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Author Topic: Rotating the whole mast.  (Read 3060 times)
AA9G
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Posts: 94




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« on: June 06, 2013, 08:56:25 AM »

Hello all,
Going with a guyed 30' Rohn push up with a Hexx on top. Have seen people discuss placing the rotator at or near the bottom so that the whole thing rotates. How is this done and what equipment do I need to get? 73, David
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WB2WIK
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« Reply #1 on: June 06, 2013, 09:41:26 AM »

It's pretty easy, actually.  The Rohn H30 uses floating guy rings for guying, so the mast can rotate within them even once it's guyed.  

The trick is to make certain the mast is perfectly vertical and balanced, with equalized guying tension so it stays that way when it's rotating (and doesn't bind).

I've done this by simply bolting a rotator plate an inch or two above the cement pad (make sure that's perfectly level also) onto the pad using embedded j-bolts, then mounting the rotator on that plate and assembling the retracted mast onto the rotator (it really helps to have friends helping with this, so they can attach the lower set of guys during this process, and tension those guys while using a level on the mast).

Not difficult.  A HAM-IV or G-800SA or similar will do this job.
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KA9O
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« Reply #2 on: June 06, 2013, 04:24:11 PM »

Go to Yahoo Hexbeam group . Tons of info and pictures.
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WA8FOZ
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Posts: 194




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« Reply #3 on: June 06, 2013, 09:44:07 PM »

Go for it!

I have done this a number of times. I have mounted the rotor inside a small tripod at ground level directly under the eaves and attached a collar ( a piece of pipe with I.D. slightly wider than the mast) to the edge of the eave, and pushed the mast up through it. For a light yagi, I have used 10-foot steel TV mast sections fed through the collar. If you do this, make sure the sections are pinned together in some way to prevent twisting - the notch on the mast will not be strong enough to stop the sections from turning.

After you put your mast through the collar, the antenna goes on it. Then you add as much more mast as you wish from the bottom; and you place floating guy rings every 10 feet or so.

This strikes me as more durable than a big, heavy rotor on top of a push-up mast. In any case, when I did it it worked fine and held up through many Michigan thunderstorms.
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K2MK
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« Reply #4 on: June 07, 2013, 05:24:24 AM »

Pushing up a Rohn H30 with a hex beam on top is a bit of a challenge. Adding a rotator ain't gonna make it any easier. Rotating the entire mast is indeed an excellent option.

As already suggested, go to the Yahoo Hex Beam group and look at all of the postings in the Photo section. Lots of examples of rotating masts.
http://groups.yahoo.com/group/hex-beam/

Also look at K4KIO's page for the basic illustration of a rotator and thrust bearing on a 4x4 post:
http://leoshoemaker.com/hexbeambyk4kio/broadhexmast.html

Another method (albeit more expensive) is described in the files section of the Yahoo group. Look for "Rohn H30 in BAS25G Section".

The Yaesu G-450A is very popular with Hex beam users as is the GS-050 or GS-065 thrust bearing. Used in conjunction with a 4x4 post it is a very solid arrangement. The Rohn H30 (and also the 9H50) are very popular and there are some useful help files in the Files section of the Yahoo group. It is also very important to observe the manufacturer's guying recommendations.

73,
Mike K2MK
« Last Edit: June 07, 2013, 05:39:45 AM by K2MK » Logged
AA9G
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Posts: 94




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« Reply #5 on: June 07, 2013, 09:08:25 AM »

Nice setup Mike, thanks for pointing it out. Tell me, what kind of fertilizer does Lowes sell that makes coax magically sprout from the ground? I sure didnt see any signs of trench digging.  Grin
And I sympathize with your XYL issues. Makes me glad I don't have one and any future XYL will have to understand that me and my antenna farm are a package deal!
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K2MK
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Posts: 407




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« Reply #6 on: June 07, 2013, 09:25:43 AM »

It's an optical illusion. The coax and rotor cable are direct burial and are just an inch under the surface. I dug out a slot at the antenna location and inserted a PVC conduit elbow (plus a short length of straight conduit) for protection against weed whackers. That's why I also don't worry about water entering the top of the conduit. It just runs out the other end directly into the soil.

