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Author Topic: antennas  (Read 1136 times)
K0BLR
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Posts: 57




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« on: April 24, 2009, 07:13:17 AM »

Hi everyone,

 I am looking at a 2 bedroom house in Maple Lake, MN. There are plenty of trees for hanging a G5RV. However the problem is how do I put my collinear dual band vertical? There is a pretty good pitch on the roof. Any thoughts?

73,

Ben K0BLR
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N5VTU
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Posts: 363




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« Reply #1 on: April 24, 2009, 12:03:45 PM »

What about a push up mast mounted to the eave of the house? Another choice, may be to use a light duty tv type mast with a tripod mount or a chimney mount (assuming you have a chimney). Whatever you decide, be careful not to exceed wind load ratings, especially if you go with a chimney mount.

Good Luck  
       
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WB2WIK
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Posts: 20603




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« Reply #2 on: April 24, 2009, 08:23:15 PM »

Tower, ground mounted, in concrete, and guyed per manufacturer's ratings.
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W3LK
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Posts: 5639




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« Reply #3 on: April 25, 2009, 06:54:56 AM »

<<  a chimney mount (assuming you have a chimney). Whatever you decide, be careful not to exceed wind load ratings, especially if you go with a chimney mount. >>

There is no such thing as a wind load rating for chimneys.

This is a BAD idea. Chimneys are designed to carry smoke and exhaust products away from a furnace or fire place. They are designed to support only their own weight. They are NOT designed to support antennas or withstand the lateral and torsional forces imposed by masts and antennas. Add to that the corrosive effects of flue gasses on aluminum and you will not only weaken your chimney, but destroy your antenna within a couple of years, maybe less, depending upon how active your chimney is.

Yea, I know, there have been TV antennas fastened to chimneys for years, and virtually every one of them has cracked mortar joints and are in a weakened condition. BTW, damage caused by a failed chimney that's been supporting antennas likely will not be covered by your property insurance or your liability insurance in the event the chimney falls on someone. It may, but I wouldn't bet on it.

There are so many better ways to support antennas.

73,

Lon - W3LK
Naugatuck, Connecticut
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N5VTU
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Posts: 363




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« Reply #4 on: April 25, 2009, 10:29:04 AM »

Ben,
Lon's point about chimneys is valid, hence my warning.  My chimney is not brick and mortar, it is a wood framed structure sheathed with hardi-plank covering the actual "ckimney" if you will, which is a piece of 8" round galvanized ductwork inside the pretty hardi plank covering.  I tend to forget about brick and mortar chimneys as those are pretty rare around my QTH, and just assume that most chimneys are like mine.  By all means if you have a brick chimney, heed Lon's advice.  If on the other hand, you have a framed chimney like what I've described, that is securely tied into the roof framing members, you can probably get away with something light duty.

Good Luck.
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W3LK
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« Reply #5 on: April 25, 2009, 11:56:59 AM »

Robert:

I would still be hesitant to mount much of anything on a framed chimney. You simply don't know, unless you watched it being built, just how securely it is fastened to the frame of the house. Most that I have seen have just been toenailed to the frame because the architect/builder never envisioned it being anything but a cover for the flue.

Even the typical dual-band vertical needs a much more secure mount than any chimney can provide. My Comet GP-9 is fastened to the corner of the second floor by a 6 inch Channel-Master corner mount that is spaced 5 feet between the two pieces and uses 4-inch lag bolts into the 4x4 that frames the corner. The base of the antenna is just two feet above the roof line.

The only problem I have had was this past winter when it got coated with about 1/2 inch of ice that broke away from the antenna in a wind storm in the middle of the night. It scared the bejesus out of my wife and me when all the ice hit the roof. <gg>

It didn't do a thing to the antenna or the mount, however. Some things I just like to over-engineer.

73,

Lon - W3LK
Naugatuck, Connecticut
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K0BLR
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Posts: 57




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« Reply #6 on: April 25, 2009, 12:46:31 PM »

Hi Lon and Robert, and wwhomever is reading this,

 If you two like to see pictures of what I might be up against I will be gald to go back to maple Lake and Take pictures. I can't say for certain what the composition is of the chimmeny.
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W3LK
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Posts: 5639




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« Reply #7 on: April 25, 2009, 01:08:41 PM »

Ben:

Neither of us is trying to be unkind or minimize your dilemma. You asked advice on where to mount your dual-band antenna. You received a response that Robert and I think is a bad idea.

The same poster also suggested a push-up mast along side of the house or a tripod mount on the roof. Either one is MUCH preferable to using a chimney.

The important thing is to mount the antenna in a safe and secure manner that will not fail. A chimney mount does not fit that description; both the push-up mast and a properly installed tripod mount do.

Ultimately, the decision is your responsibility and you must deal with any ramifications of it.

73,

Lon - W3LK
Naugatuck, Connecticut
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W3LK
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Posts: 5639




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« Reply #8 on: April 25, 2009, 01:11:00 PM »

One other possibility -

You could mount it in the top of one of the trees. I've seen this done a few times, but the antenna MUST clear the top of the tree.

73,

Lon - W3LK
Naugatuck, Connecticut
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W3LK
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Posts: 5639




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« Reply #9 on: April 27, 2009, 07:32:39 AM »

Ben:

See my reply to your email.

73,

Lon - W3LK
Naugatuck, Connecticut
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AC7GI
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Posts: 7




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« Reply #10 on: November 19, 2009, 09:00:55 AM »

I going to lose my house in a few weeks or months.  I just purchased a Hy-Gain Explorer-14 antenna and Ham-IV rotor.  My problem is not having a tower.  I will be renting for a few years and then back in the business of owning a home in a few years and then a tower mount.  Is there any way around a temporary set up for an antenna that size on a pole mast. Can that be done safely. Looking for Ideas.  This will be the best antenna I've ever owned.  I only used G5RV's before
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