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Author Topic: Putting up a 40 foot TV mast  (Read 503 times)
KI6NDA
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Posts: 10




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« on: December 02, 2007, 05:31:58 PM »

Greetings,

Brand new General here.  Need some help please.  I have searched and still can't really find the best way to do this.  Perhaps I can find some sage advice here.

I have run string lines till I'm blue in the face, and have finally settled on the best location for an Inverted V dipole, fed with ladder line.  Now I need to plant that TV pole in the yard and git'er'done.  

My questions:

The mast will have to go on concrete (I have alot of it).  I can drill holes in the concrete for molly inserts to bolt down the mast.  Is this acceptable?

Guy points...  I have a few small trees, but I think I should do better.  Can I use metal fence posts driven deep?  How much could I leave exposed?  Or...?  This is a semi-permanent install.  I hope to get out of here some day.

For guys, I'm in a bit of a quandry.  I had planned to just use the 3/16 double weave dacron.  Then while talking with the neighbor (friendly and supportive) it occured to us how easy it would be for kids to cut it for some late nite jollys.  Bad neighborhood.  So now I'm thinking 6 strand 20 gauge for the bottom of each guy(about 15 feet), transitioned to dacron using egg insulators.  Tbis would take more effort to sabotage, and more likly to be ignored.  Question, do I need to break up the 15 foot length of metal guy wire with additional egg insulators?  These sections will all be at the bottom of the mast guying system.  But they are over 1/4 wavelength for 10 and 15 meters.

And, is 3/16 Dacron strong enough?  Nothing else is going on the mast.  Just the dipole center support.  I might add, the ladder line will be pulled (gently) away from the mast at 45* angle to a non metalic support in the yard.

Thank you in advance for any advice you can give.

73s de KI6NDA, Jerry
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NA0AA
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Posts: 1043




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« Reply #1 on: December 02, 2007, 06:41:05 PM »

Sounds like you are doing OK - the bolt is really only to keep the end of the pole from walking.

If you are using dipoles hung from the top, you don't have any problems with resonant guys per-se, what you have described should be OK to reduce the potential for vandalism.

Do put two pullies with independent halyards at the top of the mast, then you can raise and lower antenna w/out moving the mast - this is key to happiness with a mast.
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AB8XA
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Posts: 30




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« Reply #2 on: December 03, 2007, 04:16:21 AM »

If you want to make ground-terminated guy wires more visible to prevent people from running into them, you can use sailboat rigging covers.  They're slit white plastic tubes available in several sizes for different thickness rigging.  http://www.defender.com is probably the cheapest source.  Search on rigging cover.  If you use stainless steel rigging at the bottom of the guys, it will be VERY difficult for anyone to cut it.
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WW5AA
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Posts: 2088




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« Reply #3 on: December 03, 2007, 06:49:03 AM »

I would go for the trees if possible, the higher you can get the ends the better. An inverted "V" with the ends close to the ground has a lot of ground loss. Have fun!

73, de Lindy
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N3BIF
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Posts: 1190




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« Reply #4 on: December 03, 2007, 09:19:46 AM »

One trick is to use the elements of the v as the mast guys, kill two birds, as it were. Another trick is to run the Dacron to 10 feet or so above grade and splice in a chain or cable the last stretch which would be in reach of vandals.
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KI6NDA
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Posts: 10




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« Reply #5 on: December 03, 2007, 06:16:49 PM »

Thank you for the replies.

KG6WOU:  I'm pretty dince when it come to marine terms, but google is my friend.  From what I can find, a halyard is a generic term for a rope used for hoisting something.  And I'm guessing the double pulleys (with seperate halyards) are for having a backup if something causes the first to break.  If I'm wrong, please set me straight.  Thank you!

AB8XA:  That's a good tip.  I am on a shoe string budget, but the first time I run into one, I'll be looking for a low cost way to do the same thing.  Stainless cable would be nice, but I think costly.  I will look into prices, but it's going to be hard to beat 20 ga. TV guy wire.  I'm not expecting someone to plan to cut it.  I'm thinking of kids just pulling out a pocket knife and saying, "wanna see it fall, HE HE".  Thank you!

WW5AA:  The trees are small, and really more in the way.  I have to do some pretty good pruning just to do this.  My end supports are going to be 20 foot 4x4 posts, sunk 3-4 feet, then braced to existing wood fences.  Dipole will span my yard, from property line to property line.  No guys on the end supports possible.  That will give me 16 - 17 foot ends heights.  I really wanted to get those ends up 20 feet, but that will wait for later.  Perhaps some 20 foot, 3 inch PVC clamped to the posts.  Thank you Lindy!  This is going to be fun!

N3BIF:  As you may see in my reply to Lindy, I just don't have strong end supports.  But for the next QTH, I'll remember that tip.  I will look at something tougher for the bottom cable.  Thank you!

I really appreciate all the replies.  I priced the fence posts today.  About 6 bucks apiece.  I think I can do this!

73 de KI6NDA
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K1CJS
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Posts: 5879




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« Reply #6 on: December 06, 2007, 06:39:02 AM »

I had a forty foot mast up for quite a few years, but I didn't go quite as permanent as you plan.  No concrete, just a four foot length of 3/4 inch pipe with a couple of rods through it (at right angles) driven into the ground to keep the mast from sinking in and to keep the bottom from walking out.  It worked fine.  

I used regular TV guy wire (stranded aluminum) to support the mast, but the antenna was a vertical type with radials (2 mtr.) so I really didn't have the detuning problems usually found with wire guys.  If you use Dacron line from the top of the mast to a point ten of fifteen feet from the ends of the guy line then transition to wire, you probably won't have any interaction--unless you're running the antenna parallel to one of the guys.  Try to avoid doing that.

For safety (if it is a problem--you didn't actually say this), just get ten foot sections of white PVC pipe (Home Depot), one section for each guy wire and spray paint 'em orange.  Tie them to the guy wire with solid wire (drill one or two holes in the end of each pipe to do this) and you'll be good to go.  Of course, if the guy wires are out of harms way (no traffic area) you may not want to do this--it'll just draw attention to them.  Good luck!  
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NA0AA
Member

Posts: 1043




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« Reply #7 on: December 06, 2007, 09:48:32 AM »

Halyards are for hoisting your wire antenna to the top of the mast - I recommend two so you can hoist to antenna separately should you so need.  But as a spare works for me too - by the time you get this thing up and guyed, you won't want to lower it to adjust antenna.
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KD6IQS
Member

Posts: 3




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« Reply #8 on: December 30, 2007, 10:22:47 AM »

Hello,

I think I've done something similar to what you're trying.
I used a 5 gal paint bucket, put in a vertical copper pipe and then poured in quick drying cement around the copper pipe. This created a 60 lb. "anchor" base. This works very well for a  single pole 25' mast. Of course, I did have to bury this concrete block about half-way into the ground for stability.

I did this with no prior experience using concrete or cement. It turned out fine and works well. The only
thing I'd have done differently would have been to
use a bucket with a larger foot-print. The mast is a
1.5" steel antenna mast.

I did have to use mounting brackets to secure this
mast to the eave of the house. So far this installation
has survived several wind storms greater than 40 mph.

At the top of this mast is a Diamond BB7V vertical
antenna. Works great and I have worked Europe and elsewhere.

Good luck and I hope you find a solution.

73's de KD6IQS



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