Hf Antenna Grounding

[Derrick Drescher]

Ilive in an area where lightning is rare, but not unheard of. Should I drive ground rods into the ground for antenna/RF grounding? The antenna itself has several small ground radials, so I'm assuming that a good ground will aid performance, but don't know if using the existing building ground is "good enough".

I live in a multi-unit building which may complicate this since my understanding is that any antenna ground system should be bonded to the building ground to prevent differing ground potentials (and the bonding should be via a dedicated ground wire directly to the building ground, not through a ground conductor in the building wiring), however my building ground rod is in a separate structure. The service entrance is in a closet in the back of a garage structure, then it goes under a sidewalk and my front yard and then into a service panel in my kitchen in the middle of the house (either under or through the cement slab). There's no apparent grounding electrode for the living unit, and even if there was, there's no easy way to run a ground wire from the antenna to it since I'd either have to go around a neighbor's unit or over the roof to reach it. It is possible that the service panel is grounded to the slab rebar or to a ground electrode that's not visible.

My housing complex looks something like the diagram below (though there are more housing units than what I've drawn), where I'm in unit 2 and would mount the antenna outside a room on the back side of the unit, while the service entrance comes in from the garage on the other side, The "V" shows the location of the service panel inside the unit:

Since I'll be using it with a 12VDC mobile transceiver, I could conceivably keep the tranceiver isolated from ground, leaving the antenna & transceiver ground completely separate from the building ground, but that seems quite unsafe if there is a difference in ground potential between the back yard and front yard.

If the lightning hits the antenna, have the same problem in the other direction. The important thing to realize is that the current from a lightning strike is so huge that it will go through all the grounds, and if one of those paths is through your equipment, expect something to be broken.

You might even be making things worse by adding a ground (B) to your station. Now your radio is part of the safety ground for your house's electrical system, even if you disconnect the feedline (A). Don't do that!

Grounding the antenna won't improve its performance. The important thing is to eliminate common-mode currents in your antenna system, perhaps with a balun. Once you've done that, there won't be any need to ground the antenna for performance.

A proper lightning protection scheme requires that you take all cables entering your station, including the feedline, AC mains, ethernet, telephone, and anything else, and passing them through a common ground point which is bonded really well with the Earth (read: multiple ground rods, wide, short copper strap). With only one ground connection, there's no path through your equipment, only around it.

This is costly and time consuming, and given your specific situation (relatively small VHF antenna on what I assume isn't an especially large tower, in a region with rare lightning) it may be difficult to justify the expense and effort.

If you don't add more grounds (such as B in the diagram above), then you can be reasonably protected by disconnecting the feedline. Your station at least won't be any more vulnerable than any other device you leaved plugged into mains, like your TV.

Given what you have presented, yes, put a ground rod down and bond the mast to it.It would also be a good idea to attach a ground wire from the radio (one of the mounting screws will do) to this same ground rod.Your power supply should have a 3 pin plug on it for connection to the building AC; one of these pins (usually the round one) should be the "safety" ground running back to the distribution panel and its earth ground. You should have no trouble here unless you mount your radio to the power supply (keep them isolated from each other).

There are many articles on the net about grounding; what you are trying to create is a single point ground for your system. At VHF and UHF this is not as critical as at HF frequencies (read up on ground loops).

It is always a good idea, if bad weather is in the area, to disconnect the antenna feed line from the radio and isolate it or ground the center pin of the coax to your new station ground. Keep in mind that if your antenna is the tallest thing in the area it may / will become a lightning rod.

What you need to know and understand about Grounding or Earthing your Home TV Antenna. This can be a very confusing subject with all of the misinformation and often times dead wrong explanations found on the web. Don't be intimidated, its easier than you think. Below is a video I made showing my set up. I'm not an expert, but I have learned how to ground a home tv antenna and it worked when I needed it to work. An updated video is below.

