Ground loop?

[allenc4]

I want to operate some radio frequency equipment at my residence. The manufacturer and good practice specify that the RF equipment be provided a short, low impedance ground connection using a ground lug on the chassis of the equipment. My plan is to add bonded ground rods on the exterior of the structure and expose a grounded bus bar on immediate interior, keeping that connection short. I know it is required that the new ground be bonded with the existing ground system. I'm also aware that this ground extension bonding must be completed using irreversible splice connectors (Cadweld, compression type, etc.) I intend to have this electrical work done through a licensed contractor.

My question: if I take power for the RF equipment from an existing outlet and its existing ground wire located near the new ground do I need to worry about any sort of "ground loop" problem? The equipment will be connected to both the new ground (via the chassis ground lug) and the ground provided by the power outlet, and these two ground conductors would form a loop about roughly 25' in length to the point where the splice will likely exist.

I've done a lot of searching looking for insight on my worry, but haven't found any clear answers. I suspect the answer is no, I don't have to worry, but I'm not 100% sure about that, and I'd like to be.

 

[winnie]

Will this equipment radiate RF or will it use RF internally?

If it radiates RF then will you be using balanced or unbalanced antenna systems?

Is this a better question for qrz.com ?

Jon
AF7TS

 

[tom baker]

The AARL has a book on grounding, I have not seen it, just be aware there is a lot of bogus information on grounding
Ground loop is a term that is mentioned often, it can apply to audio equipment, not likely your radios
I would be much more concerned about antenna grounding and arrestors for your antennas
The ham radio installations I have seen rarely comply with the NEC on antennas and feed lines

 

[allenc4]

Thanks for your responses. After posting this I realized I shouldn't have; not a professional in the field and shouldn't be asking for help here.

winnie:

Will this equipment radiate RF or will it use RF internally?

A transceiver and supporting equipment.

If it radiates RF then will you be using balanced or unbalanced antenna systems?

I expect I'll have a variety of antenna connected over time.

tom baker:

I would be much more concerned about antenna grounding and arrestors for your antennas
The ham radio installations I have seen rarely comply with the NEC on antennas and feed lines

I am concerned about antenna grounding, arrestors and NEC requirements. Good information about these topics exist and I've inculcated this in my plans.

Anyhow, I'll take this elsewhere. Thanks again for your responses.

 

[winnie]

In general, if the actual electrical work is being done by a licensed contractor, theory question get a pass here.

The term 'ground loop' is usually applied to a _signal_ path which includes a grounded conductor that gets grounded at both ends. An example would be an RCA audio cable where the shield is connected to chassis ground on two components and also carries signal current.

If high level power line currents flow on this grounded shield, then this can couple to the low level signal.

You will have a shorted loop of grounded conductor if you consider antenna grounding, coax shield, and rig grounding. There are isolators that can break this loop but it generally isn't a problem unless the antenna is very close.

Depending upon the frequencies you are using, antenna grounding might be essential for antenna function or just there for lightning protection.

 

[synchro]

You might think about putting a clamp-on ferrite common-mode choke around the power cord that is suitable for the frequency bands being used. It's not likely to be necessary, but it could reduce possible conducted RFI / QRM in both directions.

Along the lines of what winnie has mentioned, if the antenna is properly fed then there should not be much RF current passing though your separate ground wire from chassis to the ground rods. If you have wire antennas, then you may need to have an appropriate balun so that RF currents do not return on the coaxial shield back to the shack.

 

[petersonra]

I want to operate some radio frequency equipment at my residence. The manufacturer and good practice specify that the RF equipment be provided a short, low impedance ground connection using a ground lug on the chassis of the equipment.

What is the purpose of this "ground"?

My plan is to add bonded ground rods on the exterior of the structure and expose a grounded bus bar on immediate interior, keeping that connection short. I know it is required that the new ground be bonded with the existing ground system.

probably true.

I'm also aware that this ground extension bonding must be completed using irreversible splice connectors (Cadweld, compression type, etc.) I intend to have this electrical work done through a licensed contractor.

There is no code requirement for this.

My question: if I take power for the RF equipment from an existing outlet and its existing ground wire located near the new ground do I need to worry about any sort of "ground loop" problem?

The ground pin on the power outlet is there to provide a return path to the circuit breaker feeding the outlet so in the case of a ground fault, the CB will reliably trip. That is all it is for, and is required. If it creates a ground loop, that is too bad. You still need the connection there.

The equipment will be connected to both the new ground (via the chassis ground lug) and the ground provided by the power outlet, and these two ground conductors would form a loop about roughly 25' in length to the point where the splice will likely exist.

Again, the question is what is this new "ground" for? The ground pin in the outlet should already be bonded to the existing grounding electrode system via the N-G bond at the service point. if you are worried about loops, you just added another one.

I've done a lot of searching looking for insight on my worry, but haven't found any clear answers. I suspect the answer is no, I don't have to worry, but I'm not 100% sure about that, and I'd like to be.

I think you need to start with why you are doing what you are doing.