Amateur radio antenna grounding question

[captain skip]

I read through the ARRL Grounding and bonding book twice, I reviewed Mike Holt's excellent write up and I still can't figure out the answer to my question. Maybe someone here has already done this and can let me know what you did.

I'm moving my antennas from my attic to a detached garage. I'm planning on mounting a vertical VHF/UHF antenna and an OCF wire dipole on a metal mast that is secured to a bracket on the gable end of the garage. The wire dipole would run from the mast to a tree in the backyard.

I will run a ground for the mast to a new ground rod and as I'm going to run two feedlines into a duplexer I'll install two Alpha Delta lightning suppression units prior to the duplexer at the base of the antenna. These will be grounded to the new ground rod. That part I've got figured out. This is where it gets tricky - or at least above my pay grade. The garage has my workshop in it and has a 100amp subpanel tied into the main house breaker panel. The main breaker panel is grounded to an Ufer ground in the house foundation. The subpanel in the workshop/garage has two ground rounds, bonded together, spaced 6' apart already in place. I plan on bonding the new antenna ground rod to the existing ground rods. The 100amp subpanel is supplied with #2 wire from the main house breaker panel and has a ground wire going from the subpanel ground bus to the main breaker panel ground bus which is grounded to the Ufer ground as mentioned. Do I need to run an additional ground wire from the ground rods at the garage to the Ufer ground on the house foundation? It's approximately 100 feet from the garage to the house. I have a NM conduit that I'm going to run the feedline through from the antenna to the shack in the house but running an additional ground wire is not really an option as I would have to cut/dig up a paved driveway to run the wire - which the Commander in Chief would forbid.

Second part of the question - As mentioned I plan on putting two Alpha Delta lighting units at the base of the antenna. Do I need to put another one where the feedline enters the house too? Attached is a rough (very rough) sketch of what I'm talking about. The dotted green line on the bottom is the extra ground wire that I'm asking about. I also plan on running an RFI ground from the shack to a ground then bonding it to the Ufer ground.

 

[LarryFine]

Welcome to the forum.

We're not permitted to assist with DIY electrical questions, but I think this is okay.

Do I need to run an additional ground wire from the ground rods at the garage to the Ufer ground on the house foundation?

No, you do not; to local rods is adequate. This is not an electrical power grounding conductor.

Do I need to put another one where the feedline enters the house too?

I don't believe so, mainly because it's underground. But, it couldn't hurt to do so.

 

[captain skip]

Welcome to the forum.

We're not permitted to assist with DIY electrical questions, but I think this is okay.


No, you do not; to local rods is adequate. This is not an electrical power grounding conductor.


I don't believe so, mainly because it's underground. But, it couldn't hurt to do so.

Thank you

 

[winnie]

As far as what is required by the electrical code, you do not require an additional bonding conductor between the grounding electrodes at the garage and the grounding electrodes at the home. The EGC run with the feeder to the garage is considered sufficient for this bonding.

As far as good design from a radio perspective, I only know enough to get into trouble. The issues with having two separate grounding electrode systems is that ground currents caused by nearby lighting strikes or utility equipment can enter one system, travel down any bonded conductors, and exit the other electrode. The general goal with grounding and bonding of radio equipment is 'single point grounding' where signal conductors are connected to ground electrodes at only one location. Not sure how best to achieve this in your situation.

There are several amateurs on this site, but I'd suggest exploring this in more depth at qrz.com.

73
Jon
AF7TS

 

[lanel]

single point grounding

In regard to single point grounding, I worked for many years on a point to point MAS system used by an electrical utility to communicate with substations and line devices and we had issues when using multiple grounds with stray current loops and stray voltages causing lots of damage during lightning storms. We had polyphasers on the coax which were grounded back to the substation grid but we also used to ground the metal antenna brackets. After repeated issues with lightning damage we found that by not having the additional ground on the antenna bracket that we no longer had the damage due during storms.

We also used to get lighting damage A/D systems using current loops if both ends were grounded. So we ended up grounding on one end and letting the other float and had no further issues.

I don't know if what you are proposing would cause any issues but if there is a possibility of having currents flowing through the grounds, you may end up with storm issues that otherwise you may not have.

 

[petersonra]

Just MNSHO.

I would not be adding another ground rod at the garage. I would just ground the antenna and the lightning thingies to the Intersystem Bonding Termination Device. See 250.94.

I don't see how running a wire between the two grounding electrode systems will accomplish anything. You already have a connection there via the equipment ground conductor.