Dear Don, This leaves me a bit concerned. I am planning to put up a K9AY receiving antenna in my backyard and it is supposed to be connected to a ground rod. I had never seen it suggested that this must be connected to the utility ground stake. I'm not even sure where the utility ground stake is. I've never noticed one though I will ask my electrician. If there is one, it is likely to be pretty far from the K9AY.
73, Dick, KA1SA At 10:22 PM 1/20/2010, Don Wilhelm wrote: >Joe, > >That is *one* reason *any* ground rod should be tied back to the utility >ground stake. It is as requirement of NEC, and should not be ignored. >If you drive ground rods for the ham station, connect those ground rods >to the utility entrance ground rod - no exceptions. The ideal is #6 or >larger wire, but if you cannot do that use whatever wire you can. Your >safety depends on it. If you cannot connect extra ground rods to the AC >mains entry ground, then do not drive those extra ground rods - they are >*not* an RF ground (see my many posts in the archives on that topic) - >and as Joe points out, in the event of a lightning strike (or equipment >fault), they may create a dangerous condition. > >You have 3 "grounds" to consider in the hamshack - 1) The AC safety >ground, 2) The lightning path ground, and 3) The RF ground. >1) and 2) may be one and the same, but 3) is a "horse of a different >color", and has nothing to do with a "mother earth" ground - it is a >point of low impedance at the frequency of interest, and usually exists >at some point in the antenna system, quite apart from "mother earth". >The English folks have the language a bit better and refer to "earthing" >which is often apart from "grounding", but we here in the US use the >same term for all common connections and in the process create confusion >for ourselves. > >73, >Don W3FPR > >Joe Subich, W4TV wrote: > > This creates a situation that is potentially hazardous > > to your equipment. The AC "third (green) wire" is supposed > > to be connected to ground only at the main panel/service > > entrance. However, since it is connected to the chassis > > of the power supply, it is also connected through the power > > supply and radio to ground via the coaxial cable. > > > > If the point at which the coaxial cables enter the building > > is not the same place that power enters the building, any > > nearby lightning strike can set up a significant difference > > in voltage between the power line "safety ground" and the > > RF ground (feedline shields/tower). That difference can > > fry any electronics connected to both "grounds." > > > > There are techniques for dealing with this problem ... but > > they are not necessarily easy or inexpensive. > > > > 73, > > > > ... Joe, W4TV > > > > > > > > > > > > > >> -----Original Message----- > >> From: elecraft-boun...@mailman.qth.net > >> [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Don Wilhelm > >> Sent: Wednesday, January 20, 2010 8:01 PM > >> To: David Woolley (E.L) > >> Cc: Rich; elecraft@mailman.qth.net > >> Subject: Re: [Elecraft] Grounding negative side of power supply? > >> > >> > >> The AC side should always be connected to the power supply chassis - > >> unless it is of the "double insulated" design where no ungrounded > >> metallic part can come into contact with the human body. > >> Yes, cutting > >> the AC "green wire ground" is a dangerous thing indeed - the entire > >> chassis could rise to the AC mains voltage in the event of a fault. > >> > >> The power supply negative *can* certainly be floating *if* > >> the designer > >> made provisions for doing that. It requires that all the common > >> connections on the secondary side of the transformer are > >> isolated from > >> ground. As I recall, Astrons are not built that way. > >> > >> 73, > >> Don W3FPR > >> > >> David Woolley (E.L) wrote: > >> > >>> Rich wrote: > >>> > >>> > >>>> I had a situation with an older (analog) power supply > >>>> > >> (that had its > >> > >>>> negative side grounded to the main AC ground) that tripped > >>>> > >> the Ground > >> > >>>> Fault Circuit Interrupter (GFCI) in one of the bathrooms. > >>>> Eliminating the bond to ground > >>>> > >>>> > >>> I consider this dangerous advice. If you have an ELCB > >>> > >> tripping, you > >> > >>> do > >>> not treat the problem symptomatically, by creating an > >>> > >> unsafer system, > >> > >>> you find out what the real problem is and you fix it. > >>> > >>> I can't tell what the exact wiring configuration is here, but it is > >>> very > >>> likely that you have created a situation where there are > >>> > >> pieces of metal > >> > >>> in reach which have low impedance paths to very different "earths". > >>> > >>> > >>> > >> ______________________________________________________________ > >> 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 > >> > > > > ______________________________________________________________ > > 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: 271.1.1/2634 - Release Date: > 01/20/10 04:12:00 > > > > >______________________________________________________________ >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 ================================================== Richard S. Lindzen Alfred P. Sloan Professor of Atmospheric Sciences Office: 54-1720, MIT Cambridge, MA 02139 USA 1 (617) 253-2432 (voice) 1 (617) 253-6208 (fax) Temporary Home: 100 Memorial Drive Apt. 2-2a Cambridge, MA 02142 USA 1 (617) 945-5784 (voice) ================================================== ______________________________________________________________ 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
