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Grounding base antenna for Yaesu FT-7900R

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Montgomery County TN
#1
I have a 15 foot 1.25 inch mast pole that I will be attaching a Comet GP-1 to. The pole is mounted to my deck. I will be using a length of coax about 55 ft long. My question is how should I properly ground the mast pole or should I worry about grounding it. Keep getting different answers while researching matter online? Thanks in advance.

Stan
73's
 
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Mass
#2
Attach a clamp to base of mast and use 6 guage copper wire run all the way to the electric company ground rod location and clamp it to that using your own clamp (do not loosen electric company ground wire). Then on the coax run put in a ground block which also bonds to that same ground rod location. This way there are no grounds with a difference of potential.
 
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New Orleans region
#4
Attach a clamp to base of mast and use 6 guage copper wire run all the way to the electric company ground rod location and clamp it to that using your own clamp (do not loosen electric company ground wire). Then on the coax run put in a ground block which also bonds to that same ground rod location. This way there are no grounds with a difference of potential.
It's not a good idea to have a long ground wire between the antenna mast and the common point
of the electrical meter ground. The NEC (National Electrical Code) provides for a common bonding
of telecommunications equipment grounding system to the electrical service ground. It does not
suggest or even imply that this should be the only source of earth ground for the equipment.

You would be much better off to provide your own ground rodS to ground your mast before going
to the meter service ground. You notice that I used the plural term of multiple ground rods. The
chances of getting a good low resistance earth ground with only one ground rod is rather low.
So you would be better off with multiple ground rods spaced at an interval of twice their length.
What this means is that if you are using 8 foot ground rods, you space them 16 feet apart.

You can use the distance between the electrical meter and your antenna mast for the ground
rod spacing. It will do no good to drive the ground rods closer together. The cone of influence
is where the spacing comes from. If you space the rods closer, the cone of influence from
each of the rods will overlap and reduce the effective low resistance gained by the multiple rods.

Another reason to space the rods is to allow for the high current dissipation if you ever take a hit.
The soil around a ground rod will have a tendanancy to turn to glass trying to get rid of the high
current. If the rods are spaced to the max extent of the cone of influence, the ground has a better
chance to absorb the high current from a strike and be able to dissipate it easier and faster.

Jim
 
Joined
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So Cal - Richardson, TX - Tewksbury, MA
#5
The NEC is very specific about using the electrical service ground to the point of requiring any additional ground rods to be bonded to the service ground. There are maximum wire lengths and minimum wire size for bonding antennas and ground rods. Its all in the NEC.

It "might" be possible to ground an antenna mast with multiple ground rods, lightning arrestors, straight runs of large conductor ground wires, etc to the point where the radio could possibly survive a direct hit but without the entire house properly bonded to the antenna system, everything running on AC in the house would probably be toast due to the difference in ground potential between the antenna and service ground.
prcguy

It's not a good idea to have a long ground wire between the antenna mast and the common point
of the electrical meter ground. The NEC (National Electrical Code) provides for a common bonding
of telecommunications equipment grounding system to the electrical service ground. It does not
suggest or even imply that this should be the only source of earth ground for the equipment.

You would be much better off to provide your own ground rodS to ground your mast before going
to the meter service ground. You notice that I used the plural term of multiple ground rods. The
chances of getting a good low resistance earth ground with only one ground rod is rather low.
So you would be better off with multiple ground rods spaced at an interval of twice their length.
What this means is that if you are using 8 foot ground rods, you space them 16 feet apart.

You can use the distance between the electrical meter and your antenna mast for the ground
rod spacing. It will do no good to drive the ground rods closer together. The cone of influence
is where the spacing comes from. If you space the rods closer, the cone of influence from
each of the rods will overlap and reduce the effective low resistance gained by the multiple rods.

Another reason to space the rods is to allow for the high current dissipation if you ever take a hit.
The soil around a ground rod will have a tendanancy to turn to glass trying to get rid of the high
current. If the rods are spaced to the max extent of the cone of influence, the ground has a better
chance to absorb the high current from a strike and be able to dissipate it easier and faster.

Jim
 
Joined
Aug 7, 2010
Messages
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#6
I have a quick question.. how do I do all this grounding outside the house? How far away from the foundation should the ground rods be? And would I run a 6 gauge wire from my mast down the side of the house and then across the grass to the grounding rod (making an 'L' shape) or would I run the wire directly from the mast to the grounding rod (making a 45 degree slope)? Also, in my case, the electrical ground appears to be a think wire running into the floor of my basement about an inch away from a water pipe which also run directly into the floor of my basement. Likewise the cable and telephone have attached their grounding wires to that water pipe! So then how do I connect my grounding rods to the electrical ground? Do I dig up my floot around the water pipe and hope to find a grounding rod under the floor to clamp my wires to or can I just clamp them to the water pipe?
 
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Messages
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#7
well, I just read this: http://www.swssec.com/grounding.html
and this is very discouraging. I honestly don't think I am ever going to be able to ground a single 10 foot mast, and I am starting to think I shouldn't. If I do it wrong it could do more harm than good. I think I will use lightening arrestors, and RF ground my radio, but other than that there's nothing else I can do.
 
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Joined
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1,542
Location
NW Ohio
#8
A water pipe is a very poor choice for a ground. There may be plastic pipe between your house and the water main which would result in no ground. In fact, the water main itself may be plastic.

A lightning strike will behave like a very high frequency RF wave. It has a very fast rise time and fast current fluctuations. Any bend in the ground wire will act as a choke and cause a voltage drop across the bend. You want to run the ground wire as straight as possible from the object you want to ground to the ground rod.

When talking about ground rods, more is better. Earth doesn't make a good conductor and its resistance changes with the amount of water in the ground, more water = less resistance. Each ground rod should be copper or copper clad and about 4 to 6 feet long. The rod should be driven down until the top is about 6 to 12 inches below the surface. Again, more is better so use more than one ground rod and bond them all together. The rods will be in parallel and lower the system's resistance to ground.

High frequency RF current tends to concentrate on the surface of a conductor with very little traveling in the core of the conductor. For this reason, stranded wire will furnish a lower resistance path than solid of the same gauge.

Your object isn't to keep lightning from entering your shack, you won't be able to do this. Instead, when lightning hits your antenna, you want the voltage on everything in your shack to rise together. This will keep current from flowing through your equipment. So bond all of your equipment, all of the grounds (AC, water pipe and earth) together at one common point.

This is a lot of work and can be expensive. It still won't guarantee that you will never have lightning damage but it should reduce the chances.
 
Joined
May 14, 2012
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Location
Virginia Beach, VA
#9
I see this thread is from almost two years ago...but I've been poking around the net trying to research how to go about making all of the appropriate grounds for my system. I don't have it up yet, but I have a J-pole I'm planning to mount on my chimney. If I were to run a wire straight down from the mast, it would be going into concrete; closest ground is +/- five feet from that point, so I too would have an "L" bend in the ground wire.
 
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