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Author Topic: First Time Tower Raising - Longish  (Read 755 times)
NZ4DX
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Posts: 1




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« on: November 22, 2001, 09:48:00 AM »

Gentlemen (and Ladys),
I finally have my own house and am in the process of figuring out a permanent tower arrangement.  Since this is my first tower raising I figured I better ask the experts before I get to far in to it.

I've been looking at a Universal tower between 30 and 50 foot.  My first antenna will be a cushcraft A3S, which has a 4.4 Sq Ft wind load.  First question, should I build in some 'extra load' as a safety margin and future growth?  I'll probably only have the one beam. I live in the Denver area, which is subject to some very strong winds.  Another question.  How high above the house should the beam be?  I live in a two story house. It looks like a 30' tower will place the beam at about the same height as the top of the roof.

About the base, how hard is it to mix and pour the concrete myself?  How long should the concrete cure before putting the tower up?  Do I put the tower up with the beam already attached?  Or do I have to climb up and install it afterwards?  If I climb the tower, will it hold me (230lbs), plus the beam as I work?

As you can see I have lots of questions.  Your input is greatly appreciated in advance.

Thanks,
Dana
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KL7IPV
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Posts: 984




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« Reply #1 on: November 24, 2001, 01:09:39 AM »

I lived in Colorado Springs for 15 years and used a Tri-Ex W51 tower there. It survived 80MPH+ winds, not to mention the freezing, heat and an ice storm or two. The tower when collapsed will support you when working on it, in fact there is a platform made for a person to stand on to do antenna work. The platform bolts to the lower unmoveable section of tower. I kept my tower at a level that had my antennas up about 40 feet and worked anything I could hear and I NEVER ran over 100 watts.  Buy pre-mixed concrete and have it poured. You will need 3 1/2 yards at least and it is more cost effective to buy it. Be sure you have the proper base and steel for the tower. My tower is rated for about 9 sq. feet of antennas in the air at 50 MPH winds and I haven't reached that loading yet. If the tower is supported additionally with house brackets, that figure is higher but I do not know how much. I have an Explorer 14 beam and some smaller 2 meter stuff. Together they are about 8 Sg. feet of antennas. I use a Hy-Gain Ham IV rotor. The tower will support lots of standing dead weight but is limited to 150 pounds when lifted off the stops. NEVER climb a tower unless completely lowered to the stops. I used the same brand and model tower in Anchorage with a TH3JR and it survived anything that came it's way there too. Check with Texas Towers for more info, they can more than likely supply all you need along with good information. Check the Jefferson County and Denver City ordinances for any permits you will need. If you are in Arapahoe or some other county they will differ. Also check to be sure you aren't covered by CC&Rs in the community where you live. I am using the same tower, rotor and antennas here in Las Vegas now and it still functions as it did when it was new in Colorado in 1983. Be sure to follow ALL the instructions that come with each component BEFORE and AS you install it. Good luck.
73
Frank
KL7IPV
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WB2WIK
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Posts: 20561




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« Reply #2 on: November 26, 2001, 12:34:28 PM »

Always build in some "extra load" margin, of course.  The A3S 4.4 sf wind load rating is for only the beam, and does not include the mast it's mounted on, or the coax hanging from it, and other things that will additionally load your tower.  

You'll want the A3S to be at least 45 feet above ground in order to fully function; at only 30 feet, it sounds like it will crash into your roof (!), but beyond that, it won't have much of a pattern, especially on 20 meters, because ground reflections will be quite severe.  65-70 feet is an ideal height for a 20 meter beam, to minimize this problem.  If you can't go that high, then I'd opt for 45 feet as the next best height.

As Frank said, it's normally more economical to call a cement yard and have them deliver the concrete.  Tell them it's for a tower base, and you'll need construction grade concrete aggregate, and they'll know exactly what you mean.  The cement trucks normally hold 10 yards, and you'll need less than half a load, so they'll probably want to schedule you towards the end of the day.

I wouldn't install the tower with the beam already on it -- too many things to go wrong, unless you have a very strong tower that is specifically designed for a "tilt-over" function.  Any tower capable of handling the antenna and rotor with ice loading and strong winds will obviously also hold you.  230 lbs is not much of an added load.  I'm 170 lbs and when I climb my tower (often), it doesn't move even 1/32".  Actually, it doesn't move at all.  I doubt the tower knows I'm on it, but it's a steel tower that weighs a whole lot more than I do.  However, with aluminum towers, I'd probably be more careful to follow the manufacturer's advice.

If you live in an area with "zoning," that is, building ordinances that control construction, you may well need a permit to erect a tower.  If so, I'd apply for that first and see what the requirements are; otherwise, you may find yourself with a perfectly installed tower that wasn't properly documented so will have to be torn down.  The tower manufacturers' recommendations for anchorage/footing may or may not be acceptable in your community.  I know of at least one case locally (Ventura County, CA) where they couldn't care less what the tower manufacturer recommends, they have their own concrete requirements for tower bases that go way above and beyond reason...they would have you install a 50' tall amateur tower as though it were a bridge intended for truck traffic.  No joke.

