HAM radio tower

[jim dungar]

A co-worker is installing a 35' three-legged "lattice" steel tower. There will not be any rebar in the concrete base.

He is planning on connecting the tower to his existing water piping. I think he needs to bond it back to his service entrance instead.

For lightning protection (we are in Wisconsin which is not prone to frequent electical storms), some anecdotal literature says he should provide a ground rod for each of the three legs. I believe he only needs 1 5/8" rod, but I don't know much about grounding specifically for lightning protection.

Any suggestions?

 

[hbiss]

Re: HAM radio tower

If this is bracketed to the building I would treat it the same as any other antenna installed on the structure. If it is more than 20 feet from the service entrance drive a supplemental ground rod at the base of the tower and bond it to the service ground.

I'm not clear on how the water piping would be easier to bond to.

-Hal

 

[hurk27]

Re: HAM radio tower

Jim The problem with this is each installation requires analyzing the tower and surrounding area and close by building's. as well as the design of the lead in cables and how they are brought into the building and or radio room.
Multi-point to Earth grounding as well as radials (crows foot) ran out from the tower base is one approach that works in most installation. and to keep all cables entering the building to one entrance point. after this a bond back to the service GE must be made and it is best if it is kept outside of the building. at the entrance point of the cables there should be a grounding bar installed and each cable that goes to the tower should be bonded to this bar which is also connected to the grounding electrode system. Bonding to the nearest water pipe seems like a good choice but it is not as this invites a lightning strike to enter the building to reach the Earth which is a No NO as lightning can arc off this pipe to anything inside and cause a fire and do even more damage if it arc's to the electrical system. I have a 80' tower with a total hight of 120' to the top of my antenna. I have 6 radials ran out 40' with a 10' ground rod at 20' intervals on each radial spoke. Also on the first 6 rods away from the tower I have a 5 gal bucket with the ground rod right through the middle buried 2' below the grade level with holes drilled in both tops and bottoms. each one has a round salt lick in it which when it rain's it dissolves a little at a time and keeps the ground very conductive. I have 5 computers on-line all the time and other radio equipment running and after several strikes I haven't lost one piece of equipment "Yet" as always nothing is guaranteed against a lightning strike but with the right design the damage can be kept to a minimum.
I know this wasn't what you asked for but I though I would give ya a little more.
If you like reading here is a good site that is all about lightning and protection:

National Lightning Safety Institute

 

[dereckbc]

Re: HAM radio tower

Jim, I will probable repeat a lot of what Wayne said, I design a lot of these systems for a wireless telco, but here goes with out theory and low budget style.

Drive a rod just outside each tower leg (3 in your case), bond each leg to its respective ground rod. Then run a ring around the perimeter with the ground rods and bond to each rod. If you can run radial from the rods outward, do so as far as you can.

Dig a trench along a path directly under the coax path from the tower to the entry point of the building, drive a rod where the coaxes will enter the building. Dig another trench to wherever the AC GES is. Bond a conductor to the tower ring or tower rod, run it to the ground rod at entry point and to the AC GES and finnish bonding.

At the tower, bond a conductor to the ring or rod, come straight up to a tower leg and install a ground bar on the tower leg. The closer to the ground the better. This bar will be used to bond all the coax sheaths as they leave the tower. Also bond the coax sheaths at the antenna up on the tower.

Run the coaxes as close to the ground as possible. For each foot above ground you can expect a voltage build up of 1000 volts or higher during a strike (oops theory).

At the building entry point, bond another conductor preferable two to the rod. Run one conductor to a ground bar on isolators, outside the building at the entry point as close to the ground as possible. This bar is used to bond the coax sheaths again and any associated antenna discharge units (highly recommended). If a second bonding jumper is used, run it inside with the coaxes to terminate to another isolated ground bar inside the Ham shack. This bar is used to reference a isolation transformer or a GP ground if needed.

Hint if you can find wide copper straps or braided cable, use it in place of solid or stranded cable on the bonding jumper to the ground bars. Minimum size for all cable is 6 AWG. Try to stay away from mechanical connectors if possible.

That's it, good luck... Dereck

 

[jim dungar]

Re: HAM radio tower

Got a few more details. The tower is located about 3' away from the buidling (house). The tower legs are only about 1' apart from each other.

I agree the water pipe is not the correct place to bond. There is only one co-ax going to the tower now, but who knows in the future. The coax will have the shield bonded just prior to, or maybe just after, entering the house.

With such a small tower base and the proximity to the building it looks like we will only be able to install one (okay maybe two) radial. If this is the case, do we need to bond all three legs together?

 

[dereckbc]

Re: HAM radio tower

Originally posted by jim dungar:
With such a small tower base and the proximity to the building it looks like we will only be able to install one (okay maybe two) radial. If this is the case, do we need to bond all three legs together?

I would via ring