Hi Craig,
Your story is similar to mine. I see you are in Reno. I am in Las
Vegas. Clark County, the City of Las Vegas, and the City of Henderson
(where I live) all have gone to IBC-2000 90 MPH wind calcs here. Used
to be UBC-97 at 70 MPH. The tower I was planning to purchase from US
Towers can't meet the 90 MPH wind specs. I have to go with their HD
Tower to meet the requirements. I am caught in the middle between the
PE at US Towers and my bldg dept. The latest episode is I thought I
had everything I needed from US Towers then the city bldg dept guy
tells me there are different categories in IBC-2000 for wind calcs.
He tells me category A, B, or C, (whatever they are) won't pass, it
must be category D or better. Now the US Towers PE says towers don't
come under this category section of categories and to tell the bldg
dept guy to look in IBC-2000 section 3801 which address towers
specifically. So it's back to City Hall tomorrow morning. If it
ain't one thing it's another. Also, be advised all the eng stamps
(wet stamps) have to be from a Nevada PE. The US Towers PE, in
California, also holds a Nevada PE stamp, so I am lucky in that
respect.
We also have the variance cut off at 45 ft. I decided not to get the
variance as letters and forms will be sent to all the neighbors in a 2
block area. If one neighbor objects there will be a hearing. Too
risky and too time consuming for me. I will go with a 40/45 ft tower
and after it is up and all the dust settles try to get it another 10
ft or so with a HD mast. No big antennas plans, just a standard 3 el
tribander.
Good luck in your efforts. Hope it goes easier for you than it has
for me.
Craig Sande wrote:
>
> At this time I am only in the early stages of planning a tower installation
> at a new QTH. The local planning board has changed their tower ordinance, so
> I will need to request a variance (called administrative permit $883) for
> anything above 45 feet. The building department requires an engineers stamp
> to certify that the structure will meet the UBC with wind rating of 85 mph
> and exposure C.
>
> Most of the crank-up towers are advertised with 70 mph ratings, but it is
> difficult for me to translate that to 85 mph, as I understand that the wind
> loading goes up exponentially. I would like to be able to handle about 15 sf
> of antenna on a self-supporting crank-up tower with 10 foot mast extended
> about 6 feet above the tower.
>
> With Tashjian Towers, for example, I can use their LM-354 HDSP which will get
> the yagi to 60 feet (54' tower plus mast). The only other option they would
> have would be the DX-86 with the top section removed, thereby bringing the
> tower down to 70 feet and the yagi to 76 feet. Using my calculations (not a
> formal bid), the higher tower would cost an additional $3000. (Their LM-470
> wouldn't be able to handle a 15 sf load at 85 mph/exposure C).
>
> How much more effectiveness, in terms of working dx, can I expect in going
> from an antenna at 60 versus 76 feet? I've played around with EZNEC and can
> demonstrate a decrease take off angle, but the difference doesn't appear
> dramatic. Hmmm.... is it worth the extra money??
>
> Thanks for your thoughts,
>
> Craig, AE7I
--
__________________________________________________________________________
Alan Zack
Amateur Radio Station K7ACZ
Las Vegas, Nevada, USA
Quality Engineer, The Boeing Company, Retired
Aviation Chief Warrant Officer, U.S. Coast Guard, Retired
U.S. Coast Guard, Always Ready, Always There
Every hour, Every day, Around the Clock and Around the World
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_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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