > 73, > Don W3FPR > > Jim Brown wrote: > >> On Tue, 19 Jan 2010 17:55:04 -0500, Don Wilhelm wrote: >> >> >> >>> I agree too, but would like to clarify that the "bonding" should not be >>> a "helter-skelter" connection of one piece of equipment to another. >>> The most effective way of accomplishing that is to connect each piece of >>> equipment in the shack to a common point (which may be optionally >>> grounded or connected to a low impedance for RF (mother earth ground is >>> only for lightning protection and personal safety, not RF grounding). >>> That type of bonding connection is often referred to as a "star" >>> configuration - as opposed to a 'daisy-chain' where the connection is >>> >>> >> >from one piece of equipment to another. >> >> There are really at least three different issues being addressed here. >> One of them is bonding for lightning protection and power system safety. >> The bonding that I was talking about to solve this issue is specifically >> aimed at solving what I suspect are pin 1 problems in the interconnected >> equipment. So the function of the bonding I recommended is to provide a >> low impedance path from chassis to chassis, so that RF is more likely to >> flow on the bonding conductors, chassis to chassis, than on interconnect >> cables (audio and control) into the circuit board and into the circuitry >> (by the pin 1 problem). That's also the reason for ferrite chokes on the >> interconnect cables. >> >> I certainly agree that a very low impedance bond of all equipment to a >> single point is a good idea. BUT -- I don't want the path from computer >> chassis to rig chassis to be any longer than necessary -- I don't want it >> to go to the center of the star and back, for example. I've seen this >> "star" approach implemented with a piece of copper pipe that runs along >> the back of a radio bench, with a dozen or so wires connected at points >> that are 6-10 ft apart. By contrast, my laptop sits on my operating bench >> between two K3s, and there's a short piece of #10 braid going to both >> rigs. The third reason for bonding is to minimize the audio voltage from >> chassis to chassis that is caused by leakage current in the power system, >> and that gets added to signal for any unbalanced connection between >> equipment. By bonding that equipment with big copper, we minimize that >> voltage (and divert the current away from pin 1 problems as well). >> >> As for my lightning protection bonding -- THAT'S where I implement the >> star. The rigs are bonded to the power outlet green wires with a short >> piece of braid (outlets are just below the bench). The power outlets are >> bonded to the coax entry panel, also just below the bench, which in turn >> goes to a half dozen ground rods. There's also a lot of coax routed >> through various switches to the coax entry panel (with feedthrough >> arrestors). That provides a DC bond, but those coaxes have a lot more >> inductance compared to the short braids. The power outlets run in EMT >> (thinwall steel conduit) back to the power panel, which has three ground >> rods of its own, on the other side of the small building that houses my >> shack, and some #4 copper runs around the perimeter of the shack to tie >> the ground rods together that way. >> >> Does this clarification allay your concerns? >> >> 73, >> >> Jim K9YC >> >> >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:Elecraft@mailman.qth.net >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> ------------------------------------------------------------------------ >> >> >> No virus found in this incoming message. >> Checked by AVG - www.avg.com >> Version: 9.0.730 / Virus Database: 270.14.150/2632 - Release Date: 01/19/10 >> 02:34:00 >> >> >> > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > ------------------------------------------------------------------------ > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 9.0.730 / Virus Database: 270.14.150/2632 - Release Date: 01/19/10 > 02:34:00 > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net
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