I will probably get flamed for this, but I can't resist. Aren't those Rohn
specs for 45G super conservative (8sq ft at 90 MPH) because they
place the top set of guys so far below the top of the tower? I would expect
that a properly guyed 70' x 45G tower would be capable of holding up
20 sqft+ in a 90 MPH wind if the top set of guys were placed reasonably
close to the top of the tower. For that reason alone I would go with the
45G tower. On the other hand, getting antennas on and off the guyed tower
is a little more work (tram line) versus straight up and down. Also if you
are interested in vertically stacking antennas along the length of the tower
you have the problem of guy wire interaction to worry about. This can be
solved by going to Kevlar or Fiberglass guys, but I think it adds to the
cost (versus steel guys):
Rohn 45
PROS
Smaller base
Larger antenna windload capacity - 20sqft (with properly engineered guy
system)
Fall zone probably smaller (heaven forbid)
CONS
Steel guy wires need to be broken up or replaced with insulated material
Tram line needed to remove/install antennas
Guys vulnerable to falling trees and vandalism (kevlar vulnerable to fire)
Probably less appealing to neighbors
SSV Tower
PROS
Antennas easily hoisted up and down
No Guy wires and guy wire electrical interaction
More appealing asthetically (to non-hams)
CONS
Lower windload capacity
Larger concrete base
Probably has (or a least potentially has) a larger fall zone
That is the trade space as I see it, Chuck. I would probably
opt for the 45G if it were me.
Good luck!
73 de Mike, W4EF.............................................
----- Original Message -----
From: "Chuck Counselman" <ccc@space.mit.edu>
To: <towertalk@contesting.com>
Sent: Monday, September 30, 2002 7:15 AM
Subject: Re: [Towertalk] 45G (guyed) vs. SSV (self-supp'g) 70-ft. tower
> At 8:59 AM -0400 9/30/02, K7LXC@aol.com wrote:
> >In a message dated 9/29/02 8:48:19 PM Pacific Daylight Time,
> >ccc@space.mit.edu writes:
> >
> >> Can anyone give me an estimate of the overall cost of each
> >> alternative (45G or SSV), considering not only the tower itself but
> >> also the foundation work, professional erection, and guying (for the
> >> 45G)?
> >>
> > > In other words, what's the net cost of doing without guys?
> >>
> >...You can gather the steel costs yourself - check Texas Towers or other
> >Rohn dealers.
>
> I'd already done that. The difference in steel cost is not
> significant. The _erection_ of a 70-ft. SSV tower is what worries me.
>
>
> >...if you want the least expensive 100' antenna structure and
> >have the real estate and spousal approval, you can't beat a guyed system.
>
> I know that a guyed system is cheaper, but by how much? $3k, $30k,
> or what? Just approximately.
>
> I'm short on real estate. Guy anchors would have to go in the
> "setback(s)" of my lot. Obtaining zoning approval may be difficult
> and could force me into compromises that I want to avoid.
>
> -Chuck, W1HIS
>
>
> _______________________________________________
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>
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