Ground Strap or Ground Wire

Discussion in 'General Technical Questions and Answers' started by STDYIN, Sep 6, 2020.

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  1. STDYIN

    STDYIN QRZ Member

    to ground out Radio's
    is it better to use a Tinned Strap ? or stranded Wire ?

    I know im beating this to death
    BUT

    My Ground Buss-Bar inside for my radio's/equipment
    is going to be an old piece of copper plumbing pipe
    mounted on the wall

    does it matter if its in the pipe form
    or would it be better pounded flat ?

    Thanks
    John
     
    WB2WIK likes this.
  2. AI5DH

    AI5DH Ham Member

    They are all safety grounds. 12 AWG wire is more than enough.
     
    W6KCS and KQ0J like this.
  3. WA4ILH

    WA4ILH Subscriber QRZ Page

    The answer to your question is, No, it doesn't matter."
    Tom WA4ILH
     
  4. K4SRF

    K4SRF XML Subscriber QRZ Page

    Again, another vote for "no" it does not matter as long as it is properly grounded outside.
     
  5. W2WDX

    W2WDX Premium Subscriber QRZ Page

    Admittedly, I copied and pasted the following to limit typing: "Copper strap (or strip) is the conductor of choice for low impedance RF ground connections. Due to the skin effect, RF currents tend to flow along the outside "skin" of a conductor. Copper strap has a large, smooth surface area to take full advantage of this effect."

    Now this is for solid copper strap. Woven or braided strap is more flexible, but has a slightly higher inductive reactance compared to solid strap, but not by much. Wire is wire, and since at RF there is skin effect, the small surface area compared to strap has higher inductive reactance. It's fine for DC or near DC currents, but for any RF use it's not as preferred. Wire is fine for AC safety application ... not so much at RF.

    The issue is skin effect, so hammering a copper tube does not make it any less inductive. In fact there is reason to think a tube has more surface area than a flat bar, however that is highly speculative and I do not know for sure if there is any differences.

    I used woven strap, copper tubes, and for the longer runs flat solid copper strap with good effect on reducing RF currents in the station. Such as here while assembling this station in a commercial space where the ground was a direct connection to the service panel which had a rod outside. I used flexible strap since this station had various vintage radios swapped out on a regular basis, so I wanted the flexibility:

    [​IMG]

    On my current residential station, I use a 2" by 1/4" copper bar and 1" solid straps for the gear, across the back of the station; which is bonded to a 3" wide solid strap which runs about three feet to a bonded 8' rod directly outside the wall. Also attached to that rod are my antenna suppressors for coaxial (and OWL in the future). My 2M yagi is on the side of the house and has its own strap and bonded ground rod directly below it. The two station rods and the AC service rod are all bonded together underground by 4ga stranded bare copper wire.

    I will again emphasize the need and importance of having the outside ground electrode system bonded ... all outside ground rods bonded underground by at least 6ga wire. This is a safety concern and less a matter of RF mitigation. I do know you have already done this, so this is more for others reading this.

    Now simply saying it doesn't matter without any scientific proof is simply anecdotal and such statements should be taken with a grain of salt. I really think people need to read more before commenting on such an important issue that is broadly accepted on a commercial basis as well as required in the NEC; for reasons relating to the science; and not simply amateur conjecture or corporate marketing. RF grounding is a real thing that can be accomplished to a reasonable degree if certain criteria can be met, and to simply discount it because of anecdotes you heard over the years is simply inadequate.
     
    Last edited: Sep 6, 2020
    K0UO likes this.
  6. K1LKP

    K1LKP Platinum Subscriber Platinum Subscriber QRZ Page

  7. AI5DH

    AI5DH Ham Member

    I could not agree with you more. A great place for hams to start is ARRL Grounding and Bonding for Amateurs. It follows many of the proven professional techniques. In chapter Two defining terms defines RF Ground as:



    What is extremely important to understand is what a PLANE is. It has a few names like Station Ground Bar, Equipotential Ground Plane, Ground Window, or just a Buss Bar. No conductor or pipe can be a PLANE. The impedance between connections points along a length of a wire buss would be extraordinary high. The secret of a Plane is the impedance between any two points is essentially 0 Ohms. If you have 0-ohms between any two points on a plane, there is no voltage between those two points, thus no current flowing in equipment grounds. Everything remains at the same voltage, whatever that voltage maybe. The cable going to dirt can be tens of feet away. The bar in the shack is where the Station Ground Bar is located.

    The guide goes on to tell the ham radio operator to construct a Single Point Ground. What do some of you think items for sale like a Entrance Panel is for? That is the Ground Plane to reference everything too including the AC circuits. It can be a copper/aluminum hatch plate, A copper/aluminum sheet on plywood, or an actual Ground Buss Bar like every commercial operator uses.

    Everything inside the Shack is an Equipment Ground and is for Safety only.



     
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  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Unless you're trying for an "RF ground," which usually isn't necessary and can be nearly impossible on the higher bands much above 5 or 7 MHz, none of this makes any difference.

    But if you hammer a pipe flat, its skin resistance (for AC/RF) should be the same as if it was its original form; the skin perimeter doesn't change, even though the resulting shape does.

    In general, smooth conductors are slightly better than braided or stranded ones. Braided straps are commonly used in automotive vehicles to bond stuff (like engine hoods), but that's because they need to be flexible. If nothing is "moving," solid ones would be better.

