[time-nuts] Freestanding mast
wb6bnq at cox.net
Sat Sep 4 01:38:17 UTC 2010
Actually the Rohn HDBX towers went up to 64 feet (not counting any pipe used to
mount the Beams) free standing as I have one. What happens is the amount of
allowed loading decreases with height. Just sticking up a GPS antenna would not
overload a HDBX at 64 feet.
You are right about it being a PITA as for climbing. Each section is only 8 feet
in length but narrows as it goes up. It is possible with the right base to have
it in a tilt-over arrangement. Otherwise, it helps to rent a man-lift to do the
assembly if you got the guts to go in one.
Tom Holmes wrote:
> Rohn's HDBX series would go to 50 feet, free-standing. It is a real pain to
> climb because the braces cross in an 'X' pattern, but is quite sturdy. Two
> reasonably fit climbers plus a one person ground crew could put it up in a
> few hours once the base is ready. These towers tend to twist more than rock,
> unlike Rohn 25, 45, or 55.
> For your minimal load GPS antenna, even the BX series would be adequate, but
> I don't believe there is a 50 foot version.
> Now that I think about it, Rohn sold off all of the various BX series, and
> it is now marketed by Thomas & Shelby.
> Any piece of tubing you would try to take to 50 feet would likely buckle
> under its own weight and length pretty quickly (all of you ME's and physics
> majors can correct my terminology and choice of failure modes off list, the
> point being that it WILL fall down if you can even get it put up), and would
> definitely need to be guyed.
> This leads me to another possibility, if money is not a concern. One ham
> friend of mine has a 120 foot tower that is based on those tapered lighting
> supports you see along the freeways. It is galvanized and consists of three
> sections that simply nest for about a 10 foot overlap. Of course, it takes a
> crane to assemble. Remember, I said if money is not a concern...but it does
> look very nice and serious and professional. Climbing it is not for the
> faint of heart, believe me!
> Tom Holmes, N8ZM
> Tipp City, OH
> > -----Original Message-----
> > From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> > Behalf Of Charles P. Steinmetz
> > Sent: Friday, September 03, 2010 1:08 AM
> > To: Discussion of precise time and frequency measurement
> > Subject: Re: [time-nuts] Freestanding mast
> > Stanley wrote:
> > >ROHN 9H50 34 Foot Telescopic TV Wireless Antenna Push Up Mast
> > Interesting suggestion. Rohn is well known to me, though I don't
> > typically think of them for things like push-up masts.
> > For those suggesting 6-10' of pipe, at my rooftop I get a reception
> > cone of about 50 degrees elevation and above during the vegetated
> > months (say, mid-March through mid-November), and about 30 degrees
> > and above in the dead of winter, due mostly to dense tree cover that
> > is 60-80 feet tall. So, I'd really need to get 20 feet + above the
> > chimney (50+ feet above the ground) for a significant
> > improvement. The suburban residential lot size doesn't leave me much
> > to work with (no centrally-located tower, therefore no guys unless I
> > negotiated easements with the neighbors, and Hell will never be that
> > cold...). I doubt I could get a permit for 80' of Rohn 55. Maybe if
> > I put a wind generator on it....
> > Thanks again,
> > Charles
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