Antenna sway

[VETCOMMS]

I just put up a Laird Antenna on about 20 feet of chain link fence top rail (2 pieces).   We had 27 mph winds today and i noticed a bit of sway in the upper pipe. 

Am I up too high above that upper bracket mounted to the building?  I'd think ice & snow will make that sway worse.

 

[WRXB215]

5 minutes ago, VETCOMMS said:

Am I up too high above that upper bracket mounted to the building?

I know some people use top rail for antenna masts but it is not engineered for that. You are asking a question that only a PE can answer. @SteveShannon is a PE but he is retired.

[WRYZ926]

I suggest using something like this EZ 43-A Adjustable 3 Way Down Guy Ring for up to 2-1/4" Mast - Heavy Duty placed right below the antenna. You can use some good Dakron rope such as 1/8 inch Black Dacron Polyester Cord for your guy rope. I like using Nite Ize CamJam Cord Tightener - Tie Down Rope Tightener with Carabiner Clip  to tension the guy ropes. 

I use 1 5/8" fence posts for my antenna masts along with satellite dish j-mounts and guy each one with all of the above going to eye bolts or other tie off points. The biggest antenna is a 6 HF cobweb antenna that is a 8 foot square antenna. The antennas will still sway in high winds but I haven't had any issues even with 50-60 mph winds.

[SteveShannon]

7 minutes ago, WRXB215 said:

I know some people use top rail for antenna masts but it is not engineered for that. You are asking a question that only a PE can answer. @SteveShannon is a PE but he is retired.

Without some kind of reinforcement, the joints on these top rails allow quite a bit of slop.  I use them, but I would not use more than two.  I recommend either guying the top rail sections at the joint and again at or near the top or at least putting in a couple through bolts at the joint or even a sleeve that fits around the joint. I’ve been toying with the idea of a piece of steel cable (wire rope) running the length of the two sections and then tensioned to pull the joint tightly together.  I’m not certain that will remove the play though.  Unfortunately, because of the galvanizing welding is more difficult.

A telescoping flag pole is better in my mind (but not as cheap).

[WRYZ926]

I use several zip screws at each joint. I use 1 5/8' fence post couplers. I went overboard and have three wall brackets along with the guy ring at the top. While fence posts and fence top rails aren't ideal, they do work. Just make sure to properly secure them to your structure and at each joint along with some guy ropes/wires. And keep the weight and wind load down with the antennas. I normally only put 1 antenna on each fence post mast.

[VETCOMMS]

9 hours ago, SteveShannon said:

Without some kind of reinforcement, the joints on these top rails allow quite a bit of slop.  I use them, but I would not use more than two.  I recommend either guying the top rail sections at the joint and again at or near the top or at least putting in a couple through bolts at the joint or even a sleeve that fits around the joint. I’ve been toying with the idea of a piece of steel cable (wire rope) running the length of the two sections and then tensioned to pull the joint tightly together.  I’m not certain that will remove the play though.  Unfortunately, because of the galvanizing welding is more difficult.

A telescoping flag pole is better in my mind (but not as cheap).

Something like this?  Or not sturdy enough

https://servicefirstproducts.com/products/25-freedom-edition-telescoping-pole-black

[WRXB215]

10 hours ago, SteveShannon said:

Without some kind of reinforcement, the joints on these top rails allow quite a bit of slop.

And keep in mind that, over time, that slop and that wind is going to fatigue the joint and it will eventually fail.

As I said in the beginning, some people use top rail and usually they get away with it. But I don't want any of my loved ones around if one ever gives way. It's won't be like a building coming down but it could still cause serious injury or death to an individual.

[WRYZ926]

Fence post can be used safely. You have to be smart about it and make sure each joint is mechanically attached using screws/bolts. And you also need to use proper wall anchors along with guying the mast.

There are plenty of old VHF/UHF TV antennas that were installed using fence posts/top rails 30-40 years ago (if not longer) that are still standing. And VHF/UHF TV antennas are heavier and have a higher wind load than any vertical antenna.

Again, proper installation is important. And not everyone can afford a tower nor is a satellite j-mount always tall enough. Be smart with your installation and your ill be just fine.