73 de Steve WB2WIK/6
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WA4DOU
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Posts: 436




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« Reply #3 on: November 29, 2001, 10:59:48 AM »

I'd strongly advise that you spend at least a month or 2 and weigh all the options, in addition to carefully studying the manufacturers technical data. Will you really be happy with the 4.4 sq. ft. windload trapped yagi or will that merely wet your appetite for more? Do you already have the antenna or is it remaining to be purchased? If you decide to upgrade to a larger antenna, will you still have the safety margin you need to do it on this tower? And will you have enough rotator to safely accomodate it? Above all, subscribe to towertalk and any other "tower"/"antenna" lists and study their archives. Don't take any shortcuts and contact Champion Radio about their free booklet "The Ten Most Common Tower Building Mistakes". Their ads are in the back of CQ.
  You want to have thought this thing out carefully and completely. If you don't you may not wind up with a safe installation, or one you'll be completely satisfied with. 30- ft. isn't high enough for the 20 and 17 meter bands. If you can be satisfied with 15 meters and above, yes. 45-55 ft. is the range you want to shoot for, or higher, if possible.
  I followed the proceedures I outlined to you about 2-1/2 years ago and am thoroughly satisfied with mine. Its 52 ft. high and built to withstand hurricane force winds exceeding 110 mph. Proceed with caution, stop at any point you see things not going well, correct the problem, no matter how long it takes.
  Commercial concrete is the way to go, don't rush it, let it cure properly. Even try to learn all you can about concrete. Make sure you get all the tower you really want the first time and don't overload it. Leave a margin of safety. I personally wouldn't put 9 sq. ft. of windloading on a 9 sq. ft. rated tower.
  Good luck, it isn't something to rush into ! 73 Roy
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INITZERO
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Posts: 102


WWW

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« Reply #4 on: November 29, 2001, 03:54:14 PM »

> contact Champion Radio about their free booklet
> "The Ten Most Common Tower Building Mistakes".

That publication can be found here...

http://www.championradio.com/10mistk1.pdf

Matt (k4mls)
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KL7IPV
Member

Posts: 984




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« Reply #5 on: November 30, 2001, 02:29:01 AM »

As was mentioned early on, check the local ordinances too. My tower base was required to be only 3 ft sq by 4 Ft deep by Tri-Ex. The zoning people here had me put in a 3 ft sq by 5 ft deep base. 3200 POUNDS!! of concrete and the tower weighs 358 pounds. It takes a month for concrete to be ready for use for the tower. Let it cure at least that long. The aggregate required was 5500 pound construction grade as well. It cost me $331 delivered and the concrete delivery guys did the work of pouring and carrying to the hole in the backyard. The tower base and specs are not a place you want to scrimp and save. Do it right and if it seems "overbuilt", even better for you in the long run. Good luck.  
73
Frank
KL7IPV
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K6RAS
Member

Posts: 78




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« Reply #6 on: December 05, 2001, 06:36:07 PM »

Only thing I  might ad is the age old advice that you'll find in every issue ot QST.  Rohn antennas spends some good money to publish their "WARNING" ad in QST; it's more than a quarter page of space that offers advice and never once makes a sales pitch.  Pick up a copy and read what they have to say.  Your money will be well spent cuz you'll get good advice and QST will increase circulation.  It's a win/win all 'round.
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K9KUZ
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Posts: 19




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« Reply #7 on: December 05, 2001, 09:06:32 PM »

My simplest all around installation features a self supported light duty 48' tower that is bracketed against the house as high up as possible.  This worked great for me for many Illinois prairie years.  Antenna was a Mosley TA-33.  The tower was a very old tv type, tapered, with house bracket at 25'.  Dug 3 holes with post hole digger, 3' deep, etc.  Simple, sweet, cheap.
Best advice:  locate at least 3 towers in your area, and ask the owners all of your questions.  
((I now have 100' of Rohn 45, also at a new house!))
PS: if you can get a copy of the ROHN catalog it will serve you well with many specs, even for other mfgrs.

Jim
K9KUZ@arrl.net


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N4ZFQ
Member

Posts: 13




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« Reply #8 on: March 14, 2002, 12:41:39 PM »

Dana,

 Please keep in mind that towers are great things but safety must be your top priority!!! If you are not sure about something, ASK. You may save your own life.
 If you purchase a crank up tower, remember to lower it to it's lowest point before climbing. This is true with any structure that can be raised and lowered. One more point. When working on a tower, the man in the air is in charge. It's his butt hanging in the air and you don't need a large crew of know-it-alls on the ground trying to run things that effect the mans safety on the tower. You can accomplish more with less help. Trust me, I've been there. When someone starts yanking on a guy wire on the ground and you are 150' up on the tower, who do you think feels the most movement??? Get the point. Select your crew carefully.

Good luck and enjoy your project.

Colin   N4ZFQ
Ft. Defiance Va.
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