This link takes you to a publication that tries to clarify the NEC Article 810 mumbo jumbo concerning tv antennas and can still be very confusing. What we as home dwellers need to be concerned with is in this document so read everything. Should you have any doubts, consult a qualified electrician that understands antenna grounding. Be Safe, Not Sorry.

To explain my setup: I will be installing a gable antenna mount which has a 6' extender pole on my single story home. The antenna is 3.7ft tall for an overall height of approximately 24.7ft above ground level. My location is 177ft above sea level which puts my antenna 201.7ft above sea level. I am on a hill which is at a higher elevation than a lot of the surrounding area. There are nearby trees which will extend to higher altitudes than my antenna.

The antenna itself is grounded with a DC ground, but I need to know how to tie this in and create a proper ground. I do not wish to damage my home or radio equipment because I ignorantly installed my ground.

I might add that my antenna will be on the same side of the house as my power company box, so their grounding rod is available to tie into. Would this be advisable? If so, what is the best way to connect my antenna to the grounding rod?

It is against the electrical code in most jurisdictions to tie anything into the power company grounding system. Don't go there. If a 'meter reader' walks by and sees that tie-in, it could be a bad situation financially with fines, etc.

One accepted method to ground your antenna system is to run a 4 gauge ground cable with lugs on both ends from a U-BOLT where the antenna attaches to the mast, and then down to the standoff gable mount bracket U-Bolt. Tape the 4 gauge cable to the mast. Then continue with another length of 4 gauge cable from the gable mount U-Bolt down to an 8 foot ground rod that is out by at least 1 foot from your foundation. It should also be a minimum of 10 feet away from the power company ground rod. This is necessary to distribute a lightning hit into the power company equipment away from a lightning hit at the same time into your antenna structure. Having ground rods too close together may create a high electrical pressure wave against your foundation or slab during a strike and cause cracking or an actual failure. I have witnessed this personally in Michigan.

Some older hams have refused to ground their antenna systems at all. The thought behind this is that a bolt of lightning is going to seek out the best and easiest path to ground. Grounding an antenna structure makes it into a lightning rod and may actually attract lightning. Some old school hams also remove the antenna connector from the radio and place that connector inside a GLASS Mason jar so it will not contact a metal surface in the room during an electrical storm. There have been countless discussions about this over the years, and it just may continue here now that I have mentioned it.

That sounds plausible for a base station where you will only connect it when you use it, but eventually my antenna will be used for my repeater. Since I will be leaving the repeater on most of the time (and I live in Florida close to the lightning strike capital of the country) it would not be advisable to use this method. I should go ahead and ground the system properly now so I don't have to go back and do it in a few months anyway.

I think I will take the advice to run the 4 gauge wire to the grounding rod. Its going to be difficult to get a grounding rod that distance from the house (and the other grounding rod on this side of the house) without getting it in lawnmower territory. Would hate to forget my grounding rod is there and run over my wire with the mower. Thats something I will have to figure out.

Underground would be fine for a relatively short distance and you can do a large radius bend where necessary to change directions. Before you dig, contact your equivilent to "Diggers Hotline" to have current underground utilities marked. Then, when you are finished with the digging and routing of the ground cable, take the little color coded flags that they usually stick in the ground to mark gas, water, electric, phone and cable lines, and mark the location of your ground rod with one of the flags. Spray the flag danger orange with no printing visible and it instantly becomes a warning for the lawn mower. You CAN actually bury the ground rod completely if the flag idea won't fly, but make a detailed measurement map with landmarks as to where it is burried and place that map with your critical household papers for future reference.

again this has been my experience in the north east, where you are in FL is probably a completely different matter. for a control station w/antenna 15' above the roof line I wouldn't sweat it too much.

You guys make 2 very good points. On one hand proper grounding is a good idea, while on the other hand ground provides a path of least resistance. If I ground the antenna properly then I would surely be saving radio equipment if a strike were to happen, but at the same time I would be making my antenna a target since the lightning would have least resistance if it hit my antenna versus the tree 40ft away.

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