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Author Topic: 30 ft freestanding masts??  (Read 3856 times)
WB7TDG
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Posts: 69




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« on: July 02, 2012, 04:43:16 PM »

What I want to do is put up 4 to 5 30 ft freestanding (unguyed) masts.
We have horses at this qth and them critters and guy lines don't jive too well at times...hence freestanding.
What I am planning to do is sink either 4 by 6 or 6 by 6 12 ft long pressure treated posts in the ground at this qth with 3-4 80 lb bags concrete mix per mast, 3 ft in the ground, with about 3 inches above ground to compensate for winter snow and rain...to keep the water from rotting out the posts.
I plan on making each mast out of laminated 16 ft 2 by 4 stud lumber..some hand picked stuff that is relatively decent...then will glue and bolt them together to make 30 ft antenna masts.
Each mast will tilt over at the top of the pressure treated posts.
The price of making the masts and supports out of thick walled galvinized pipe is getting way to expenise at this time to consider...
The antenna is a horizontal loop, up 30 ft about 280 ft in 4 sided configurating.
comments(constructive) anyone?
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N4JTE
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Posts: 1155




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« Reply #1 on: July 02, 2012, 05:52:13 PM »

A couple of thoughts after having done many of these and taller for various vertical experiments. If you posthole the holes one 80lb bag of cement is plenty unless you are in sand. A 4x4 pt 12 ft will last for many years if you seal the bottom, and set  below your frost level. Two 16 ft 2x4's with a two foot lap should get you to 30 plus feet. I would stiff back the bottom two by four. A couple of 3/4in thru bolts will be sufficent and removal of top one will allow tilt over, albeit a little heavy.
Lastly, I would not expect amaxing results with a loop that low but we all do what we can with existing constraints.
Good luck,
Bob
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WB7TDG
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Posts: 69




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« Reply #2 on: July 02, 2012, 06:15:30 PM »

thanks om...the county zoning athourity says I can have...drumn roll...stuff to 80 ft topsfer antennas on one structure...this is above 30 ft..
below 30 ft is anyones guess..
So I am completating 30 ft masts.....
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WB6BYU
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Posts: 13126




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« Reply #3 on: July 02, 2012, 06:52:50 PM »

I'd consider looking for the 40' (actually 36') TV push-up masts.  Tilt it up into place
then telescope it up to full height one section at a time.  Much less stress on the mast
that way than trying to tilt up a complete mast.

I have one out back right now attached to a 5" diameter upright on one end of a grape
arbor.  I used a couple of chain link fence brackets with lag screws through them to
secure it.

Another option is 40' lengths of irrigation pipe - especially after one end gets run over
by a tractor.

Make sure your support post is rugged - it may become a favorite backscratcher.

If you are going to tilt it over, make the pivot point as high as possible off the ground,
as that reduces the forces required.

You might end up wanting a back stay to counteract the pull of the antenna.

Plant the posts further apart than your antenna corners - at least 80'.  Put a pulley and
halyard on each and use that to secure the antenna.  That makes it much easier to
change the antenna out for maintenance or to try something else.
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ZL1BBW
Member

Posts: 370




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« Reply #4 on: July 02, 2012, 10:35:33 PM »

Kia Ora from ZL, if you get the posts driven in, dig our a square how ever deep you can, and then get the post driven in with a post banger, that will make it tight as, put a couple of 6x2 crosses on the base of the mast underground, then pour the concrete round the top, that will help increase the ground resistance at the top of the post.

This is how we put in strainer posts in soft ground, or use building blocks to give the post something hard to push against.

Go for 6 x 6 if you can, we use H4 level of treatment minimum, ddont know if you go by that standard.