PS: You can extend the height of satellite j-mounts using 1 5/8" fence posts and couplers. You will want to use guy ropes/wires when doing so.

Here is my 6 band 6m - 20m cobweb antenna on a j-mount that was extended up with a 8 foot 1 /58" fence post. The coupler is properly attached to the j-mount and fence post along with everything being guyed. The cobweb has a lot more wind load than a vertical and it has withstood 50-60 mph winds just fine.

 

[SteveShannon]

7 minutes ago, WRYZ926 said:

Fence post can be used safely. You have to be smart about it and make sure each joint is mechanically attached using screws/bolts. And you also need to use proper wall anchors along with guying the mast.

There are plenty of old VHF/UHF TV antennas that were installed using fence posts/top rails 30-40 years ago (if not longer) that are still standing. And VHF/UHF TV antennas are heavier and have a higher wind load than any vertical antenna.

Again, proper installation is important. And not everyone can afford a tower nor is a satellite j-mount always tall enough. Be smart with your installation and your ill be just fine.

PS: You can extend the height of satellite j-mounts using 1 5/8" fence posts and couplers. You will want to use guy ropes/wires when doing so.

Here is my 6 band 6m - 20m cobweb antenna on a j-mount that was extended up with a 8 foot 1 /58" fence post. The coupler is properly attached to the j-mount and fence post along with everything being guyed. The cobweb has a lot more wind load than a vertical and it has withstood 50-60 mph winds just fine.

 

Nice!  Great example of guying and bolting the joints.  Do you have a closer picture showing how you bolted the joint?

[SteveShannon]

1 hour ago, VETCOMMS said:

Something like this?  Or not sturdy enough

https://servicefirstproducts.com/products/25-freedom-edition-telescoping-pole-black

I don’t know how sturdy that is, but it’s exactly what I had in mind, but before you buy more, try doing what @WRYZ926 shows with the posts you have. Bolt the joint and guy the masts.  I would guy at the top. The brackets you have will do a good job of supporting the mast below them and all the way to the ground.
I know we always say height is king, but sometimes it’s not necessary.  Does your antenna perform well enough if it’s 15 feet up instead of 20 feet?  A friend of mine use a five foot top rail section partially buried in the ground and a full ten foot section on top of that and then his 2 meter antenna on top of that.  So the antenna tiptop is probably about 22 feet high.  For him that accomplishes everything he needs to do.

[WRYZ926]

8 minutes ago, SteveShannon said:

Nice!  Great example of guying and bolting the joints.  Do you have a closer picture showing how you bolted the joint?

Not handy. I used zip screws at each joint. I put a total of 16 zip screws into each coupler. I have 8 zip screws going through the coupler into the j-mount and 8 more into the 1 5/8" fence post

Here is a photo showing a coupler on one pipe that I have ready to go for my weather station. I will repeat with 8 more zip screws when I add another pipe to the coupler.

[SteveShannon]

Menards also has 21 foot long single joints of fence material. Perhaps all fence material suppliers do:

https://www.menards.com/main/building-materials/fencing/chain-link-fencing/1-5-8-x-21-se-chain-link-fence-top-rail/1715160/p-1464215498543-c-5742.htm

Also, the top rail I have is only 1 3/8” diameter.  The 1 5/8” diameter stuff will be considerably stronger.

[SteveShannon]

12 hours ago, SteveShannon said:

Menards also has 21 foot long single joints of fence material. Perhaps all fence material suppliers do:

https://www.menards.com/main/building-materials/fencing/chain-link-fencing/1-5-8-x-21-se-chain-link-fence-top-rail/1715160/p-1464215498543-c-5742.htm

Also, the top rail I have is only 1 3/8” diameter.  The 1 5/8” diameter stuff will be considerably stronger.

Another 21 foot long top rail, but less expensive if you’re in Washington state:

https://www.everguardmaterials.com/+/galvanized-top-rail-1-5-8-x-21
 

[WRYZ926]

23 minutes ago, SteveShannon said:

Also, the top rail I have is only 1 3/8” diameter.  The 1 5/8” diameter stuff will be considerably stronger.

I went with the 1 5/8" fence post for that reason. Plus it's easier to transport 8 foot sections versus longer sections.

For those interested, here are the 1 5/8" fence post couplers I use.

