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Author Topic: Channel Master 30ft mast  (Read 524 times)
KA5N
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Posts: 4380




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« on: July 09, 2004, 04:34:20 PM »

Having put up a lot of "push up poles" as we called telescoping masts when I was younger I know a bit about them.  You certainly can't just put them in a bucket of concrete and stand them up as a self-supporting mast.  They should be guyed every ten feet at three directions spaced 120 degrees apart.  The base can be set in a hole in the ground or over a pipe or rod driven into the ground or on the peak of a roof with a roof mount.  Two people can handle an installation quite well.  One person can install one if the wind is not too strong and he is EXPERIENCED!!! While you might get by with shortcuts for awhile sooner or later a strong wind will test your installation.  These masts are heavy and the longer the heavier!  You certainly don't extend them on the ground and then lever them up with the antennas in place.  An easy type installation is to brace them against a house or building at about the ten foot level.  Working on a ladder the topmost section (smallest) is pulled out slightly and the rotator and antenna is mounted and guy wires are attached to each section.  You leave a surplus of guy wire to be tied off later.  Then you grip the section and pull it upward (after releasing the clamp).  This section is fully extended by pulling it slowly upwards.  Notice that you have to be able to lift the antennas, rotator, and the mast sections with one hand while holding down the rest of the assembly.  When you have lifted up about a foot you grab the mastlower down  with the other hand and again pull the section up.  Leather gloves come in handy.  When each section is fully extended the clamp is tightened and a cotter pin inserted to lock the section in place.  Repeat  until all sections are extended.  Next tie off the guy wires one section at a time making sure that the mast is vertical and not bowed one way or another.  Check with the ARRL's Antenna Handbook about how to properly guy antennas.
Above all be careful.  Don't attempt an installation when the wind is up or in uncertain weather.  Extra help can make this job easier.
Good Luck Allen
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AA0NI
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Posts: 12




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« Reply #1 on: July 09, 2004, 03:28:53 PM »

I'm thinking about putting up a Channel Master telescoping 30ft mast in the back yard next to the house to support an 88 ft doublet. Has anyone had previous experience with this type of mast. It looks like it is going to have to be guyed for a permanent installation.

If I mounted it in a bucket of cement, could it be used without guys on a temporary basis (i.e. <20 mph winds).

Thanks for your advice...

- Daniel/AA0NI
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KD5JFT
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Posts: 82




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« Reply #2 on: July 09, 2004, 03:40:05 PM »

I have one up at my house.  The bottom is in a hole in the ground, no cement (I was very lazy and it was a "test/temporary" installation; up about 4 months now).  It is bracketed to the side of the house (extra reinforcement-several 2x4's) at about 11ft and again at 16ft.  It is guyed at the 20ft level.  It currently has several antennas on it.  1 vertical, one 6 meter loop, one 2M loop.  It has survived one tornado that removed a large portion of the roof from my next door neighbor's house!!!  I have been impressed by it's stability.  It has done much better than I expected.  I still consider this a "temporary" installation, as I now want one of their 50ft masts.

KD5JFT
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AA0NI
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« Reply #3 on: July 09, 2004, 03:58:57 PM »

Thanks for the reply. Have you located a source for their taller masts? Looking online, I can find a couple sources for their 30 ft masts, and maybe one dish provider with their 40 ft mast for $200-$300(!!!). I would probably buy four 10ft sections of mast and guy them off at 2-3 points for $60 before I paid what they were asking for the 40 ft telescoping mast.

Once you have your mast up - is it easy to lower it? Do you have to use a ladder to lower the sections, or would it be better to tip it over on its side before compressing the sections together? How well did it stay 'straight' up before you guyed it?

I'm in a single story home, so I wouldn't be able to attach it to the house much higher than 15 feet up - and that would be very close to the side of my property ... making it very difficult to guy it on 3 sides.

My plans include painting it flat black and raising and lowering the mast as I need to - usually in the evenings. I'm hoping that it is stable enough without guys to stand upright with about 50-100 pounds of concrete holding it up at the base. All that it will support in the air will be wire antennas.

Thanks again for any info.

73,
Daniel / AA0NI
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K0RFD
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« Reply #4 on: July 09, 2004, 04:52:42 PM »

I think this might be similar to the Radio Shack telescoping mast which I have seen described alternately as 36 feet or 40 feet.  I think it's 4 ten-foot sections, but when extended there's only 9 feet or so that comes out of the previous section.  I have one, guyed in 3 places with UV resistant dacron rope and thimbles I bought from The Wireman.  After a couple of weeks of adjusting the turnbuckles while the rope stretched in, it has been REMARKABLY stable. In some fairly intense windstorms, too.  Your doublet will guy it a little, but it still needs to be guyed every section or it will eventually bend, not telescope, and become useless.  It's a great mast though.  I have an A-99 on top of mine, and a standoff with a pulley that holds my 75-40-20 Umbrella (er, Fan) dipole.  The base sets in a piece of 3" galvanized pipe that's screwed into a floor flange bolted to a concrete patio slab.  It's bolted into the garage rafters with some pipe strap right about at 12 feet, so I could eliminate guys at the 10-foot mark. I have to loosen the bolts to take it all the way down.  If it ever falls down, it will probably crack the slab and take off the garage fascia board, so I'm pretty careful to maintain the guys properly.  Every once in a while I have thought about loading it as a vertical, but for now I haven't done that yet.  No good place for radials.

Just be sure you look at your property from every angle and find a place to put it where it CAN be guyed.  It needs to be.  Don't guy it so close to the base and so tight that you put a lot of downforce on it.  That will bend it too, eventually.  Don't put anything too heavy on it, or something with too much wind loading.  And you need to check the guys periodically.  Don't leave anything to chance.  If you take care of it, it will take care of you.  
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WB2WIK
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« Reply #5 on: July 09, 2004, 05:04:41 PM »

You need more than 100 lbs of cement at its base for it to self-support, even holding nothing at all (not even the wire antenna).  