If the post is cut, put that end up, and soak (if you can) the bottom bit in old engine old and copper wood preserver mix.
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ex MN Radio Officer, Portishead Radio GKA, BT Radio Amateur Morse Tester.  Licensed as G3YCP ZL1DAB, now taken over my father (sk) call as ZL1BBW.
W8JX
Member

Posts: 5604




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« Reply #5 on: July 03, 2012, 05:32:17 AM »

What I want to do is put up 4 to 5 30 ft freestanding (unguyed) masts.
We have horses at this qth and them critters and guy lines don't jive too well at times...hence freestanding.
What I am planning to do is sink either 4 by 6 or 6 by 6 12 ft long pressure treated posts in the ground at this qth with 3-4 80 lb bags concrete mix per mast, 3 ft in the ground, with about 3 inches above ground to compensate for winter snow and rain...to keep the water from rotting out the posts.
I plan on making each mast out of laminated 16 ft 2 by 4 stud lumber..some hand picked stuff that is relatively decent...then will glue and bolt them together to make 30 ft antenna masts.
Each mast will tilt over at the top of the pressure treated posts.
The price of making the masts and supports out of thick walled galvinized pipe is getting way to expenise at this time to consider...
The antenna is a horizontal loop, up 30 ft about 280 ft in 4 sided configurating.
comments(constructive) anyone?

Here is my take on it. First, forget the cement. Bad idea here. Many use cement as a band-aid fix for not digging a proper hole for post. How many telephone poles do you see set in cement?? When that set a power pole they sink at least 15% of total length/height in ground, sometimes 20%. I would get some 20 or 22 foot 6x6's and post hole drill them about 5+ feet deep. Level them up and tamp dirt on them in with a spud bar. Over time the earth will grab and hold post better than cement around it which will tend to raise up and loosen with freeze cycles and when it does your have a problem. Many years ago my neighbor put up a fence used cement around wooden post. After many years some raised out of ground and some rotten in cement. A fence that I put up about same time with 6x6 post set 4 feet in ground is still straight and solid 25 years later. After you set your poles as above then attach a piece of heavy wall 20 foot metal water pipe to get your 30 feet.
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KL3HY
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Posts: 117




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« Reply #6 on: July 03, 2012, 10:34:38 AM »

I was going to bring up telephone poles as well.  Any reason why you wouldn't want to get some surplus telephone poles and use them?  It would be a little more expensive to sink them 5 ft. deep vs. treated lumber, but you'd get a little more height out of it.  They'd be a lot more durable too, and easier to use for other purposes (exterior lighting, etc.).

Mike
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AD6KA
Member

Posts: 2236




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« Reply #7 on: July 03, 2012, 10:21:12 PM »

Quote
Any reason why you wouldn't want to get some
 surplus telephone poles and use them?
 
I remember my old man telling me "way back when"
the phone company would come out and sink a telephone pole
(not "surplus" either) into your property for a fee.
As long as it didn't interfere with their equipment.

I imagine that with liability clauses and such
these days, they wouldn't go near an idea like that
with a 20 foot pole.

But it wouldn't hurt to check...or to befriend a
workcrew with beer & pizza. Stranger things
have happened....
Ken  AD6KA
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ZL1BBW
Member

Posts: 370




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« Reply #8 on: July 03, 2012, 11:47:08 PM »

My Dad now SK ZL1BBW happened across the power co truck with a """surplus""" 2nd hand concrete power pole, whoosh, bang, Smiley a box of beer and there it was magically up and erected.

That was 30 odd years ago and it still stands today with a Telrex 3 ele 20M on top.

Only problem for me is I have to get the beam down to move it my QTH.
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ex MN Radio Officer, Portishead Radio GKA, BT Radio Amateur Morse Tester.  Licensed as G3YCP ZL1DAB, now taken over my father (sk) call as ZL1BBW.
K5KNE
Member

Posts: 65




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« Reply #9 on: July 04, 2012, 02:43:09 PM »

I would opt for the telephone poles in your situation.  What you propose may work fine, but it is not worth the materials and work needed to get the antenna up only 30' high.

I have had all sorts of antenna supports and antennas over 50+ years of being a ham. Some were really terrible. The utility of having fold over supports that you will seldom ever fold over is not worth the effort. A pole with a pully near the top will last a long time and be a lot easier to use. Be sure they run a ground wire from the top, down the pole and spiral coiled to the base of the pole - for lightning protection. I hope that you realize that the loop you propose to put up is also a big "lighting catcher" - so disconect your antenna when not using it.

A lot of utility companies use contractors to do the jobs they used to do with their own people. If you check around you might find one that has or is pulling some poles somewhere and will be reasonable to set them where you would like.  As a Civil Engineer, I would not plan on dreaming up a foundation or concrete setting of a pole or support without knowing more about the soil conditions etc.  If you do decide to do this - get some good advice.

Good luck on your project.

Walter  K5KNE

 
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