chimney mounted antenna?

[BammBamm]

Chimney is 2 years old and is for gas furnace goes from ground to about 8 foot over roof and is 22" squared. Using 3 chimney mount straps how long of a mast should be used to hold a Mack 5/8 ground plane? If fence pole was mounted from the ground along the side of chimney and attached every 4' up could I go higher? Never mounted to a chimney before but due to trees its the best spot for my friends antenna.

 

[Mudfoot]

10' mast with 4' strapped to chimney. None of that cheap thin walled crap either.

 

[Mudfoot]

On second thought, I don't think I'd go 4' above the chimney. Depends on what straps your using as well. Some straps are flimsy.

 

[RatsoW8]

I can attest that the radio shack chimney strap mount will not hold an antenna like that any more than inches above the chimney if at all. Had a buddy who went up about three feet over the top of the chimney and the straps failed in the first bit of wind..

 

[2RT307]

I would think if you used the pole from the ground up and attached at every 4' as you mentioned, that you would be fine to go 10 feet over. Anything higher than that and I would guy it.


As an alternative, you could use a tripod mount on the roof. They make some really stout ones, or if you're a good fabricator you can make one yourself.


73,
Brett

 

[M0GVZ]

I'm with everyone else. As short as possible above the chimney just so that the antenna clears it. Getting it up higher will provide very little benefit. It won't make any difference to DX and a difference of 10ft or so makes little difference local.

6ft or longer mounting pole bracketed at the bottom and near the top but at least a few courses of brick down from the top of the chimney. Use T K brackets with the T at the bottom. Put a RF choke at the antenna feedpoint and for the PL259 waterproof the connection to the antenna by wrapping it in self amalgamating tape and going over it with PVC. Start wrapping from the coax and work up so that when the coax is installed the turn of amalgamating/PVC tape above the one below covers the lower turn slightly to stop water running in. So many people do it the other way round creating ridges the water can sit on.

 

[Captain Kilowatt]

Personally I don't like chimney mounts. I have seen the mortar and even the bricks crack after years of constant vibrations caused by low winds. Some antennas simply exhibit a vibration in low wind conditions and you never know if you have one or not.

 

[357magnum]

I have to agree with the Capt . , my father-in-law did it with a 5/8 wave Maco years ago even secured with wire's after a few years the chimney needed re-pointing it's cheaper to buy a tripod now than pay a mason later . $$$ IMO

 

[w9cll]

When I lived in Homewood I had a BigStick attached to my chimney for years before I put up my tower, I had no issues but I agree with the others that you're better off with a tripod. We get some good winds in this area.

 

[gamegetter]

my experience has been the same as the captain, i have seen the mortar on those gas exhaust chimneys crumble with age, and the effects of the weather etc....it be your luck it fall apart in the winter when you need it the most and then have your insurance company deny your claim because they find out you had an antenna mast tied to it...

wish i had a suggestion for you but i don't know what other options are available in your home or yard...best of luck hope you come up with something

 

[RatsoW8]

I second the tripod idea or mast from the ground up with the chimney straps for partial support.

 

[KW4HKY]

I have seen very few antenna straps last more than a year. I put a tripod up 5 years ago and it has survived some serious wind.

 

[Shockwave]

This really depends on the quality and condition of the chimney. Being it's only two years old I'm leaning towards a maximum height of 10 feet above the top bracket. In order to do that, you'll need good mast and 4 chimney straps. The top and bottom strap should be doubled up. I used 6 straps on mine since they were from Radio Shack. I figured 6 of them looked as stout as 2 old school Channel Master straps. The straps should be spaced as far apart as possible and no less than 4 or 5 feet. Don't just put it up and forget about it until it comes down either. Check the cement and bricks at least once a year or after a good storm.

While I do not recommend this, I've been getting away with the straps I described holding up an M-104 Yagi and a Gain Master vertical 10 feet above it for almost 4 years. My last inspection absolutely shows signs of failure coming. This Chimney is 60 years old. The outside bricks are becoming loose around the top straps and most of the strength appears to be coming from the fire sleeve inside the chimney now. If I had another option I would use it but in the absence of that, it will stay as is until Mother Nature says no more.

 

[Grogan]

I don't like to climb a ladder or walk on a slanted roof. My grandfather had a flag pole and every day he would raise and lower his flag. I got the idea from him. Mine is scrap iron 6" x 3" angle by 3/8 thick I have about 5' in the ground. you can use angle iron or channel. I bolted it together and cemented it into the ground. the pole is fence post pole and is held by 2 grade 8 bolts 3/8
the bottom stays in place and the top one is removed and the pole is tilted down and rested on a ladder. I can lift an I-max or my new Tornado by myself and the pole is 27' long. I did go longer it was harder to lift and I did bend a top section forcing more than I could lift by bouncing as I struggle to raise. One of these days I want to get 2 sections of sch 80 pipe and make a crank or jig to lift it.

 

[Lil'Yeshua]

My former boss whom had leased a Shell service station back in the eighties mounted a 20' galvanized 2" water pipe that was secured to the building's chimney with custom made steel(think thick)chimney mount brackets that had bolts to tighten each strap along with a Moonraker 4 on top and a Tram D201A and a 90 watt modulator and a D104 mic in his middle office. I and his son used to love talking on it as I could point the antenna in the direction I wanted to talk with awesome results.
That water pipe mast was a bear to erect though.