Tower/Antenna/Wiring and Grounding

Status
Not open for further replies.

btritch

Member
Premium Subscriber
Joined
Nov 27, 2006
Messages
1,876
Location
Paragould/Greene County AR
I have a tower with a CB antenna on it and also a scantenna and TV antenna...My Question is, The tower is 4' in concrete and in the ground....in a 4' by 4' square of concrete....DO I need to ground each antenna to the tower (or will this drown out the signal) or do I just need to ground the tower from the tower leg to an 8' grounding rod or will it be fine just like it is since it's already 4' in the ground in a 4' X 4' square of concrete...I never grounded it before but for lightning purposes I'm fixing to do it if it's not too late...Anyone have any ideas?

I'm going to throw this in, I've looked everywhere and can't seem to find them but I've ordered one before so I know someone has them out there somewhere, but I'm looking for a BNC female to BNC male adapter to go on my pro 97...I looked on universal radio and on testparts and I couldn't find them either place, does anyone know where to find them at online?
 
Last edited:

N1BHH

Member
Joined
Mar 31, 2007
Messages
1,843
Location
Jackson Square, East Weymouth, MA.
You should have several ground rods around the base, bonded to the tower with something along the lines of 2/O wire. And to improve ground conductivity some kind of ground screen, a simple one uses bare wire buried in the ground radially, using a lawn edger. If your CB antenna isn't attached electrically to the tower it won't have a route to ground for any static charge, except straight to your radio gear. Antennas have to be electrically connected for them to assist in static drain.
 

zz0468

QRT
Joined
Feb 6, 2007
Messages
6,029
Yeah, I have an idea. Get a copy of the ARRL Handbook, and the ARRL Antenna Handbook. They'll give you plenty of suggestions.

In the real world, each tower leg would be grounded separately, the separate grounds would be bonded together, and then the antenna feedlines would be grounded in 3 places - at the top of the vertical run, at the bottom of the vertical run, and at the building entrance.

No, grounding the antenna properly won't "drown out" the signal.
 

OceanaRadio

Member
Joined
Dec 19, 2002
Messages
150
Location
Virginia Beach, VA
btritch said:
I have a tower with a CB antenna on it and also a scantenna and TV antenna...My Question is, The tower is 4' in concrete and in the ground....in a 4' by 4' square of concrete....DO I need to ground each antenna to the tower (or will this drown out the signal) or do I just need to ground the tower from the tower leg to an 8' grounding rod or will it be fine just like it is since it's already 4' in the ground in a 4' X 4' square of concrete...I never grounded it before but for lightning purposes I'm fixing to do it if it's not too late...Anyone have any ideas?

I'm going to throw this in, I've looked everywhere and can't seem to find them but I've ordered one before so I know someone has them out there somewhere, but I'm looking for a BNC female to BNC male adapter to go on my pro 97...I looked on universal radio and on testparts and I couldn't find them either place, does anyone know where to find them at online?
Its easy to be confused by what "grounding an antenna" means. The antenna itself is always electrically isolated from the tower and any mast, mounting bracket, stand-off, etc. That is for RF-purposes it is electrically isolated -otherwise it could not radiate, it would simply drain down the tower as you suggested. However the common design of a DC-ground antenna does allow DC to pass from the antenna through the mounting systems and to earth. That's no protection system at all because lighting is predominantly at RF frequencies, and "static electricity" isn' all DC either. Just a gimmick that might spare the antenna itself from vaporizing in a direct attachment. All antennas have some kind of mounting design, and the only thing to avoid is isolating that mounting system from the tower. If you insist on using non-conductive extension materials to mount the antenna, then a bonding conductor from the antenna base-mounting fixture to the tower is required.

As mentioned above the coax shield does get bonded to the tower, and it usually happens at the feedpoint by virtue of the antenna mounting bracket (metal-to-metal contact from antenna mount where the coax connector attaches to the antenna, to the tower connection brackets). After that you have to make your own shield grounds at base of tower and building-entrance.

You asked if the concrete is a good ground. It is an excellent ground, and a 4'x4' concrete base has a hundred times more disspiation capability than three ground rods. However the 4' deep base is nowhere near deep enough to keep a majority of lightning energy from traveling horizontally outward fromn the tower base. Bad deal if this is right next to your home. Earth is a rather lousy ground in the first few feet of mostly dry soil and lighting takes a pass on shallow grounding systems because it saturates the first few feet of dirt (or concrete) so rapidly that the earth cannot hold any more energy at that immediate area. That's why the 8' deep ground rods (three at a minimum) are specified, even when a deep concrete base is present.

Finally, all tower and coax-shield gronding must bond directly to the building's AC-entrance ground rod, which should be at the same entry-point and common grounding location for all utilities entering the structure. By code-design all coax would enter the building there also, but we often enter coax at different parts of the home - at our own peril. Extensive bonding, grounding, and powerful AC surge-protection is required at both ends when coax enters a building far from the main AC entrance. It is the most difficult and expensive kind of protection design, because there are essentially two "single point grounds", one at the coax-entrance, and one at the home's AC-entrance. Lightning could have a field-day with that condition, and it takes a lot of copper to raise the odds that it won't.