The 30' mast weighs about 30 lbs.  If it is absolutely, perfectly 100% vertical and not even one degree off vertical, it might self-support in a gentle breeze.  Not in a strong wind.  But if it's just slightly off vertical, which is beyond your control if you don't guy it, it will simply lean and fall over in the direction of the lean as soon as you walk away from and stop holding it.  No reason it shouldn't.

Now, if you have that 100-lb "base" spread out over a large diameter circle, such as the cement piers that often support large round patio tables (and have a diameter of four to five feet), that's another story: That design will support the mast much better if it tries to lean slightly.  But that still would not be sufficient in a wind, where the 30' length of the mast, weighing about one pound per foot average, will exert hundreds of pounds of side thrust to its base in a 30 mph wind.

These were not intended (or designed) to be self-supporting for more time than it takes to tension guy lines.  That's about five, if you're slow about it.

You can make the 30' "slip-up" *more* self-supporting if you dig a 4' deep hole in the ground (post hole digger), plant a 10' mast in the center of that hole (perfectly vertically), surround that with stones and a couple of bags of redi-mix concrete and let that set, an now have a 6' long pipe emerging from the ground, permanently anchored in the earth -- and then, you "set" the bottom section of the 30' telescoping mast over that.  Now, that cemented-in mast will extend six feet up inside the 30' mast and stabilize it a great deal.

Under those conditions, the thirty footer probably can self-support, even with a wire antenna attached, and even in a reasonable wind, providing the wire is a fairly balanced load that isn't trying hard to pull the mast over in one direction.

WB2WIK/6





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K0RFD
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Posts: 1368




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« Reply #6 on: July 09, 2004, 05:11:40 PM »

By the way, you said you were having a hard time finding anything longer.  There's a fellow on E-Bay who advertises brand-new Rohn H-40 push-up poles (same as what Radio Shack used to sell) for $53.  That's a pretty good deal.
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KA5N
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Posts: 4380




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« Reply #7 on: July 09, 2004, 07:31:11 PM »

Something I forgot in my earlier post (which somehow got stuck at the front of the topic) is that you said you were going to paint the telescoping mast.  I would approach that with a great deal of caution.  The fit between the sections is pretty close (and varies from brand to brand)and a thick coat of paint may jam the mast so that it is difficult or impossible to lower.  I have had this happen on unpainted masts that have been installed a long time and have had to pull the sections back down instead of letting them slide down.  After you have raised and lowered the mast a few times, you will be an expert but I don't think you would want to do this on a daily basis.
Allen
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K1CJS
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« Reply #8 on: July 09, 2004, 09:08:42 PM »

Just a note of caution.  There are push up masts and then there are push up masts.  Some are a lot more sturdy than others.  A mast designed to support a TV antenna may not hold up any but the smallest amateur antenna.  

Pay the extra and get quality--it will be worth it to you and your home in the long run!
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N6AJR
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« Reply #9 on: July 12, 2004, 02:57:07 AM »

the 40 foot radio shack is out of production but can be found at some stores at $50 each and they are made by Rohn. have them do a local search and buy a couple extra.  I push mine into the dirt a foot or more, and guy the first 10 feet first, add antennas and extra long guys and push up the top, pin and bolt, then the next and pin and bolt, etc then guy the guys all off tight.  use insulators in the guys ( at least the top set) and I usually secure to the eve of the house at about 20 feet with an eve mount into the rafter tails.
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KT8K
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Posts: 1490




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« Reply #10 on: July 12, 2004, 01:36:37 PM »

This mast must be supported no less than 10' below the top, even with just wire antennas, and don't expect to tilt a telescoping mast up or down with it extended at all.  Also, putting it up just when you want to use it will become tiresome pretty quickly.  Look around and see if someone has a commercial telescoping mast that is DESIGNED to be free standing, and that they want to get rid of.  

One of the hams in my club found a homeowner who had bought a house with a beautiful 55 foot telescoping mast with a winch to raise and lower it.  The new homeowner just wanted it removed.  It was a big job taking it down, but he is now able to put it up at his own house (with the appropriate concrete base, grounding provisions, etc.) and it will be great.  An electric winch option is available for remotely raising and lowering it (excellent in the Winter or bad weather) and it has a second winch to tilt it over for maintenance.  Ask around and keep your eyes open - you may be able to find a deal like this.

Telescoping masts such as you describe are great for Field Day, but require a bit more engineering for permanent use and are NOT easy to put up and take down.  Also, do not depend on the clamps to keep it up forever - they can vibrate loose, and they will rust.  The masts we use for Field Day had a propensity for deciding to come down all at once during takedown, nearly beaning club members on a couple of occasions, before we got smart and a mechanically-astute club member rebuilt them with cotter pins and new clamps.

Be safe, and good luck.  73 de kt8k - Tim
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WB6BYU
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« Reply #11 on: July 12, 2004, 04:45:53 PM »

One way to make a mast more self-supporting and easier
for one person to install:  dig a hole 5' deep and
insert a length of pipe LARGER than the base of the
push-up mast (preferably a fairly snug fit).  Slip the
base of the mast inside this pipe to help level it,
then secure the base pipe with concrete/rock/dirt, etc.
The push-up mast should be removable from the socket
when you are done.

To install, slip the push-up mast into the socket.  Now
the push-up point is only 5' above the ground, and a
short step-ladder probably will be enough to install
antennas and push it up.  But I still wouldn't count on
it to hold more than a wire dipole or a 2m groundplane
through a good windstorm.  Of course, the top of the
mast is 5' lower than if it were setting on the ground.
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