Astron PS and Your Ground

Discussion in 'General Technical Questions and Answers' started by KF5LJW, Oct 29, 2019.

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  1. KA9JLM

    KA9JLM Ham Member QRZ Page

    Not sure why we need a thread that confuses most.

    What is most important. NEC or UL ?

    The best way is how you do it. Everything else is just a recommendation.

    Mother Nature determines what blows smoke. :rolleyes:
     
  2. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    I think that is a bit simplistic.

    Here is your second diagram from your post #82.

    Screen Shot 2019-11-03 at 4.06.23 PM.png
    The short 12 gauge jumper clearly creates a physical loop between the wall plate, PS, Radio, and ground rod. You said that since the jumper is short, there is no potential difference around this small loop, and from there to the RF ground rod, thus the equipment now has a single point ground and no lightning current or fault current will flow through the equipment.

    I agree this is an important and useful concept, but recognize that it's an approximation since the jumper has non-zero impedance and is in parallel with the equipment grounding path. There will still be a small current flowing through the radio equipment. (Ignoring time-varying magnetic fields through the loop for the moment, a different but very related topic).

    For my particular situation, the jumper must physically be longer, about 6 to 8 feet. Other hams might have a longer distance to traverse. So this brings up a question:

    What is the maximum length of jumper for which there is still an approximate equipotential and single point ground? Clearly the longer it is and the higher it's impedance, the less effective it is at creating an equipotential on the equipment loop and shunting current to the ground rod. Is it 2 feet? 6 feet? 50 feet?

    I think that the maximum jumper length is determined relative to the impedance of the other grounding conductors chaining the radio equipment together in the equipment loop. There are two parallel paths, and we want the impedance of the shorting jumper to be much, much smaller than the impedance of the other path around the equipment.
     
    KA9JLM likes this.
  3. KF5LJW

    KF5LJW Ham Member QRZ Page

    Then you did not red anything past that post where I detailed a method to bring both RF and AC Ground to the exact same place creating a Single Point Ground. So yeah it is that simple. Example I said:

    I know you are a smart guy and should understand that. None of the radio toys are in the Loop. All your RF and AC Grounds are all connected to the Loop at one point with a dedicated ground conductor. Your AC power Cords and Coax does the rest.
     
  4. N5TJD

    N5TJD XML Subscriber QRZ Page

    Of course you can really screw things up and throw in a rig interface and computer in to the mix... :p
     
  5. W4KJG

    W4KJG Subscriber QRZ Page

  6. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    Well, I don't think I missed anything, so we will just have to disagree in a friendly way. (BTW there are two loops, the big loop on the left and the small equipment loop, the size of which depends on the jumper length, which is what I was referring to).

    I do thank you for originating this thread, and also the shorting jumper idea. It caused me to review all of my grounding, which revealed the notorious grounded negative in another Astron supply that I recently started using (I should have checked but didn't). I have installed a shorting jumper which has dramatically cut down on the small AC leakage current that I knew I had through the USB connection. No doubt it has also improved robustness to lightning currents which is my main concern.
     
  7. KF5LJW

    KF5LJW Ham Member QRZ Page

    Perhaps you are talking apples, and I am talking oranges. The small loop on the right that you are referring too I would agree IF you are referring to the initial drawing. That would be a significant improvement vs where it would be without the bonding jumper.

    I am referring to what I later came back and eliminated the small loop bringing both AC and RF Ground together. There cannot be a Loop in a single point, it would require two points connected together to make a Line to form a loop.

    Or perhaps you might be referring to the Loop that would still exist after we move AC Ground to the Same Point? That I would agree with. However it is neither a good loop or bad loop. It is small and like the larger loop does not have anything circuits in its path. It would have exactly zero effect on the radio equipment because it is only connected at one point.

    So when said and done I think we can both agree if you were to bond the system as I suggest would do two things.

    1. Remove the radio equipment and all auxiliary equipment sharing AC power out of a Ground Loop.

    2. Create a pseudo Single Point Ground free of noise.

    You are welcome, glad I could help.
     
    N0TZU likes this.
  8. KI7TGX

    KI7TGX Ham Member QRZ Page

    can someone point me to a power strip with metal case bonded to ground so I can do as LJW says and place the ac ground very near to my shack ground and bond them via a short connection?
     
  9. WA7ARK

    WA7ARK Ham Member QRZ Page

    Plugmold is what I use.
    It runs parallel, just a couple of inches from the copper bus bar, full-width on the underside of the wooden table top that all my ham equipment sets on. The right end is bonded to the big wire that runs to the outside ground rod. Each piece of radio gear (radios, tuners, KW amp, computer) is tied to the bus bar using short runs of tinned copper braid, so that the metal cabinet of each item is bonded to the copper bus bar. The green wire ground in the plugmold is also bonded to the bus bar.

    Between the plugmold and the wall outlet, there is short heavy-duty AC-line-cord. The KW Amp runs on 240V, so it has its own 240V line cord.
     
    Last edited: Nov 4, 2019
  10. WA7ARK

    WA7ARK Ham Member QRZ Page

    I wired the ham shack as I built it, so I planned ahead for AC Power to the ham console. I have dedicated outlets right behind the ham console.

    I installed a duplex outlet with 2 separate 120V branch circuits, providing a maximum of 30A for the 120V loads. I installed a 240v 20A circuit for the KW amp. This gives me a single point of disconnect for servicing the equipment.

    Here is a picture from behind the ham console: The braid comes from the bus bar under the ham console, so is effectively in parallel with the green wires in each of the three line cords. The way it is wired, the copper braid is effectively in parallel with the green wires in the three line cords.

    I chose to run the big Astron RM-35M on its own AC circuit, while the Plugmold runs all the little stuff, including a Dell desktop, the monitor, PC speakers, various small DC supplies, clock, Antenna Rotor, remote tuner, etc... All of those are bonded to the Copper bus bar, as well as being connected to the green wire in the Plugmold via their respective line cords.

    wall.png

    With everything tied together as I have done, do you really think it makes one iota of difference if the negative terminal of the Astron power supply is strapped to is own chassis or not???? Especially, even if it is floated, the negative terminal of the Astron is effectively grounded to the chassis of the IC-7300 ham-rig by the 2ft black wire that runs between the Astron and the IC-7300.

    NOT
     
    Last edited: Nov 4, 2019
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