Putting antennas on house chimneys
 

I've no real experience of putting up antennas on the chimney of a house.

Obviously, I must not overload the chimney breast.

I'm thinking about putting up the following:


______ Discone
/ | \
__ / || \
A |
__ ___|x___ 5 ele.2m yagi
|
B | |
__ |x| 5 ele. marine yagi
| |
C |
| |
__ |x| 5 ele. FM yagi.
| |
D |
|
__ |
/ \ Rotator
/__\
|
| ______
| | | Chimney
| | |
| |

I'm wondering about the spacings, A, B, C, and D.

A, spacing between bottom of the discone and the boom of 2 m yagi.

B, spacing between boom of 2m yagi and boom of marine band yagi.

C, spacing between boom of marine band yagi and boom of FM yagi.

D, spacing between boom of FM yago and top of rotator.

As for the mast, I'm thinking what about 1.5" steel tube.

As for rotator. No idea what model I'd need.

Any thoughts? Am I trying to be too ambitious? I could leave out the
marine yagi if I had to.

Thanks.

Rich.

I'm wondering if your chimney will handle the weight ?
Robert

"Richard" wrote in message
...
I've no real experience of putting up antennas on the chimney of a house.

Obviously, I must not overload the chimney breast.

I'm thinking about putting up the following:


______ Discone
/ | \
__ / || \
A |
__ ___|x___ 5 ele.2m yagi
|
B | |
__ |x| 5 ele. marine yagi
| |
C |
| |
__ |x| 5 ele. FM yagi.
| |
D |
|
__ |
/ \ Rotator
/__\
|
| ______
| | | Chimney
| | |
| |

I'm wondering about the spacings, A, B, C, and D.

A, spacing between bottom of the discone and the boom of 2 m yagi.

B, spacing between boom of 2m yagi and boom of marine band yagi.

C, spacing between boom of marine band yagi and boom of FM yagi.

D, spacing between boom of FM yago and top of rotator.

As for the mast, I'm thinking what about 1.5" steel tube.

As for rotator. No idea what model I'd need.

Any thoughts? Am I trying to be too ambitious? I could leave out the
marine yagi if I had to.

Thanks.

Rich.

On Tue, 17 Feb 2004 17:47:39 -0000, "Richard"
wrote:

I'm wondering about the spacings, A, B, C, and D.

Hi Richard,

You should be thinking more of the tensile failure of the brick mortar
leveraged by the moment of the load above. Chimneys are very strong
to compressive loads, and as brittle as candy to torsion.

The upshot of this is that on a windy night you may find the chimney
in your bed.

73's
Richard Clark, KB7QHC

I've no real experience of putting up antennas on the chimney of a house.

Obviously, I must not overload the chimney breast.

I think your antenna plan is workable.

At one qth I had up a 2 element 10m yagi and a 5 el 2m yagi on a chimney
mount. Replaced those with a 2 el 15/10 quad for a while.

This was with a Radio Shack chimney mount. Just the chimney mount by
itself was too flimsy. I found that it was necessary to add a set of
guys, attached just below the rotator and running to the roof
corners. The guys made the whole thing much more secure and took some
of the windload off of the chimney.

Torsten
N4OGW

I've no real experience of putting up antennas on the chimney of a house.

I have seen chimeys come down in severe wx with just large TV antennas on
them. I guess it would be dependent not only on the structural integrity of
the chimney but also physical size but I certainly would be careful. I
don't know your particulars but wouldn't it be better to have something
bolted on the side of the house even with the insurance issues????

Good Luck and God Bless Tom KI3R

Richard,
I'm not going to tell you that it's workable or not,
I have no honest way of doing so. At least not without
seeing your chimney, or rather putting my hands on it to
see what condition it's in and how well it's put together,
etc, etc. The most realistic thing anyone can tell you is
that in general, chimneys are not built to support anything
except themselves, and do not do well if large 'wind loads'
are placed on them.
The other side of that coin is that people have 'gotten-
away' with mounting antennas on chimneys for years with no
problems at all. Just depends on the chimney and how much
'stuff' you try to tack onto them.
Something else you may not have thought of is what does the
smoke and other combustion products do to the antennas and
rotor on the chimney? Of course, that depends on if you ever
use the 'fireplace', or not. What you burn if you do use it,
and how often you have it cleaned (if ever). You haven't
lived until you've had a chimney fire (LOL), inside or outside
the flue!
'Doc

"Richard Clark" wrote in message
...
On Tue, 17 Feb 2004 17:47:39 -0000, "Richard"
wrote:

I'm wondering about the spacings, A, B, C, and D.

