Ground is a Myth? - Page 1
Forum section: electronics / rf-microwave

author: mtwieg
author_rank: Frequent Contributor
timestamp: December 09, 2024, 02:26:00 pm
content: The true ground is.... in your heart.

author: coppice
author_rank: Super Contributor
timestamp: December 09, 2024, 02:49:23 pm
content: I know ground plane is not a myth. I had to fix the design of a control system for an aircraft, as it was causing a lot of vibration and wear and tear in a gear box. I can tell you there was a lot of ground plane when we opened up those gearboxes.

author: Sassy Taste
author_rank: Contributor
timestamp: February 27, 2025, 09:12:20 am
content: I was first taught in electrical the ground was the direction current will flow if it shorts circuit. Goes to the ground. In Electronics term the ground is the negative terminal of the battery or the metal chassis common ground location. Not a myth, but a conceptual idea.

author: wasedadoc
author_rank: Super Contributor
timestamp: February 27, 2025, 10:12:54 am
content: Quote from: Sassy Taste on February 27, 2025, 09:12:20 am1. Your teacher was incorrect about short circuit current direction.2. Negative is not guaranteed to be ground. For example, many vehicles had positive grounded battery (ie battery positive connected to chassis) in the past.3. Lots of equipment has no "ground" connection at all. Both positive and negative of the supply are floating with respect to actual ground. Common example is a mobile phone. Even when being charged (with a wired charger) no part of the phone is grounded.

author: tggzzz
author_rank: Super Contributor
timestamp: February 27, 2025, 11:09:39 am
content: What is "ground" in a flying aircraft? Not understanding that used to cause aircraft to destroy themselves on the ground.If caught in an open field in a thunderstorm, you are advised to (1) crouch down (2) only feet (not hands) on ground (3) feet close together. Why (2) and (3)?

author: nctnico
author_rank: Super Contributor
timestamp: February 27, 2025, 01:06:58 pm
content: Quote from: tggzzz on February 27, 2025, 11:09:39 amThe currents can be high enough to cause a lethal voltage differential across the distance between your hands and feet. That is also why your feet should be close together. And your shoes provide some isolation.

author: tggzzz
author_rank: Super Contributor
timestamp: February 27, 2025, 01:19:49 pm
content: Quote from: nctnico on February 27, 2025, 01:06:58 pmYup.Ground != equipotential. So whatisground,if anything?Hint: "all models are wrong but some are useful". It is EM fields, all the way downThat's the bit that too many people don't understand.

author: CaptDon
author_rank: Super Contributor
timestamp: February 27, 2025, 02:16:08 pm
content: Feet close together VERY GOOD ADVICE!!! I was barefoot and putting my horses in the barn during a heavy thunderstorm. As I was guiding the last horse (she was a paint colored mare from Assateaque Island and used to standing under trees during rain) into her stall lightning struck at the corner of my paddock area onto a metal fence post. The current traveled through my legs and it felt like someone ripped my hamstrings right out of my legs!!! Fortunately it had no effect on my heart or anything other than leg muscles. For several days my legs hurt as if I had run 50KM full speed non-stop. The mare's rear end got jolted also! I will never forget the look she gave me!!! I believe she thought I did it to her!!!

author: radiolistener
author_rank: Super Contributor
timestamp: February 28, 2025, 02:18:28 am
content: Quote from: tggzzz on February 27, 2025, 11:09:39 amIn a flying airplane, the ground is the metal chassis and metal body of the airplane.While an antenna is a radiator placed outside the aircraft ground (metal body). Both - radiator and ground are working together as antenna system. When an airplane is on the ground, you can think of the Earth's surface as a mirror reflecting radiation from the airplane's antenna system. Just like a wall acts as a mirror for the light of a flashlight.

author: nimish
author_rank: Regular Contributor
timestamp: February 28, 2025, 03:02:06 am
content: Among the ways gauge freedom in the electromagnetic field manifests is the ability to call any particular voltage "0V" or "ground" or "reference" or "chassis" and it's all the same as long as you're consistentThis is the consequence of the conservative nature of the field.Quote from: tggzzz on February 27, 2025, 01:19:49 pmAs you say this is a breakdown of the model where we typically assume that the literal ground is a perfect conductor and is therefore taken to be at equipotential. Of course this is false, and the impedance of the soil and such is relevant, but that's being pedantic; in a typical circuit "ground" is _assumed_ to be at equipotential.If you really want to be precise then nothing is at equipotential since there's no such thing as a perfect conductor (even a superconductor isn't one all the time).

author: themadhippy
author_rank: Super Contributor
timestamp: February 28, 2025, 03:18:10 am
content: but equipotential maybe not ground,2 points on a circuit can be at equipotential to each other,but with a potenial difference between them and ground

author: tggzzz
author_rank: Super Contributor
timestamp: February 28, 2025, 09:35:20 am
content: Quote from: radiolistener on February 28, 2025, 02:18:28 amThat is "ground" as much as this is "ground".

author: coppercone2
author_rank: Super Contributor
timestamp: March 01, 2025, 08:59:24 am
content: ground problems

author: voltsandjolts
author_rank: Unknown
timestamp: March 01, 2025, 09:15:48 am
content: Do aircraft have ESD tyres?

author: coppercone2
author_rank: Super Contributor
timestamp: March 01, 2025, 09:28:44 am
content: https://monroeaerospace.com/blog/why-airplane-tires-are-made-of-conductive-rubber/I think they should throw out a copper anchor out of the window while landing thoughhttps://www.facebook.com/DeptofDefense/videos/helicopter-support-team-exercise/347065752729495/"static man"

author: SiliconWizard
author_rank: Super Contributor
timestamp: March 05, 2025, 08:21:50 am
content: Quote from: mtwieg on December 09, 2024, 02:26:00 pmPossibly, but you may not want to stick a pole into it.