Jack
 

btritch

Member
Premium Subscriber
Joined
Nov 27, 2006
Messages
1,876
Location
Paragould/Greene County AR
It is right next to the house unfortunately, All of the home utilities come in from a nearby pole in the yard and are not even on the house...I only have a 4X4 concrete square at this time for grounding, However I am looking at changing that, hence comes the 8' grounding rod suggestion, You've said I need three minimum.. Ok, I understand that however, How do I go about attaching them to the antenna structure or the tower?
 

N1BHH

Member
Joined
Mar 31, 2007
Messages
1,843
Location
Jackson Square, East Weymouth, MA.
I suggest you go to an electrical supply house or home improvement store and you'll find plenty of wire clamping devices. Get some heavy wire, as I said before 2/O, and bond everything together to multiple ground rods.
 

btritch

Member
Premium Subscriber
Joined
Nov 27, 2006
Messages
1,876
Location
Paragould/Greene County AR
So I need Three Clamps, Three Grounding Rods, And 2/0 Grounding Wire, clamp to the tower and then to each leg and then connect all three rods together, Correct?
 

OceanaRadio

Member
Joined
Dec 19, 2002
Messages
150
Location
Virginia Beach, VA
btritch said:
So I need Three Clamps, Three Grounding Rods, And 2/0 Grounding Wire, clamp to the tower and then to each leg and then connect all three rods together, Correct?
Three grounding rods at equidistant angles from the tower base do not require bonding between themselves. The tower base does require bonding to the ground rod used for the home's Neutral-Ground connection for the service panel. That ground rod will be right outside the home's AC service panel. There may even be two ground rods used there. Scrape the first few inches of soil away right outside the service panel and you will find it. Use a wire-to-ground-rod clamp (sold at Home Depot) to make that bonding connection. If the distance from the AC service entrance ground to the tower is more than 20' you need an additional 8' ground rod sunk at midpoint between them. 20' or less and #4 copper is sufficient, 10' or less and #6 is sufficient.

Jack
 

btritch

Member
Premium Subscriber
Joined
Nov 27, 2006
Messages
1,876
Location
Paragould/Greene County AR
that's the problem, I have my tower next to the house but they have got all the utilites for the house on the opposite side on a pole in the front, they're not even on the house at all... Would it help with a photo of what I have going on? I have thought about what has been said and in order to connect to the actual electrical utilites it will be very hard, they aren't even anywhere close, I mean it's a good 20 feet from the house to the pole where the utilities are and another 80 to 100 feet from the tower to the pole... Would it help with a photo or two?
 

n5ims

Member
Joined
Jul 25, 2004
Messages
3,690
btritch said:
I mean it's a good 20 feet from the house to the pole where the utilities are and another 80 to 100 feet from the tower to the pole... Would it help with a photo or two?
You're making this too hard, me thinks. Where in your house is your breaker or fuse box. That's what you need to look for, not where the utility wires are connected. If you have above ground wires, it's pretty easy to trace where they go into your house. If the wires are underground, look for a 3" (or so) pipe that goes into the house, generally just outside of where your breaker/fuse box is.

The ground for your house comes off your breaker/fuse box. This will go to a ground rod quite close to there, which is where you should think about bonding your tower ground as well. Some times, it is grounded to a water pipe, but normally is required to use a ground rod (8' long copper in most areas).
 

btritch

Member
Premium Subscriber
Joined
Nov 27, 2006
Messages
1,876
Location
Paragould/Greene County AR
Ok, I see what you're saying...The fuse/breaker box is in the middle of the house, I would assume the grounding is under the house...However, There are two plastic pipes of the same size just outside the other end of the house, I thought these were both sewer, One of them might be what you're talking about though but as far as the breaker box goes, it's right in the center of the house, Guess the next thing would be look under the house and see if I can see a ground wire connecting anywhere then..Right?
 

OceanaRadio

Member
Joined
Dec 19, 2002
Messages
150
Location
Virginia Beach, VA
btritch said:
Ok, I see what you're saying...The fuse/breaker box is in the middle of the house, I would assume the grounding is under the house...However, There are two plastic pipes of the same size just outside the other end of the house, I thought these were both sewer, One of them might be what you're talking about though but as far as the breaker box goes, it's right in the center of the house, Guess the next thing would be look under the house and see if I can see a ground wire connecting anywhere then..Right?
I can't help you with those conditions as I am not familiar with older wiring systems. The bonding of outdoor tower grounds to the AC electrical (breaker) panel does not apply to 2-wire systems or possibly to homes that were owner-upgraded from it, which might still not meet current code reqiirements. Unfortunately a homeowner can do just about anything under a grandfathered system, including the conversion from 2-wire to 3-wire. If the upgrade did meet current codes the breakers would have been moved close to the outside meter and very close to that location would be the ground rod. I'm not saying what you have is illegal, I just don't know how current NEC/NFPA codes and standards apply to it. You should consult a licensed electrician for further assistance.

Jack
 
Joined
Dec 26, 2004
Messages
1,217
Location
Tulsa
Take the money you would spend on a ground system and purchase an additional insurance policy for your radio equipment.
 

btritch

Member
Premium Subscriber
Joined
Nov 27, 2006
Messages
1,876
Location
Paragould/Greene County AR
It shouldn't be out of date or if it is it shouldn't be to far out of date, The house was built in 1997...I have thought about the additional insurance, Sounds like the best plan..Thanks For all the help Ya'll ! !! !!! !!! !! !
 
Status
Not open for further replies.
Top