On Tue, 19 Jan 2010 18:27:27 -0800, "Jim Brown" <[email protected]> wrote:
Jim, Thanks for that explanation of grounding methods. I got at least one of them right; I have a 1/2 inch copper pipe that runs along the back of the operating table that all of the equipment on the desk is grounded to. 73, Tom, N5GE [email protected] K3 #806 with SUB RX, K3 #1055, PR6, XV144, XV432, KRC2, W1, 2 W2's and other small kits 1 K144XV on order http://www.n5ge.com http://www.swotrc.net >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:[email protected] > >This list hosted by: http://www.qsl.net >Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
