antenna grounding

[stevolene]

Im putting up a scantenna this week, I plan on using a couple of 10' sections of aluminum top rail, I will bury the bottom section about 3', bolt the top section on, use a mast brace to attach to the side of the dwelling, no guy wires; as this will not be permanent, I wont be setting the mast in cement, Ive done some research and my question is about grounding.

My plan was to purchase a copper grounding rod, and bury most of it about 6" from the bottom of the mast, then use some braided strap, bolting one end to the mast, and attaching the other end to the exposed ground rod, would this be a sufficient ground?

Or, will I be wasting my money on the ground rod as the mast itself will be buried in the ground? Im a little confused about this process, and want to make sure this install will be as safe as it can be, the feed line will also be somewhat mobile so during a storm I could actually roll it up and have it disconnected and outside the house, any help would be appreciated

 

[OceanaRadio]

Im putting up a scantenna this week, I plan on using a couple of 10' sections of aluminum top rail, I will bury the bottom section about 3', bolt the top section on, use a mast brace to attach to the side of the dwelling, no guy wires; as this will not be permanent, I wont be setting the mast in cement, Ive done some research and my question is about grounding.

My plan was to purchase a copper grounding rod, and bury most of it about 6" from the bottom of the mast, then use some braided strap, bolting one end to the mast, and attaching the other end to the exposed ground rod, would this be a sufficient ground?

Or, will I be wasting my money on the ground rod as the mast itself will be buried in the ground? Im a little confused about this process, and want to make sure this install will be as safe as it can be, the feed line will also be somewhat mobile so during a storm I could actually roll it up and have it disconnected and outside the house, any help would be appreciated

You are probably sacrificing 3' of antenna height by sinking the mast in the ground, at least you are wasting it if you also add a ground rod. Static charges build up on a mast and a ground rod isn't necessary if the mast was buried, especially if below the frost-line. But for lightning protection a mast should always be grounded by at least one 8' ground rod. Perhaps your 20' mast does not protrude above the home roof or may also be surrounded by tall tress, in which case the mast could not be struck by lightning. Those are your possible conditions. Sinking a ground rod 8' into the earth can be a challenge due to tree roots, rocks, etc. However it is not an option (it's mandatory) if the mast is subject to a direct attachment by lightning. If that is the case then three 8' ground rods in a "Y" pattern each 16' apart would be best, and the mast must also then be bonded to the AC service entrance ground. Probably overkill for a 20' mast, unless it is the highest object within a 150' radius, in which case you have just installed a lightning rod.

Rgds,
Jack

 

[stevolene]

thanks, it will be surrounded by tall trees, it will be just slightly higher than the roofline of the house, I figure that will be better than the dipole Im using inside my bedroom now, Ill bury the mast a foot and give my self 2 ft in height, and use the 8ft ground rod, Ill post some pictures of this new adventure once I get this up, thanks for your response

 

[stevolene]

one other point though about lightening strikes, you say that being lower than the tree line the mast doesnt stand a chance of being struck, Im not so sure about that, Ive seen lightning strikes on eaves of houses, as well as shorter trees surrounded by ones much taller, I dont think theres really any way of acually predicting where lightning may strike

 

[comsec1]

strap

be careful using the braided strap outdoors as it will quickly corrode, you would be better off using a copper strap or at at a minimum 6ga solid copper.

 

[Raccon]

Ground me

 

[hoser147]

If you have an older house that has had a tower up at one time or another take a look around you may already have an un used ground rod already around the house. I knew I had one in the ground and used it. At a later time i was diggin for some landscape work and found another one just below the surface of the top soil. Hoser

 

[stevolene]

does anyone have any actual photos of the way thier antenna was grounded? the more I read on here the more confused I get, Im starting to think the mag mount on a pie plate is a better choice than all this hassle

 

[scrotumola]

If you have an older house that has had a tower up at one time or another take a look around you may already have an un used ground rod already around the house. I knew I had one in the ground and used it. At a later time i was diggin for some landscape work and found another one just below the surface of the top soil. Hoser

Just make sure that its a ground rod and not a surveyor's spike. A friend made that mistake. The spike even had a clamp, which we later found out was to hold a flag for the title company to photograph when the property was sold.

