yagi five element beam antenna

[radioshane]

I'm just wondering if putting a five element marine band yagi with a rotator on it and on a 8 foot pole is safe on a chimney ?
Has I have seen various videos on youtube of yagis on chimney s !

 

[trap5858]

It should not be a problem as long as the equipment is properly secured to the chimney. This antenna would be no heavier than a conventional TV antenna. Observe proper safety precautions when mounting it please.

 

[lep]

When Direct-TV was servicing my system recently they removed my SAT dish which had been professionally mounted to a chimney. They told me that for safety reasons they are no longer permitted to use chimney mounts even though they still had the hardware in stock. Just for info.

 

[radioshane]

Trap 5858 it's 5 and half foot yagi

 

[jim202]

I'm just wondering if putting a five element marine band yagi with a rotator on it and on a 8 foot pole is safe on a chimney ?
Has I have seen various videos on youtube of yagis on chimney s !

Having seen for many years, people having their TV antennas and rotators mounted on their chimney's, all I can say is way back when workmanship meant something, even those chimney's developed cracks and started to come apart. Remember, a chimney is designed to only hold the downward weight of the bricks and mortar. They are not designed to withstand side way momentum or heavy vibrations.

Placing an antenna and rotators on a chimney exerts forces that the mortar and brick were never designed to stand up against. The higher above the chimney you place this force, the faster the chimney will come apart.

Bear in mind that it may seem like a fine place to place your antenna on. It's a high spot and the mounting straps are available all over the place at a cheap cost. But at what cost are you saving when you have to hire a company to come in and have them re-build a chimney that was probably in good shape before you made a bad choice? How much is it going to cost to repair your roof when the bricks fall off and put a hole in your roof? Ever see a chimney crack about 3 feet down and topple over?

You would be much better off using a house bracket that bolts to the side of your house. Just make sure that you tie in the lag bolts to the studs and not rely on the siding to hold up the antenna bracket. If not, your now looking at repairing the side of your house.

An even better solution is to put up a tower or use a roof bracket stand to hold your antenna. just remember to seal up the holes where the lag bolts go into the roof. make sure you tie the bolts into the roof rafters so you don't rip the roof up from high winds in a storm.

Keep the mast as short as possible. The higher or further the load (antenna and rotator) is above the mounting point, the more the forces are on the mounting bracket or brackets. You can't change physics.

 

[radioshane]

jim on a website from a called QRZ.com and callsign W3CP he has is 7 element on his chimney on a little pole and it be a longer yagi than mine because more elements mean longer antenna

 

[radioshane]

I already have my yagi on the rear of my house with two t and k brackets with a 30 foot pole but with a rotator on it it would be to top heavy
and the pole on the chimney would only be 8 foot

 

[SCPD]

Chimney mounts

I agree with all those who say avoid a chimney mount if you can. You're better off going to the Lowes or Home Depot, buy a 20' piece of fence top rail, and mounting it on the back of the house or a fence post next to the house. If you're nervous that your 5 element beam and rotor will fold the top rail, there's your sign that the chimney mount would of been too much of a strain.

But if you truly have your heart set on a chimney mount, the thing you want to avoid is the straps digging into the brick and mortar. Running some cheap angle iron under the straps (a cut up bed frame can be had from thrift stores) the length of the chimney, and spacing out the two straps as far as possible will alleviate a lot of the strain. If you think it's gonna be up there for more that a couple years, give the angle iron a couple coats of paint first so you don't have rust trails running down your shingles.

 

[DJ11DLN]

Having seen for many years, people having their TV antennas and rotators mounted on their chimney's, all I can say is way back when workmanship meant something, even those chimney's developed cracks and started to come apart. Remember, a chimney is designed to only hold the downward weight of the bricks and mortar. They are not designed to withstand side way momentum or heavy vibrations.

Placing an antenna and rotators on a chimney exerts forces that the mortar and brick were never designed to stand up against. The higher above the chimney you place this force, the faster the chimney will come apart.

Bear in mind that it may seem like a fine place to place your antenna on. It's a high spot and the mounting straps are available all over the place at a cheap cost. But at what cost are you saving when you have to hire a company to come in and have them re-build a chimney that was probably in good shape before you made a bad choice? How much is it going to cost to repair your roof when the bricks fall off and put a hole in your roof? Ever see a chimney crack about 3 feet down and topple over?

You would be much better off using a house bracket that bolts to the side of your house. Just make sure that you tie in the lag bolts to the studs and not rely on the siding to hold up the antenna bracket. If not, your now looking at repairing the side of your house.

An even better solution is to put up a tower or use a roof bracket stand to hold your antenna. just remember to seal up the holes where the lag bolts go into the roof. make sure you tie the bolts into the roof rafters so you don't rip the roof up from high winds in a storm.

Keep the mast as short as possible. The higher or further the load (antenna and rotator) is above the mounting point, the more the forces are on the mounting bracket or brackets. You can't change physics.

+1. I have seen many chimneys over the years that were damaged by antenna mounts, usually TV or CB antennas. It's not a pretty sight, especially when one collapses. Let the chimney be what it was built to be, a chimney. An eave mount or a tripod will serve your needs and if properly installed is a lot less likely to damage your home.

 

[radioshane]

Wyandotte I don't mean top heavy on chimney I mean I have 30 foot pole allready starting from just above my back kitchen to a couple a feet above the chimney which with the windy conditions has been moving around and if I put rotator on it would be dangerous !
I would put a photo on hear but I don't know how to do it

 

[902]

When I first got into ham radio, I had one mast on a vent pipe and another mast anchored to the chimney with straps. This was up in NJ, which was relatively safe, but on occasion we'd get a nor'easter or hurricane come through. So, I had a TV rotor (very light duty) with an 11 element 2 meter beam on top (that's very close to the marine frequencies). Never any problems with that. Then I added a 10 meter monobander (it was pretty light). No problems with that. Then I changed the rotor to a Ham 3, with schedule 40 pipe. I put a Moseley tri-bander up (along with a 2 meter antenna and a 440 yagi). It was fine for a while. Then it blew over in a windstorm and took the chimney with it.

