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Astron PS and Your Ground

Discussion in 'General Technical Questions and Answers' started by AI5DH, Oct 29, 2019.

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  1. AI5DH

    AI5DH Ham Member QRZ Page

    To work around that problem bench technicians use an Isolation Transformer. A Medical grade unit by Tripp Lite 1500 KVA. You have to make one mod and lift the bonding jumper on the secondary. Here is a link to a decent video on it.
     
  2. KD0CAC

    KD0CAC Ham Member QRZ Page


    I did that , but have not used it with a O-scope yet , wanted 2nd , 3rd opinions / confirmations ;)
    Thanks will check that video .
    I have one of the Topaz isolation transformer , little confusing - tech vers. , medical vers. , public .

    Hay , he is waring one of Dave's shirts , Dave's EEVblog .
     
    Last edited: Oct 31, 2019
  3. K0OKS

    K0OKS Premium Subscriber QRZ Page

    Watch Dave Jones’ How not to blow up your oscilloscope video. But we should be careful that this thread ia getting hacked.

    Also, remember that a Variac is NOT isolated by itself.

     
  4. KD0CAC

    KD0CAC Ham Member QRZ Page

    Watched Dave's video a few yrs. ago .

    I have one of each variac & iso trans ;)

    Haven't gotten around-to-it yet , but use to build a dim-bulb-tester .
     
  5. KI7TGX

    KI7TGX Ham Member QRZ Page

    OK, I am agnostic on what is best. Clearly there is a ground loop; as to how bad that is I don't know. I am reluctant to alter the grounding of a consumer product, but tell me how to do it anyway. What do I remove where? I know I suffer from high noise, but assumed it was all the hash from the environment rather than this loop, which I have always known in the back of my head exists.
     
  6. W9WQA

    W9WQA Ham Member QRZ Page

    tv technicians used to plug a scope into an isolation transformer and then connect the scope to a hot chassis tv putting line volts on the entire scope!!!
    scope should always be grounded. the item being checked can be on isolation,NOT THE SCOPE!!!
    and no special probe is needed, just use regular 10:1
     
    K0OKS likes this.
  7. WA7ARK

    WA7ARK Ham Member QRZ Page


    No, I am making the point that you keep ignoring. The #$%^$ loop exists if you install the jumper in the Astron or not! You also keep ignoring the fact that the DC current around the loop is insignificant, and is too small to cause any problems, Gavanic or otherwise. Your lack of understanding basic electrical circuits is showing!

    ground.png

    Above is a simplified schematic of the grounding paths in my station. It is actually a bit more complicated than that, because there are several other 120Vac-powered accessories than shown. I have circled in red the one connection that would be affected by adding/removing the Astron jumper. All other the other connections shown as a black dot remain.

    With the jumper in, the negative side of the electronic regulator is tied to the chassis, and in the other case it is not. If it is in, the worst that happens is that the BLK power wire running between the ham rig and the Astron is paralleled first by two short ground straps and a piece of my fat copper bus bar, second it is paralleled with some coax connections (can you trace that?), and only third is it paralled by the external "Code-required- Loop".

    Regardless of the jumper in/out, the chassis of the Astron is connected to the wall outlet ground pin, and is connected to the Ham Rig (because they are both bonded to the station ground bus bar.) The "ground loop" you seem to be so worried about exists regardless if the jumper is in/out. The "loop" is mandated by Code; you cant do anything about it if you choose to comply!
     
    Last edited: Oct 31, 2019
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  8. AI5DH

    AI5DH Ham Member QRZ Page

    You are full of it. There is absolutely no code requirement, you are making that up. I know because I sit on code panel 9 and a licensed electrical engineer of 40 years. You still do not understand what you are talking about. NEC have absolutely ZERO, NOTTA, Zip, Nothing to say about plug and cord connected equipment. NEC stops at the wall receptacle. So get your story straight, because that is completely false and anyone with common sense would know NEC codes apply to building wiring systems, not gizmos you plug into the wall. That is pure BS and I call you on it. FYI equipment gizmos are certified by UL and CE. Not within NEC scope or jurisdiction.

    Nor do any electrical codes require you to make dangerous loops in your home as you have done. Nor do the codes prevent you from doing what you have done. Perhaps we should look at that. What you have created in your drawing is a complete mess with good intentions. You have intentionally and unintentionally bonded AC & RF ground together many times. You completely destroyed the whole purpose of an RF ground free of any current or voltage aka noise. You are intentionally polluting your ground system on purpose. That is what loops do. . But here is where you went wrong because you do not understand the intent of the code. You would be correct the code requires AC and RF ground to be bonded to each other as the code does not allow any form of isolated Ground Electrode System aka GES. All electrodes must be bonded to form a common electrode which you have done correctly. Figured it out yet? You think AC and RF must also in addition must be bonded again above ground in your house. Have any idea how dangerous that is.? AC and RF are already bonded together underground and use the same GES. You have intentionally created a parallel path for lightning to come in, have a look around, and a place to exit. .

    Lastly you do not understand the difference between a DC and AC loop. With the Jumper in, DC Current will flow in the ground conductors because you have now bonded Negative to Ground Twice creating a Loop. Current can only flow if there is a point to enter, and a point to exit. This is why electrical codes do not allow you to bond the neutral twice because it will force current onto ground something forbidden to do. Here is the point you still do not get. I just pointed it out, with the jumper installed bonds the Negative conductor twice to ground. Negative is also bonded internally to your radio point 1. Put the jumper in makes point 2. Now you have put ground in parallel with negative and current will flow in ground conductors. Take the Jumper out, and absolutely no DC current flows as it is only bonded once to ground inside your radio, thus no current can flow in an open circuit.You cannot do anything about the AC Loop, but you can stop the DC loop by removing the jumper.The radio bonds the negative making it neutral, not you or the power supply.

    Last thing in the world you wanna do intentionally is set up a good ground electrode system that spans half the distance of your house to have so you can have access to it at both the AC Service and shack, then run a jumper inside bonding one end of the electrode to the opposite end. That is a clear path inside for lightning and noise. Defeats the whole purpose.

    That will be $100 for your education and consult fee. :D
     
    Last edited: Oct 31, 2019
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  9. WA7ARK

    WA7ARK Ham Member QRZ Page

    Ok EE student (that's you Dereck). I (your EE professor) have an assignment for you:

    Draw out how you would connect up a typical ham station. Assume the same list of equipment I show in my diagram: An AC-line-powered desktop computer, 14Vdc powered ham rig, an AC powered 14V DC power supply, a tuner, plus an AC line-powered HF amp and other station accessories, a backyard tower, with an entry panel and coax runs. Include a best-effort RF Single-Point-Ground at the entry panel. Make sure it conforms to electrical codes, and offers best practice grounding for lightning protection.

    Submit it here for all of us to see. I will grade it.

    If you are unable, or unwilling, then quit posting this BS!


    Oh, and there is absolutely a code requirement that there be an Ohmic Path from any AC wall outlet to the electrical service ground rod, and that there be a cross tie conductor from any antenna-related ground rods to the electrical service ground rod. What are you blabbing about?
     
    Last edited: Oct 31, 2019
  10. K5EMG

    K5EMG Ham Member QRZ Page

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