On Sun, 04 Oct 1998 04:31:39 GMT "Rick Bullon" <kc5ajx@hotmail.com>
writes:
>
> First I would like to again thank all who helped me on my trig
>question post. After I took the info and plotted out my proposed 70ft
>Rohn 25 tower, it took up less area than I thought so now I'm going to
>change plans and go up to 100ft!!
>I tried to use the formula I received from the list but I guess I am
>stupid when it comes to trig. I couldn't get the new dimensions right
>so
>I figured if the old guy points of 56ft ( rohn 25 at 70ft 70 mph) and
>the new guy points are 80 ft ( Rohn 25 100ft 70mph) the difference is
>24
>ft, so if I add 24 ft to the distance from the property line ( which
>the
>old figure was 28ft)this would move the tower to 52ft Right? or am I
>totally wrong again?
The distance from the property line is 1/2 of the guying baseline, or
40 feet in this case.
For every foot of guy elevation, you can move the guy
point in by 0.8 foot to keep the same 80% guying angle. You can
then place your tower closer to the property line (1/2 of the
new guying baseline).
For example, if the guys are elevated 8 feet, the baseline is
shortened by 6.4 feet, to 73.6', and the tower base can move to
36.8' from the property line.
> If I use Phillystran for the top guys then I can use the 3/16" EHS
>for
>the other guys right?
Yes.
and I think I read on here somewhere than the
>cost
>is about of using Phillystran is about the same as using the EHS &
>insulators to brake up the guys Right?
Maybe Philly is a little more expensive, but I think it's worth it.
> I noticed something strange while studying the Rohn book the other
>night. I was looking at the difference between Rohn 25 @ 70ft and 100
>ft, I mistakenly open to the Rohn 45 section instead of the Rohn 25
>section I noted the the allowable area for round and flat member is
>higher for Rohn 25 than for Rohn 45 at the same height is this a
>misprint? My book is dated Dec 1997
The general notes on the Rohn 45 guying layout dwg states that the
designs include three side-arms with a projected area of 8 square
feet, so you can add 8 sq feet to the rated capacity of Rohn 45.
> Another thing with the current thread on rebar cages I noticed that
>the
>Rohn book doesn't call for one. I can only assume that the rebar cages
>are for crankups or another brand of tower or is this another issue I
>have to consider? I wasn't planning to use one in my plans.
Rebar is required. Look at Rohn dwgs C610621 and C620643.
> Well again this post is longer than I had planned I will probably
>have
>more questions later HI HI
Just a general comment on your plans. 100' is WAY too high for
your lowest 10 and 15 meter antennas. You might want to consider
switching to Rohn 45, which requires guys only at the 50 and 100'
levels. You would save some money on the guying materials, have a
higher capacity tower, and have more room to swing another antenna
at the 51' level on a ringrotor or sidearm.
Dave Hachadorian, K6LL
Yuma, AZ
K6LL@juno.com
> I know it has been stated before but this is the BEST place for info
>on
>towers and antennas anywhere Thanks again guys!!!
>73
>Rick
>KC5AJX
>
>
>
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