On 12/13/2011 3:35 PM, jcjacobsen@q.com wrote:
> Gary wants to know:
>
> <snip>
> I may put up a Rhon 45G but prefer free standing with bracket to house at
> 8-10 feet and mounted in adequate cement. What level would be safe - 3
> sections be ok?
>
> Is there a formula?
> <snip>
>
> Gary.........
>
> Google Rohn Towers, click 45G, and then Bracketed Towers. All the info should
> be there. Make your own conclusions.
>
> Oh, some info NOT contained is: with a tower brackted to the house, every,
> and I do mean EVERY, little noise from antennas is heard in the house. Got a
> yagi, and it slaps in the wind against the rotor stops? You hear the bang.
> Elements vibrate in the wind? You hear them. In short, if you bracket to the
> house, if you can, put it off the garage end and not by the bedrooms. Oh, and
> please, don't ask me how I know
I don't have my ROHN catalog in here, but:..
Over the years, I have had quite a few towers at different locations.
When at Breckenridge MI, I had a 5L 20m KLM on a tower bracketed to the
end of the roof. (It also was guyed) Like here, those roof members were
constructed of heavy lumber for strength. I have 40' up of a 50' 25 G
on the West end of my shop currently with a 24' gin pole and a number of
ropes. You can hear that one outside on a windy day.
The one in Breckenridge was on the other side of the wall from the head
of the bed.
I have never heard any sounds through the walls from these
installations. For one I use vibration damping clamps which are
relatively simple to make and similar to the two bolt conduit clamps. I
typically cut a piece of innertube the same height (or even higher) as
the clamp and wrap one or two layers about the tower leg(s) where
it/they are clamped. The clamps are slightly over size to allow for the
rubber and are installed very tight, compressing the rubber isolator.
Because of the large clamping area the mounts behave as would a regular
metal to metal clamp, but the rubber serves as a sound isolator or block.
I've been using this clamping method for nearly 50 years and be it
tribander, monobander, wire antennas, or trap verticals, I've never
noticed a noise problem.
The bracket on the shop is very rigid being constructed of 12 ga, welded
3/4" square steel tubing and 1/8" thick steel plate.
I also orient the tower so it has two legs parallel to the wall or roof
with the two that serve as a hinged base at a 60 degree angle to the
wall or roof although the original intent for that was to miss a tree
when I let the tower down. <:-))
HOWEVER be warned that when bracketing a tower to the end of a house
that wall may have to provide a lot of support for the tower if you
experience strong winds. You'll note that bracketed towers are not a
whole lot taller than the same tower used free standing and the wind
load is quite small. For those that put much on the tower, or succumb
to the temptation to add another section or two that wall may end up
serving the purpose of replacing guy wires and most walls are not
designed to hold that sort of load. If the tower goes down, it is
likely to take most of the wall with it.
When bracketing much of anything, install plates (usually on both sides
of the wall) to distribute the load across multiple studs and stick
strictly to both the height and load recommendations from the tower
manufacturer..
Stick within the bracketed ratings (usually available on the
manufacturer's web sites) and it should be fine. Use the sound
isolation and you may be surprised at how much they will quiet the tower.
73 and good luck,
Roger (K8RI)
> this.
>
> K9WN Jake
> ___________________________
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