    If you want a good RF ground for a tuner used for an end-fed wire or something (and I've done this), put the tuner outside, on the ground, bonded to radials on (or beneath) the ground. You can really achieve an RF ground that way. Trying to make this work with a tuner "in the shack" and away from earth ground is difficult.
     
  9. AI5DH

    AI5DH Ham Member


    I agree with you but for different reasons. You are not making an RF Ground, term thing again without meaning, you are making a Counterpoise. Using the Term RF Ground implies you are using dirt as a conductor, not possible. Bringing it inside is insane I think you would agree. Your tuner is not a tuner at that point. It is an active Antenna Element and the equipment ground wire is an active antenna element with RF current flowing. A single wire has very high impedance. Move the antenna two wavelengths away as you imply, and life is good. No active antenna in the shack.

    It is impossible and hams spend hours trying and wasting time.

     
  10. W2WDX

    W2WDX Premium Subscriber QRZ Page

    Again conjecture without any basis in fact.

    A "ground plane" is a different thing and I do not agree with the ARRL on this issue. A counterpoise is fundamentally different from an earth ground electrode. The former is an effect where the latter is an electrical condition. A counterpoise can be elevated and unrelated from a ground electrode. A counterpoise can exist when a ground electrode is not even present. It's a form of a floating ground relative to RF energy. A ground plane (counterpoise) usually is also a "tuned" element to some degree, which is why radials (a form of counterpoise) on a vertical is usually frequency dependent as far as wire lengths.

    Saying you cannot use dirt as a conductor is both incorrect and half true. The fact that lightning uses the potential difference between earth (dirt) and the charges in the cloud is why ground lightning exists. Lightning rarely goes out into space, with the exception of radiated plasma (sprites). However it will also travel within clouds, but that is due to charge differentials from convection within the clouds themselves. The fact that ground is established by a direct connection to earth (be it AC safety or otherwise) via rods also indicates earth is conductive. I say half true because it is not a perfect conductor by no means, which is the reason why bonding must be performed between ground rods to get the entire ground electrode at the same potential. The main point of a ground electrode is to dissipate energy more than anything, and secondly to establish a consistent zero potential (ground) point. A counterpoise in an earth station is not this.

    An RF ground is not "a term thing". It a goal. It's a reality. You could say having a 30A AC circuit is a term thing, however it's a goal that can be achieved by using the correct wiring able to handle those currents. That being said creating a RF pathway to a zero potential is similar, however creating one that is effective over a wide bandwidth is not easy and requires very specific design criteria. Much in the way a counterpoise gives an antenna something "to push off of" it is not the same thing as ground. Ground is ground, regardless of frequency. It is a point of zero relative potential. In order to normalize RF energy, especially things like broadband noise, you need to have a situation where inductive reactance is low on the circuit pathway. This is what makes it difficult to establish a zero RF potential and requires careful planning and design. Otherwise, the "ground" is invisible to the RF and any floating RF current ends up at a different potential. However, this is not to say it is impossible to achieve. If it was I would not notice a significant change in noise level on receive simply by connecting and reconnecting the main ground strap to my station buss bar. I have what would be considered a near perfect AC safety ground system in my household wiring, however, this RF noise presents quite noticeably without my station going directly to its own short low-reactance ground point on the electrode. This condition is regardless of AC filtering or even if I unplug every device in my home from the outlets.

    If you do not ground an antenna tuner, it is then and only then where it becomes an active antenna element, not the other way around. It's part of a floating counterpoise. Not having a ground buss inside means your non-grounded antenna lead "brings it inside" and also raises the potential for disaster since now only your AC safety ground becomes the pathway for any extra energy, such as lightning. That energy will go through your electrical wiring (after traveling through all of your station chassis) till it reaches the service panel, not a good condition. In addition, not having a bonded electrode system and a short length to that zero potential, means the ground wires of your entire house for all intents and purposes become a large fractal antenna that can conditionally radiate, over a wide range of possible frequencies. Not only is this a nuisance, but it also may have an effect on radiated patterns; as well as introduce noise into receive. The difference between a counterpoise and a ground, especially one that has the same zero potential at all frequencies as in a ground electrode system means there is no potential difference between that electrode and any ground buss or AC service ground, or antenna mast ground, antenna protective device, or equipment chassis. They are all always at the same potential. There is less chance of "bringing in anything inside" as far as safety. As far as RF, providing a short low reactance pathway to such an electrode means it also has nearly the same potential to ground, where the AC safety wiring of your house alone certainly will not provide such to RF. That is what it means to have a better RF ground. RF ground is not a thing or a phrase, it's a created condition.

    I think the problem here is people (including the ARRL) are confusing the concept of antenna counterpoise with electronic grounding. The two while related, are not mutually exclusive.

    Steve, what you are describing with your tuner example is using a counterpoise. You do realize that if you placed those radials fifty feet in the air and put the tuner up there with it the system would function the same. The tuner then becomes part of the counterpoise, grounded or not. That is different from establishing a zero potential ground, in fact that counterpoise might be at a different potential than the AC source ground in that set-up, unless of course you're on battery power where all of this is moot. Such as a in a satellite.
     
    Last edited: Sep 7, 2020

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