73,
Mike K2MK
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AA9G
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« Reply #7 on: June 12, 2013, 12:14:39 PM »

Hi Mike,
Looking through the yahoo group I see you suffered a mast failure 2 years ago. Then you came up with the new install in August 2011 and those are the pics you posted in the BASG25 file?
I'm asking cause I want to know if you ever determined guying failure as the positive cause for the failure?
Have you found using only the rebar base to be stable over time? I really hope its worked for you because pouring concrete and digging huge holes is really not something I want to do.
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KA5N
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« Reply #8 on: June 12, 2013, 12:33:00 PM »

Mount the mast on a 12 ft 4X4 with the lower end about 3 feet into the ground
a couple of forty lb. bags of concrete are enough to stabilize.  Mount the rotor on
a shelve about a foot up from ground, add a trust bearing near the top of the  4X4
guy the mast securely using at least three guys (dacron with uv wrap is great)
6 foot 4x4s are good anchors.  A strong person can pull the mast sections out, a
not very strong person can lever the mast up a couple of feet at a time by using a
metal ring held in place with a hose clamp.  You have to lock the mast and move the
clamp and ring and then lever angain.  Sounds awkard but is pretty easy.  To lower
the mast, gravity will do all the work.  You just do the levering in reverse.
Watch out for high winds.
Allen KA5N
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K2MK
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Posts: 407




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« Reply #9 on: June 12, 2013, 12:55:26 PM »

As KA5N has just posted, installing a rotating mast on a 4x4 post is surprisingly easy. Yes you need a manual post hole digger and yes you'll need 1 or 2 bags of post-hole cement but it's still a one man job. In the grand scheme of using a Rohn push-up mast it takes far more effort to push up the mast then it does to assemble the 4x4 post.

My first install was close to the house. Originally I used all 3 sections of the H30 mast but only extended the top section about 4 feet. My concern was that my guys were not optimum. Two of the guy anchors were too close to the mast and one of the guy anchors was two far from the mast. Further, the angle between the guy anchors was not uniformly 120 degrees. But everything went well and after about a year I got cocky and extended the mast fully. Too keep the mast from swaying excessively I had the guys from the two close anchors really tight. This should have been my red flag. In a moderate wind the mast buckled just above the first joint. The guys never failed but I believe the excessive downward force from the tight guys led to the failure.

When I finally got permission from the XYL to move the antenna further out into the yard to permit a proper guying arrangement she insisted that the 4x4 post was out of the question. Hence the more deluxe arrangement with the BAS25G. This arrangement is completely stable. It has not moved an inch in 2 years. This includes 1 earthquake and lots of high wind events. Although I did lower the mast to 10 feet for hurricane Sandy.

73,
Mike K2MK
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AA9G
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Posts: 94




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« Reply #10 on: June 12, 2013, 04:32:43 PM »

Thank you Mike and Allen for the excellent info. I never knew about post hole cement before. Great stuff. One more question. In my research I came across a reference to some nifty little critter that's supposed to make rope guy rope adjustment and cinching a snap but I now cannot recall what it was. Any ideas?
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K2MK
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Posts: 407




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« Reply #11 on: June 12, 2013, 05:03:27 PM »

You're probably thinking of guy rope tensioners. They are available from a couple of ham suppliers:
http://hamcall.net/linegrip.htm
http://www.qsradio.com/

I use them with 3/16" diameter line and they work very well. Once everything is adjusted I then use a screw down type clamp as a backup.

I've also looked at Penninger's guy clamp block. It almost seems too simple.
http://www.penningerradio.com/gallery.asp?id=31&cc=

73,
Mike K2MK
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AA9G
Member

Posts: 94




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« Reply #12 on: June 12, 2013, 06:51:49 PM »

Ahh yes thank you. Its one of the first two for sure.  I think the buck model. Is there a specific screw down clamp made for rope or will a normal one work?
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K2MK
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Posts: 407




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« Reply #13 on: June 13, 2013, 04:09:10 AM »

The most common clamp is the saddle clamp. I buy Crosby brand from McMaster Carr. Part number 3465T12. The zinc plated version is just fine, these clamps are seriously corrosion resistant. Other brands that you might find at Home Depot and Lowes might not be of the same quality as the Crosby and could rust. If saddle clamps are your only clamping device you should always use two. If it's a backup to a spring tensioner one might be adequate.

I also like the McMaster Carr 5513T14 low profile clamp. Saddle clamps really crush the rope and I often wonder if the crushing breaks some of the fibers. These low profile clamps apply a uniform pressure and hold just as well as the saddle clamps. Since they are stainless I add a dab of anti-seize to the threads to prevent galling. The nuts are metric and will require a 10mm nut driver.

http://www.mcmaster.com/#

73,
Mike K2MK
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AA9G
Member

Posts: 94




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« Reply #14 on: June 14, 2013, 02:26:16 PM »

Funny you mention Lowes. I was just there looking for rope and discovered they sell what appears to be the same line grip Buxx has for only $3.  Shocked
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