Home antenna tower...

[BoxAlarm187]

I recently was able to pick up a antenna tower for my house for $100. It's worn, but appears structually stable, and after doing some research, it looks like it's a Rohn. Originally a 50' tower, I would now estimate that it's about 45 feet after being "removed" from it's former home (removed with a torch, it appears).

After doing some internet research, it certainly appears that the most important part of putting this tower up is the base in which it sits. What I am looking for is some idea on the dimensions that I need to follow in order to figure out the HxWxL for the cement base. Also, how much of the tower needs to be actually in the hole?

I am planning on putting this next to the 2.5 story next to my house, so I will be able to secure it to the chimney ... I'd like to avoid having to do guy wires, but will if it's determined to be necessary.

Thanks for ANY advice you all might be able to give!!

 

[KR4BD]

I have 44 feet of Rohn 25G tower up. It consists of 4 10ft sections and one 8ft section at the top. I dug a hole about 4 feet deep and about 2.5ft by 2.5ft. The bottom section goes 4 feet into the hole which I filled with over 2000 pounds of ready-mix. The tower is also attached to the frame of the house (with a Rohn Bracket for this purpose) at about 10ft above ground. It is free-standing and has about 35-40 pounds worth of ham antennas on it. These are mounted on a 2 inch galvanized mast which fits down through the top section and then mounts into a Ham-IV Rotor (inside the tower) on a rotor-plate about 3 or 4 feet down from the tip of the tower. When I put this up about 18 months ago, I bought factory NEW tower. I had a very similar installation up for about 18 years prior to this one and never had any problems. My tower is not guyed, but I would not want to go any higher without guying.

If your tower is used, BE CAREFULL!!!!!

Old tower often rusts from the inside out. Check this carefully! If it is rusted internally, I would not use it. For external rust, I would sand off all rust and paint with primer and follow with a rust proof paint. I have had good luck in the past using Rustoleum (silver). I have had several towers in my lifetime and find that new, galvanized tower will need to be painted after about 12-15 years.

Also, check all welds on any used tower. If welds are broken, it indicates the tower has been twisted in a strong wind storm and is hazardous to climb. You definitely do not want to put up a tower with broken welds.

It's a lot of work to put up a tower, so do it right and you will have few problems, short of a tornado or strong hurricane hitting your property.

 

[KR4BD]

Oh...One last suggestion.

I would be cautious about attaching a tower to a chimney. A tower will sway in strong winds and this is OK. But this swaying will weaken the mortar joints and water will get in. In no time, you will have leaks on your ceilings near the chimney. Then, the freezing and thawing of this moisture in the chimney will expand and contract the mortar joints and bricks will loosen and fall out... Now you will have to replace your chimney (not cheap!).

Been there, done that!

 

[RevGary]

BoxAlarm187 - just a thought - Call your local Weather Service Office and see what they have on file as the AVERAGE WINTER FROST DEPTH for your community. I would imagine that they can advise you of that. Once you know, the concrete base should be 12 inches BELOW the average frost depth so the winter to sumer frost movement will not affect the tower. At our Wisconsin location we had to go down 65 inches to meet the local code for 'footings'. Yes - it applies here to tower installs too (at least here locally). At our office in Florida, the concrete base was only 8 inches thick on a good tamped gravel underlayment because there isn't any frost, but it had to be 3 feet square to spread out the weight load because the water table is so high. Just something to consider for safety.

 

[Al42]

1) DON'T guy it to the chimney!
Chimneys have NO (read: zero) structural integrity. If it falls and damages something or hurts someone, your insurance company won't know you. Fasten it to the house - there are under-eaves connectors available.

2) The hole should be keyholed - 4X4 at the top, tapering to at least 6X6 at the bottom, at least 4 feet deep if you have it fastened to the house at the 16-20 foot level. Rohn sells a mounting base - use it. (I prefer adding a mounting plate, 6X6, at the bottom and bolting the base to that.)

Whether the tower needs guying depends on whether it's a free-standing tower or not - Rohn makes both kinds. If it's not free-standing, and you don't guy it, be prepared to pick it up off the ground.

Measure from the point you plan on mounting it - there should be no point at which the property line is less than 50 feet from that point. If the tower should happen to come down, it should land entirely on your property.

 

[kb2vxa]

Hi Box and all,

One thing these guys never noticed is the word "torch" which tells me the base plate is missing. I strongly suggest you get one and weld it on so you can set it atop the anchor bolts you'll set in the buried concrete base.

A free standing tower has tapered sections, that is they get smaller in steps one atop the other. A guyed tower is straight and if yours is straight GUY IT and I don't mean maybe. If you bracket it to the wall of the house what's the sense in having a tower? If you bracket it to the chimney you won't have a tower OR a chimney.

Most town ordinances prohibit the height to exceed the distance from the base to the property line for good reason. I would set it back from any structure on the property likewise for that very same reason but if you can't you take your chances the same as with a tree crashing through your roof. Well, that's what homeowner's insurance is for. MOST importantly make ABSOLUTELY sure it cannot fall across power lines!!!

When all is said and done, if you don't think Kong can climb it safely don't put it up in the first place. Nope, I'm not making a funny, it should hold you without undue shudder even if you weigh 300lbs. Take it from the Jersey Shore know-how, our winter gales are legendary and we take NO chances.

 

[W4KRR]

A free standing tower has tapered sections, that is they get smaller in steps one atop the other. A guyed tower is straight and if yours is straight GUY IT and I don't mean maybe. If you bracket it to the wall of the house what's the sense in having a tower? If you bracket it to the chimney you won't have a tower OR a chimney.

I agree with most of what you said, however, assuming it's a Rohn tower, Rohn's own specs say you can have up to like 40 to 50 feet of their 25G straight sections freestanding if you have a large enough concrete base. This isn't to say that a guyed tower wouldn't be safer or more sturdy, just that Rohn says it's possible.

 

[jhooten]

All you need can be found here:

http://www.rohnnet.com/ROHNNET/rohnnet2004/html2004/index.html

 

[BoxAlarm187]

Many, many thanks for all of the information. I will have to do some further inspection of the tower to ensure that it IS structually sound ... if not, I'll have to go shopping for a new one after the holidays.

I'll let y'all know if I make any progess with this!

 

[kb2vxa]

Well, if it's not structurally sound donate it to the Mythbusters and suggest you found it at Roswell. Then they load the thing with propellant and launch it with Buster seated at the old radio you said was a control panel. Hey, since they launced a pipe filled with parafin I'm convinced they can launch or at least blow up anything.

 

[kc8unj]

Well, if it's not structurally sound donate it to the Mythbusters and suggest you found it at Roswell. Then they load the thing with propellant and launch it with Buster seated at the old radio you said was a control panel. Hey, since they launced a pipe filled with parafin I'm convinced they can launch or at least blow up anything.

Haha yeah those guys pretty much just like to blow stuff up, whether they're actually busting a myth or not