 

[Raccon]

does anyone have any actual photos of the way thier antenna was grounded? the more I read on here the more confused I get, Im starting to think the mag mount on a pie plate is a better choice than all this hassle

Click the link in my post above and then the two links at the bottom. No photos but they are pictures.

 

[jim202]

If you have done your homework, you would have found out that your home owners
insurance will have a clause in it about antennas. If you have done your homework,
you would have been pointed to the NEC (National Electrical Code) for grounding.

Bottom line is that any antenna structure, be it a mast from the ground, tripod on
the roof, tower or what ever, all require to be grounded. The big question is
how. Your homework should have produced information about soil resistance.
This is the sole determining factor on just what you need to get a good ground.

How is a good ground defined? That will depend on who you talk with. If you
ask 10 electrical engineers, you will probably get 12 answers. It is not an
exact science, but a learned talent. Most of the books talk about looking for
a ground system having a measured resistance of 25 Ohms or less to meet
the electrical code. If you bring in telecommunications into the picture, this
number jumps down to 5 Ohms. So you see it is not a simple answer.

As one person on here gave you the information of laying out ground rods so
the distance between them was 16 feet. This number comes from the cone
of influence around a ground rod. This cone is generally about a diameter of
the length of the ground rod. So if you use an 8 foot ground rod, the cone
around this rod will extend out 8 feet. If you place another ground rod
closer than the edge of this cone, your waisting money. The ground rods
will not get the maximum resistance benefit from the soil, as they are
overlapping. So we come up with the rule of thumb of spacing the ground rods
at twice their length apart.

If you have poor soil like sand, this doesn't provide a very good low resistance
to a ground rod. In the sandy soil, it may take ground rods of greater length
to obtain a good low soil resistance.

I will give you a case of just the opposite. In a location about 34 miles north
of New Orleans, there were 2 500 foot communication towers. When I joined
the company that owned them, they were having damage done to the paging
and cellular equipment located there. The towers were well grounded with
a ring of rods and solid copper wire around both towers and the equipment
shelters there. It took digging a ditch in opposite directions away from the
towers and adding a number of new ground rods. The soil was clay, with
the water line about 6 inches below the surface. Couldn't ask for a better
low resistance soil. However the problem was that the soil couldn't
dissipate the large charge that lightning placed on the ground system
when the tower took a strike. The added radials added to the ground
system was able to dissipate the charge and all was functional after
the strike. Yes you can take a direct hit and stay ticking.

Jim

Im putting up a scantenna this week, I plan on using a couple of 10' sections of aluminum top rail, I will bury the bottom section about 3', bolt the top section on, use a mast brace to attach to the side of the dwelling, no guy wires; as this will not be permanent, I wont be setting the mast in cement, Ive done some research and my question is about grounding.

 

[rfradioconsult]

A direct connection between your aluminum mast and your copper ground will cause corrersion that will render your connection useless. An electrical supply store can provide you with a CU/AL transition to eliminate the problem. I second the advice read and heed the NEC, rest assured your insurance company will. You can check your local soil resistance by using the ground fall method.

 

[btritch]

You can check your local soil resistance by using the ground fall method.

Ground Fall method?

 

[rfradioconsult]

Here is a link that should either answer your questions or will generate a bunch more. Warning do not attempt to read prior to bedtime!

http://www.omnicontrols.com/articles/Megger-Measuring_Ground_Resistance_Fall_of_Potential_Method.pdf

 

[af5rn]

Ground Fall method?

ROFL! :lol:

Yeah, that's where you take a swan dive off of your roof, head-first into the ground. You can get a real appreciation for soil resistance by this time-proven method!

 

[stevolene]

well Ive done my homework, decided that putting up a 30' scantenna is more BS than I wanna deal with, I have 2 of these antenna's, what a waste of money, Im gonna put them in the front yard and maybe someone will buy them yard sale style, till then Ill listen to whatever I can using a pie plate and a pmm3, man its not a wonder more people have been killed before cable and sattelite TV came around, back then you had to have an antenna to watch television, I asked one fellow that had an old antenna up about taking soil samples, he told me didnt need to, had no problem growing tomatoes and cucumbers