Jim, the PDF you attached has a huge amount of information thank you. However what I see is pages of illustrations of ground loops and how to short them out with big bonding straps. Does this prove they don't exist? For me it highlights them. Perhaps I missed something important in the language?
When utilities provide power to domestic premises their only concern is profit whilst complying with local safety regulations. They don't give a hoot for EMI or lightning protection. This is in contrast to the good engineering practice universally employed in professional equipment installations where all factors are taken into account and bonding reigns supreme. Giving blanket advice to retrospectively interfere with domestic AC wiring and grounding IS risky unless you are completely appraised of all the relevant regulations and codes of practice that apply in every country and locality where people may be reading your advice. You also need to be aware of the requirements for certification in every country and locality that are needed to perform such modifications legally. Jim, I thought your blanket ground bonding ideas in a domestic situation were unwise. The advice given in the PDF on “Home Power Wiring, the green wire” is clearly wrong and can be outright dangerous. Why? I checked my house wiring. All of the ground wires (green wires) in my house lead back to the switch/fuse/breaker panel where they connect to the primary safety device, a ground leakage circuit breaker, the other side of which goes to a PME bonded “ground” connection. The bonding recommended in the PDF (house ground to a "real" ground rod) bypasses this circuit breaker, rendering it inoperative and leaving the building occupants vulnerable to lethal electric shock. The advice is written and in the UK would render you liable to litigation in the event of an accident. That is why I say it is unwise. In a professional installation the requirements for electrical safety, EMI, efficient RF grounding and lightning protection do not conflict. In a domestic situation they do. There may be no blanket solutions that apply everywhere, in all circumstances, in the domestic environment. This is not about good engineering practice, it is about how to work within electrical safety regulations and get as close as possible to what is needed in a good ham station. My friend would turn up at locations all around the world, sometimes only minutes before a broadcast, armed with a battery of equipment designed to combat the hum and noise inducing ground loops he would surely encounter, without the luxury of time to re-engineer all the wiring in the vicinity. Claude, I completely agree, a desktop will be much quieter at audio and RF and of course has a very obvious ground. The setup I describe had to be airline transportable for operating as VK2/G3NJV so I must use the (Lenovo) laptop. This has neither an internal chassis or a “D” connector. The only “grounded” metalwork visible are the HDMI and USB sockets, neither of which are accessible for bonding and which, upon inspection, connect to exactly the same internal PCB ground plane as the ground in the audio socket. Bond to a USB shell or the audio pin? Difference? Three inch wide copper strip to a USB or headphone on a laptop? Let's get real. Let us not lose sight of the point of this discussion which is to try to transmit a nice clean signal without added hum and noise. In my case there was a simple solution to the problem I unexpectedly encountered with the isolated cable which was to link the gound from laptop to rig. Spectrum analyser software run on the computer can check for hum and noise on receive, asking a local ham to listen to your transmission is good on transmit. One last point, how many people remember to disable their microphone when the PC is plugged to the accessory socket running WSJT-X? Listening in the FT8 band, clearly lots of people don't. Best regards Paul G3NJV ________________________________ From: Jim Brown <[email protected]> Sent: 11 August 2019 08:43 To: [email protected] <[email protected]> Subject: Re: [wsjt-devel] 60 Hz + harmonics sidebands on FT8 signals? (Paul Kube) On 8/10/2019 6:09 PM, Paul Randall wrote: > Jim > > Double insulated equipment like a laptop charger doesn’t have any > physical access to a metal part that can be bonded to ground. That’s > what double insulated means. Even if the charger has a 3 pin (hot, > neutral and ground) AC connector there is little likelihood that the dc > output side is connected to the ground pin. That does not change the fact that chassis-to-chassis bonding is good engineering practice, and audio interconnects should never be depended on for bonding. One of the reasons that proper bonding is critical to solve RFI and hum/buzz issies is the Pin One Problem. See my website for a lot of detail on that, and point your broadcast engineer friend to that, and to AES48. In this case using the > laptop for WSJT relies on the connecting wire running from the laptop to > the rig to provide a ground. If that wire is deliberately built to be > isolated then it CAUSES a hum problem rather than avoids one. This is > counter-intuitive and so even though it has nothing to do with software > development, I felt it was worth contributing to the “bad signal” > discussion going on in this forum. > > As an aside, I think it very unwise to make a blanket statement that > bonding everything together is good engineering practice. Sorry, that is a fact. Someone > reading that may unwittingly bypass a safety ground leakage circuit > breaker by bonding the building’s safety ground to a radio antenna > ground rod. Worse, large AC currents may flow in this connection if the > power utility company uses one of a number of different PME (protective > multiple earth) supply systems where the building’s safety ground is > actually bonded to the neutral supply wire and only to “real” ground > back at the supply transformer. I suggest that you study the tutorial on grounding and bonding in the link I posted. And if that isn't sufficient, buy N0AX's recent ARRL book on Grounding and Bonding, which is largely based on by work, and which cites the link I posted to it. > > Finally, my friend gave a big grin when he read that “The concept of a > so-called "ground loop" is completely false”. He is a professional sound > and television broadcast engineer. I am a retired audio and broadcast professional, vice-chair of the EMC Working Group of the Audio Engineering Society Standards Committee, principal author of all AES Standards on EMC, and a Fellow of the AES. My first job in Broadcasting was in 1959. Your broadcast colleague might also want to look at the White Paper on the topic I was commissioned to write on the topic, as well as the slides for talks I was hired to give to audio and video contractors and national conventions. They are in the pro audio section of my website. There are, indeed, differences in the way power is distributed around the world, and the White Paper addresses those differences. "Ground Loops" are a fiction that lead us to wrong solutions to real problems. Bill Whitlock (also a Fellow of the AES, and with strong RF chops) correctly identified the real issues, and my advice is based on his model. I suggest that you study my tutorial material. 73, Jim K9YC > > Cheers Paul G3NJV > > Sent from Mail <https://go.microsoft.com/fwlink/?LinkId=550986> for > Windows 10 > > *From: *Jim Brown <mailto:[email protected]> > *Sent: *08 August 2019 19:20 > *To: *[email protected] > <mailto:[email protected]> > *Subject: *Re: [wsjt-devel] 60 Hz + harmonics sidebands on FT8 signals? > (Paul Kube) > > The concept of a so-called "ground loop" is completely false. It has no > basis in physics. The "buzz" we hear when equipment is not properly > bonded consists of triplen harmonics of the mains frequency, 50 or 60 > Hz, depending on where you live. What DOES couple this trash is the > failure to follow proper engineering practice, which is to bond together > the chassis of every piece of equipment in a system, to bond all grounds > in a building, and to bond that combination of equipment to the > combination of building grounds. (my friends in the UK substitute the > word "earth" for "ground.") A second important part of good practice is > to get power for all interconnected equipment from mains (power) outlets > that have the same Green Wire (protected earth conductor), or whose > green wires are bonded together. > > When all of this done, the station is safe for lightning, and no > "isolation" is needed. > > Details of proper practice is at http://k9yc.com/GroundingAndAudio.pdf > > 73, Jim K9YC > > On 8/8/2019 3:43 AM, Paul Randall wrote: > > The point of the isolated interface is to prevent noise/hum caused by > > ground loops but if there is no ground at all, it is not only useless > > but actually causes a big problem. I can only assume that if I saw lots > > of 50Hz spurs on receive, there was a good chance they were there on > > transmit as well. > > > > _______________________________________________ > wsjt-devel mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/wsjt-devel > > > > _______________________________________________ > wsjt-devel mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/wsjt-devel > _______________________________________________ wsjt-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/wsjt-devel
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