author: A.Z.
author_rank: Super Contributor
timestamp: March 05, 2025, 08:49:12 am
content: Quote from: SiliconWizard on March 05, 2025, 08:21:50 amin particular in case one is a vampire

author: mtwieg
author_rank: Frequent Contributor
timestamp: March 05, 2025, 12:22:19 pm
content: Maybe the real ground was the friends we made along the way.

author: jonpaul
author_rank: Super Contributor
timestamp: March 05, 2025, 12:53:53 pm
content: "There are NO grounds , just paths to return curretns"- My old friend and mentor Dick SEQUERRA (exMarantz, Sequerra Co.) 1971EVERY path to return of power supply, or safety (earth) ground has an impedance which varies with frequency.Most significant in high current, high power, RF anf microwave, as well as high resolution analog,Have a great dayJon

author: TimFox
author_rank: Super Contributor
timestamp: March 05, 2025, 01:01:04 pm
content: Before I retired, I called it “the g word” (NSFW), and insisted on using exact terms such as “safety ground”, “signal low”, “chassis”, or “power supply return”, which were relevant.

author: Nominal Animal
author_rank: Super Contributor
timestamp: March 05, 2025, 03:10:33 pm
content: Ground? I don't even have mains "Live" and "Neutral".We have CEE 7/3 unpolarized wall sockets. Most households get three-phase 400 VAC power, and often the 240 VAC mains is just two legs off the three-phase power. There often are three different "phases" of wall mains sockets, depending on the circuit and the phase pair.Now, throw in your typical wall warts and un-grounded isolated supplies, that assume they get "live" and "neutral", and reduce EM noise by coupling the output DC "GND" (0V reference) to the "neutral".Try to connect two such devices that happen to be powered from different outlets in different circuits and different pair of three-phase power, or one such device and one that uses a proper "grounded" power supply, and you find that the two DC "GNDs" do not agree at all, with some hundred volt oscillating difference.Then, when I describe here how I use digital isolators (mostly TI capacitive ISO67nmand ISO77nm) to deal with this, I get ridiculed as a drooling idiot using isolators where none are needed, as the "proper" solution is to use proper grounded lab supplies everywhere. (I mean, Iama drooling idiot, my pillowcases being proof of that; but not because of the isolators, which are just a cheap, practical solution to a technical problem.)Thus, I consider "GND" just a placeholder for "zero-volt reference potential", and the ground potential available on those CEE 7/3 sockets being "actual ground". On cables and devices, there is "chassis ground", and possibly "safety ground". And whenever someone discusses mains circuits using "live" and "neutral", I get a bit frustrated.

author: TimFox
author_rank: Super Contributor
timestamp: March 05, 2025, 03:21:04 pm
content: For US single-phase 3 prong outlets, my terms are “line”, “neutral”, and “safety ground”, which are black, white, and green, respectively.Of course, the European color code is different: brown, blue, and yellow-green.Since the color codes are independent, one often sees the European colors in the US.

author: tooki
author_rank: Super Contributor
timestamp: March 05, 2025, 06:30:53 pm
content: Quote from: TimFox on March 05, 2025, 03:21:04 pmIt's not a "European color code": Europe simply uses the IEC standard (60446) used by most of the world.

author: TimFox
author_rank: Super Contributor
timestamp: March 05, 2025, 06:46:52 pm
content: Quote from: tooki on March 05, 2025, 06:30:53 pmReworded: The color code used in Europe.As I understand it, there are obsolete color codes once used in some parts of Europe where PE (“ground”) was red.Yes, that IEC standard is widespread: I was making a statement of fact about the different code used in the US, along with the term “line” used for one of the three wires in US wiring.White is reserved for neutral and green (or green/yellow) reserved for ground, but line can be other colors than black (for three phase or switched wires).I agree about not using “live”: that is a status, not a label.

author: Zero999
author_rank: Super Contributor
timestamp: March 05, 2025, 09:26:55 pm
content: Quote from: coppercone2 on March 01, 2025, 09:28:44 amMost tyres are slightly conductive, including those on cars. They're loaded with carbon, which is why they're black. I have no idea of whether aircraft tyres are more conductive, than road tyres.

author: A.Z.
author_rank: Super Contributor
timestamp: March 06, 2025, 01:33:52 pm
content: a bit of warninghigh frequency (aka "RF") ground and low frequency one (the usual DC Ground) aren't made equaljust in casehttps://www.w8ji.com/ground_systems.htm

author: coppercone2
author_rank: Super Contributor
timestamp: March 07, 2025, 12:44:35 am
content: yes, because DC does not care about the pF of capacitance you have

author: A.Z.
author_rank: Super Contributor
timestamp: March 07, 2025, 08:26:46 am
content: Quote from: coppercone2 on March 07, 2025, 12:44:35 amok now think at AC mains do you see any difference between that and a ground used at (say) 3MHz ?

author: A.Z.
author_rank: Super Contributor
timestamp: March 07, 2025, 11:38:03 am
content: just as a notehttps://helpdesk.flexradio.com/hc/en-us/articles/204779159-Grounding-Systems-in-the-Ham-Shack-Paradigms-Facts-and-Fallacies

author: coppercone2
author_rank: Super Contributor
timestamp: March 07, 2025, 02:44:30 pm
content: I just mean that=for high frequencies there is often basically a short that is a open for low frequencies because of capacitance. I was thinking more like VHF vs DC.

author: cruff
author_rank: Regular Contributor
timestamp: June 28, 2025, 09:37:45 pm
content: Quote from: coppice on December 09, 2024, 02:49:23 pmCame to this thread late. My impression was that coppice was being mildly sarcastic about "ground (up) plane (gears)".