4 Pieces 1-5/8" X 6" Chain Link Fence Top Rail Sleeve

[WRXB215]

You might take a look at these just for good measure.

roh-9h50.pdf roh-h30.pdf

[Davichko5650]

13 hours ago, SteveShannon said:

 

A telescoping flag pole is better in my mind (but not as cheap).

ChannelMaster Collapsible mast!  Again, not cheap, but stainless steel, designed for antennae mounting. I have my Comet CHA250B up 33' and it has withstood 74 mph winds unguyed.  Absolutrly worth the $165.

[SteveShannon]

12 minutes ago, Davichko5650 said:

ChannelMaster Collapsible mast!  Again, not cheap, but stainless steel, designed for antennae mounting. I have my Comet CHA250B up 33' and it has withstood 74 mph winds unguyed.  Absolutrly worth the $165.

I think the Rohn 9h50 and the channel master are the same thing. 

[Davichko5650]

16 minutes ago, SteveShannon said:

I think the Rohn 9h50 and the channel master are the same thing. 

Most likely. Got mine from Gigaparts or Amazon, forget which. But well made and easy to pull down for inspections and maint on the Comet.  I'm a dyed in the wool vertical guy for HF, enjoy working with limitations and compromises, LOL.

[Davichko5650]

3 hours ago, Socalgmrs said:

 You could have used a satellite dish mount bolted to the house and a better antenna and had much better results for less money and headache. 

That's my plan once I figure out which antenna to throw up for gmrs at the house. Mag mounted to the window a/c is a big compromise.

[VETCOMMS]

11 hours ago, SteveShannon said:

I don’t know how sturdy that is, but it’s exactly what I had in mind, but before you buy more, try doing what @WRYZ926 shows with the posts you have. Bolt the joint and guy the masts.  I would guy at the top. The brackets you have will do a good job of supporting the mast below them and all the way to the ground.
I know we always say height is king, but sometimes it’s not necessary.  Does your antenna perform well enough if it’s 15 feet up instead of 20 feet?  A friend of mine use a five foot top rail section partially buried in the ground and a full ten foot section on top of that and then his 2 meter antenna on top of that.  So the antenna tiptop is probably about 22 feet high.  For him that accomplishes everything he needs to do.

I can always change out the bottom section with a shorter 7 foot section and see if the antenna performs just as well,  i just thought the extra 3 feet would be a good thing.   I like the idea of not guying the mast but it sounds dangerous and unwise not to do so.   What,  specifically do you use for guy wires?  Do you anchor the wires to the edges of the roof near the gutters on the one side of the building and the roof peak on the opposite side of the building?

I like the one guys idea of the telescoping mast that did well without guying.   Will have to look into that. 

[SteveShannon]

4 minutes ago, VETCOMMS said:

What,  specifically do you use for guy wires?  Do you anchor the wires to the edges of the roof near the gutters on the one side of the building and the roof peak on the opposite side of the building?

Dacron rope or wire rope. 
But a high enough bracket can take the place of guys. 
Guys are usually attached to some kind of anchor in the ground, but the edge of a roof should work well also.

[BoxCar]

5 minutes ago, VETCOMMS said:

I can always change out the bottom section with a shorter 7 foot section and see if the antenna performs just as well,  i just thought the extra 3 feet would be a good thing.   I like the idea of not guying the mast but it sounds dangerous and unwise not to do so.   What,  specifically do you use for guy wires?  Do you anchor the wires to the edges of the roof near the gutters on the one side of the building and the roof peak on the opposite side of the building?

I like the one guys idea of the telescoping mast that did well without guying.   Will have to look into that. 

My recommendation is to use a wire rope with thimbles. 

https://www.amazon.com/dp/B0CSYLQCXB?asc_source=01HFY6QA52QM8M7ATBSHXHG6T4&tag=snxs23-20&th=1

[WRXB215]

16 minutes ago, BoxCar said:

My recommendation is to use a wire rope with thimbles. 

Thimbles are a good idea even if you don't use wire.

[Guest]

Fence post is not the right thing to use.  Especially top rail. All that for that little antenna?  You could have used a satellite dish mount bolted to the house and a better antenna and had much better results for less money and headache.