[TowerTalk] How many tower sections i can install??

[Gary J - N5BAA]

Try one of the NA4RR Hexbeams  http://www.k4hex.com/home.asp.  The Hexbeam 
doesn't want to be much above 30-35 feet for optimal performance and is very 
light weight.   At our Field Day we had one at 20 feet that clearly out 
performed a tribander at 36 feet.  We found the Hexbeam to be very 
directional.  Could hear off of the sides and back, but it really wants to 
talk off the front.  Found Guam with a good pileup going and got him twice 
on 20 meters (GOTA and regular) each on the first call.  Same for the 4 
Hawaii stations we found.  My bet is there is some parasitic influence from 
all of the extra reflectors and the extra driven elements acting as 
directors (the Hexbeam had wires for 6/10/12/15/17/20 on it)

Gary J
N5BAA

-----Original Message----- 
From: Alex Malyava
Sent: Wednesday, August 26, 2015 10:50 AM
To: TexasRF at aol.com
Cc: Douglas M. Ruz Sobrado ; towertalk
Subject: Re: [TowerTalk] How many tower sections i can install??

since we are talking about 30' short "tower" on the building roof, why not
to use some sort of pipe instead of pretty heavy Rohn sections?
I don't think it is a big deal to find or weld 9-10-12m long tubular mast
that will be able to support a spiderbeam or some other lightweight
tribander.

On Wed, Aug 26, 2015 at 11:22 AM, TexasRF--- via TowerTalk <
towertalk at contesting.com> wrote:

> Hi Douglas, you can achieve a a greater guy point distance by using four
> guys instead of three. You would not want the guy to guy angle to exceed
> 120
> degrees in any case.
>
> Your roof dimensions would allow guy to guy angles of 120, 60, 120 and 60
> degrees. With the tower mounted in the center of the roof and assuming the
> anchors are at the edge of the roof, a guy to guy angle of 120 degrees,
> the
> distance would be 20.0 ft to the anchor. The distance between anchors
> would be 34.6 ft, 20 ft, 34.6 ft and 20 ft.
>
> So, in this case, you could guy the tower a couple of ft below the top and
> three 10ft sections would have a anchor/height ratio of 66.66%.
>
> We typically use an 80% ratio mainly because that is the number Rohn
> specifies for all of their tower models. It is a good compromise between
> load
> capacity and space required.
>
> Considering that these towers are used up to 180ft in height or more, it 
> is
>  reasonable to move anchor points inward for reduced heights. The issue in
> doing  this is that Rohn has no published data for doing this. The wind
> load
> rating has  to be reduced and it takes engineering skills to properly do
> the calculations.  It is not rocket science however.
>
> I would be concerned about possible roof damage as much as the tower
> surviv
> al. It is conceivable that using the roof edge as a turning point for the
> guy and then a ground anchor would be stronger. Something else that would
> benefit from an engineers blessing.
>
> 73,
> Gerald K5GW
>
>
>
>
>
> In a message dated 8/25/2015 9:14:22 P.M. Central Daylight Time,
> co8dm at frcuba.co.cu writes:
>
> Hi,
>
> I would like read your ideas.
>
> I have few 10 ft  section of a tower (it is like a Rohn 25G).
>
> I would like install few  section over some part of my roof...The roof is
> concrete...as you know many  house in the Caribbean has concrete roof 
> ...it
> is 24ft by 40ft...so, i have  calculating and the distance from the base 
> to
> the guy anchors is 14 ft  !!!
>
> I know the distance from the base to anchor points is 70 % of the  tower
> height...so, 70% of 20 ft is 14ft, that´s mean 2 tower sections...right
> ??...Is it possible install 3 sections adding more guy´s set  ???
>
> Thanks,
>
> 73....Douglas,  CO8DM
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