For some reason, they're not to be found in the Engineering department.More seriously, the old cold-water pipe myth seems to be resurfacing. It just won't die.
Long ago, when the world was young, cities used metal pipes to distribute water, so the average cold-water pipe probably was a fair ground. And at that time, there was no safety ground, just hot and neutral, so the cold-water pipe was likely the best ground available.
But any installation done in the last 40 years or so probably uses plastic underground. Even if the internal piping is copper, this stops six inches outside the basement wall, and it's plastic from there on out.
If things have been done correctly, the pipes are in fact grounded, but only because there's a wire connecting them back to the electrical panel. This is required by electrical codes, so that the plumbing can't become "hot" due to leakage or accidental connections (BTW, it's a good idea to check that this is present, and that plastic items like water softeners are properly bypassed).
73 Bob Bill Carns wrote:
John, This is a common set-up and always causes varying degrees of grief.As a practicing RF engineer for many years, I will tell you the following.There is no such thing as ground. There are wires run to a point called ground by different entities that are at different DC, AC and RF potentials depending on location, use and condition. The wire you run from the 30S-1 to the AC mains plug, as well as the "ground wire" running in the wall to the AC breaker box, where neutral and "ground" are common, has electrical "RF" length and distributed inductance, making it a fine radiator at times, especially if you are a long run from the box or on the second floor.For safety, there should be a second AC "code" ground going to your 30S-1. I use one on mine and tie it to the chassis/case. But, realize that the RF cable that is tied to the case at the exit "grounded there" is also probably tied to some other "RF" ground at the other end - like at a beam. You can easily wind up with RF ground loops as well as floating RF potentials on what you think is "ground" - like getting an RF burn off your mic.There are some good "Rules of thumb" regarding grounding.On balanced antennas, like a beam or a dipole, use a balun to keep as much RF as possible off the shield.In addition to the balun, I like to try and get a 10 turn "choke" wound out of the incoming feed line as close to the antenna as possible. Bundle it tight.Keep as much of your primary code ground as big a wire a possible to minimize inductance. 3 inch up to 12 inch flat copper strap works the best. If you have this type of floor or wall mounted ground routed, then you can skip the ground safety wire as long as the strap goes back to the neutral common point.Keep your grounds as short as possible, and when running feed lines, try and keep them below ground.Map your ground system including house and shop or shack and really try and make sure there are no ground loops that can radiate RF.I have tried to stay away from the controversial subjects like multiple ground points and lightning protection. There has been much written here in the past about this and so do not want to stir up a big re-thread of that subject. Hopefully the reflector archives will be back on line soon and you can go there for that kind of help.Now, all that being said, RF ground protection is a tricky subject and in the long run you have to do it the best you know how to start with and then tweak it if you get problems.Hope this helps, Bill Carns, N7OTQ K0CXX, Trustee MRCCC Editor Signal Magazine CCA # 94-00009 Wimberley, Texas 512 847 7010 ----- Original Message ----- From: "John Cox" <jecox@xxxxxxxxxxxxx>To: <entropycat@xxxxxxxxxxx>; <vlecken@xxxxxxxxxxx>; <collins@xxxxxxxxxxxxx>Sent: Tuesday, April 22, 2008 6:57 PM Subject: {Collins} Re: 30S-1 question for ground connection for 230VACI am getting ready to bring my 30S-1 up and after reading about all of the ground loop problems ran a 4 wire service to my new shack and will run all of my grounds back to the main panel through the 4 wire ground. I was thinking that I can use the existing 110 volt 30S-1 cable for the 220 and neutral and run a separate ground wire from the outlet to the 30S-1 ground point and run all of the other equipment grounds to this point. my ground and neutral are common at the main panel so the ground on the 3 wire 110 is also neutral. Is this going to cause a problem rf wise?Thanks in advance for your comments. 73, John kc0yai ----- Original Message ----- From: <entropycat@xxxxxxxxxxx> To: <vlecken@xxxxxxxxxxx>; <collins@xxxxxxxxxxxxx> Sent: Tuesday, April 22, 2008 5:38 PM Subject: {Collins} Re: 30S-1 question for ground connection for 230VACHi Luc!If you look at the schematic for the 30S-1, you will observe that onlythe plate transformer has dual primary windings. The remainingtransformers (bias supply, rectifier filaments and 4CX1000 filaments) all have single primaries and are intended to run on 115 volts. Here in theUnited States, the center tap of the 230 volt mains supply is called a"neutral". It is necessary to bring this neutral into the 30S-1 in orderto provide the 115 volts required for the small transformers.Also, here in the United States, it is a violation of the electrical code to tie the neutral and ground together at any point other than at the mainservice entrance to the building.I would suggest that you provide a separate ground to the 30S-1 chassis, and do not connect it to the neutral line (terminal 2 of TB201) in any way.Regards, Jim T. KB6GM entropycat@xxxxxxxxxxx ----- Original Message ----- From: "Luc Vlecken" <vlecken@xxxxxxxxxxx> To: <collins@xxxxxxxxxxxxx> Sent: Tuesday, April 22, 2008 9:51 Subject: {Collins} 30S-1 question for ground connection for 230VAC Hello to the list,Can somebody explain me please the connection for the mains power to the30S-1.(for 230V that is) I have a 30S-1 winged emblem now and the ground of the mains in now connected to connector 2 only.There is no ground connection made to the side (or chassis) via the mainscable. Do I have to leave it this way?Why is that ground not connected to the chassis but to connector 2 (middleof the mains transformer)? Thanks for any clarification. Kind regards, ON4ALV mailto:vlecken@xxxxxxxxxxx _________________________________________________________________ Even niet achter je PC? Neem je Messenger mee op je gsm! http://www.windowslivemobile.msn.com/nl-be . SHARE THE FUN: JOIN THE COLLINS COLLECTORS ASSOCIATION TODAY ! http://www.collinsradio.org/membership/ -paypal accepted- . NETS: Tues & Thur: 3.805 MHz-2000 Central + Fri: 3.895 MHz-2000 Pacific SUNDAYS: 14.263 MHz-2000 UTC + AM Net: 29.050 MHz-1200 Central 1st Wednesday AM Net 3.880 MHz-2000 local (ET, CT, MT, PT). SHARE THE FUN: JOIN THE COLLINS COLLECTORS ASSOCIATION TODAY ! http://www.collinsradio.org/membership/ -paypal accepted- . 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