So, I lived that "chimneys are made to be chimneys" thing. The other consequence was that the fall damaged the roof and also sent some bricks down to the driveway. Not a good thing, as until I could afford to fix the roof, I had water coming in every time it rained. It was just a disaster.

If your chimney is painted over and maybe even tarred, you have no idea if the mortar is spalled, if the bricks are cracked, etc. All of that affects mechanical integrity. If the chimney is in good condition and you put a light weight antenna on it (note that most TV antennas are extremely flimsy), you'd probably be fine. The more you hang off that bracket, the more force it will transfer to the chimney. The guys are right. Chimneys aren't made to deal with that. With enough crap up there, you'd eventually end up like I did when I was a kid.

 

[DJ11DLN]

Wyandotte I don't mean top heavy on chimney I mean I have 30 foot pole allready starting from just above my back kitchen to a couple a feet above the chimney which with the windy conditions has been moving around and if I put rotator on it would be dangerous !
I would put a photo on hear but I don't know how to do it

So to be clear, this pole is mounted to the side of your house? Or am I misunderstanding? Is it attached in more than one place, i.e. also at the eave? If so, and it's moving around like that in the wind, I would not chance putting a rotor up there. If it's not, you might want to attach it at the eave/roof line, whereupon it may hold up to the weight and mass of the rotor. The Yagi you're contemplating isn't too big of a deal wind load-wise...but hanging that hunk of rotor up there on something that already moves around in the wind...I would not chance it. If it's only secured down low, you get into some pretty nasty moment arms between there and the top. Photos would help; click the reply button to get the advanced tools. Look for the little paperclip at the top of the text window, right next to the smiley button. Click it and follow the prompts to upload your pictures.

Don't get me wrong, I'm not trying to discourage you...but there's a right way and a wrong way to accomplish what you're trying to do, and the wrong way could result in damage to your house, which we all want to avoid if possible. And if the mast -- and what's mounted on it -- wasn't installed properly in the first place, you may get into claim issues on your homeowner's insurance if it does fall and damage the roof, a window, siding/fascia, or whatever. That's a headache nobody needs.:wink:

 

[DickH]

Wyandotte I don't mean top heavy on chimney I mean I have 30 foot pole allready starting from just above my back kitchen to a couple a feet above the chimney which with the windy conditions has been moving around and if I put rotator on it would be dangerous !
I would put a photo on hear but I don't know how to do it

Why don't you just accept the good advise you have gotten and DON'T use the chimney.
All you want to do is argue for your idea.

 

[radioshane]

I don't want to argue I was just busy that's was all

 

[radioshane]

my photo can be found on imgur my name on there is dadioshane

 

[radioshane]

906 how tall was your pole when it was on your chimney stack and the seven element yagi must of been bigger than mine !

 

[902]

906 how tall was your pole when it was on your chimney stack and the seven element yagi must of been bigger than mine !

It was in the very late 70s/early 80s. I'm thinking I had 5 ft. of 2" galvanized Schedule 40 (yes, BIG pipe) strapped to the chimney, the Ham3 rotor and 10 ft. of lighter weight exterior EMT on top of that. The EMT bends, and did in one windstorm. There was a Cushcraft 11 element yagi at the top, a UHF yagi that was end-mounted (it had a log periodic driven section with a pipe balun... don't exactly remember the manufacturer, but it's not made anymore), and a Moseley TA-33Jr. with 40 meter traps. It was a delicate balancing act.

Thing is, with my lack of experience at that age, I thought I could balance a battleship on that chimney. Wasn't the case. If I left it lighter-duty with the 11 element yagi and maybe the 432-460 yagi up there, I might have been fine.

There's a concept called "flat plate wind load." It's the surface area of everything you have up in the air all added up to form a square flat plate, and is measured in square feet. Now, imagine a windy day, and you're standing on the roof trying to hold a 40 pound metal square that's 3 ft. by 3 ft in one hand (I think mine was heavier and larger than that). Think about the force the wind applies to it as it hits the metal broadside and makes it act like a sail. How does your hand feel? Would you be able to hold it? Those are the kinds of forces you have to prepare for.

I tried a bunch o' stuff like that "coming up" in radio. Another time, I nailed and tied a bunch of 5 foot wood 1x2s together to support a Radio Shack high band quarter wave ground plane. That came down in the neighbor's pool. They've passed, but I'm still friends with their kids on social media and every once in a while they razz me about that.

 

[NDRADIONUT]

The crap coming out of the chimney also coats your antenna....

 

[902]

The crap coming out of the chimney also coats your antenna....

It sure does. I owned a 440 repeater that used an exposed dipole array that was installed on an apartment building roof right next to the chimney. It was also up near the intersections of several busy Interstates. My coverage got worse and worse. The grime was all over the phasing harness and elements. I had to take the thing down and use steel wool and phosphoric acid ("naval jelly") to clean the grime off. I didn't notice this on the antenna I had up at home, though.

 

[KC4RAF]

Imagine if you would, a chimney mount

system squeezing the bricks together to hold your antenna; now over a period of time that squeezing tends to loosen the mortar holding the bricks in place. There is nothing in the chimney to stop the moving/squeezing action of the mount. You will have wind, rain and the heating/cooling of the day/night, all of which will cause the mortar to weaken. After a length of time, ( months, maybe years) there will be a disaster. Using a mast or tower is the only way to safely mount an antenna.