Hi Richard,

You should be thinking more of the tensile failure of the brick mortar
leveraged by the moment of the load above. Chimneys are very strong
to compressive loads, and as brittle as candy to torsion.

The upshot of this is that on a windy night you may find the chimney
in your bed.

73's
Richard Clark, KB7QHC

========================

Better get in a stock of viagra.

Brickwork is weakest when under a tensile stress. So the chimney brickwork
is most likely to fail under tension due to sideways thrust of the wind.

Placing the chimney under torsion causes only a horizontal shear force on
the brickwork to which it is more able to resist.
----
Reg.

Richard wrote:

I've no real experience of putting up antennas on the chimney of a house.

Obviously, I must not overload the chimney breast.

I'm thinking about putting up the following:

______ Discone
/ | \
__ / || \
A |
__ ___|x___ 5 ele.2m yagi
|
B | |
__ |x| 5 ele. marine yagi
| |
C |
| |
__ |x| 5 ele. FM yagi.
| |
D |
|
__ |
/ \ Rotator
/__\
|
| ______
| | | Chimney
| | |
| |

I'm wondering about the spacings, A, B, C, and D.

A, spacing between bottom of the discone and the boom of 2 m yagi.

B, spacing between boom of 2m yagi and boom of marine band yagi.

C, spacing between boom of marine band yagi and boom of FM yagi.

D, spacing between boom of FM yago and top of rotator.

As for the mast, I'm thinking what about 1.5" steel tube.

As for rotator. No idea what model I'd need.

Any thoughts? Am I trying to be too ambitious? I could leave out the
marine yagi if I had to.

Thanks.

Rich.

Check to make sure there are no ordnances against attaching structures
to chimneys. You would do better with a tripod mount on the roof.

Hope this helps...

Irv VE6BP
--
--------------------------------------
Diagnosed Type II Diabetes March 5 2001
Beating it with diet and exercise!
297/215/210 (to be revised lower)
58"/43"(!)/44" (already lower too!)
--------------------------------------
Visit my HomePage at http://members.shaw.ca/finkirv/
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--------------------
Irv Finkleman,
Grampa/Ex-Navy/Old Fart/Ham Radio VE6BP
Calgary, Alberta, Canada

Reg Edwards wrote:

"Richard Clark" wrote in message
...
On Tue, 17 Feb 2004 17:47:39 -0000, "Richard"
wrote:

I'm wondering about the spacings, A, B, C, and D.

Hi Richard,

You should be thinking more of the tensile failure of the brick mortar
leveraged by the moment of the load above. Chimneys are very strong
to compressive loads, and as brittle as candy to torsion.

The upshot of this is that on a windy night you may find the chimney
in your bed.

73's
Richard Clark, KB7QHC

========================

Better get in a stock of viagra.

Brickwork is weakest when under a tensile stress. So the chimney brickwork
is most likely to fail under tension due to sideways thrust of the wind.

Placing the chimney under torsion causes only a horizontal shear force on
the brickwork to which it is more able to resist.
----
Reg.

All this presupposes the chimney is brick.

Mine is cast concrete and has had a big TV antenna on it for years and
this is a high wind area.

There is a smoke and soot problem and I only run the fireplace a few times
a year. I wouldn't put an expensive ham antenna (or a rotor) up there.


--
Jim Pennino

Remove -spam-sux to reply.

On Tue, 17 Feb 2004 20:01:40 +0000 (UTC), "Reg Edwards"
wrote:

sideways thrust of the wind.
=
Placing the chimney under torsion