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Re: Antenna Dish

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As additional information, I worked with Mercury and Marconi in the UK on
expanding existing earth satellite stations, which this sounds like. They
typically supplied all the forces and serviceability requirements (maximum
allowable twist/tilt at lower wind speeds vs. surviveability at higher wind
speeds).

James Cohen
James Cohen Consulting, P.C.
PO Box 130
Pennington, NJ 08534
Tel: (609) 730-0510
Fax: (609) 730-0511
Website: http://u2.expertpages.com/jccpc


----- Original Message -----
From: "T. Eric Gillham PE" <teric(--nospam--at)gk2guam.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Wednesday, March 07, 2001 22:56
Subject: RE: Antenna Dish


> THANKS so much for all the input.  This helps me to remember why we have
> this list, and how valuable it is to me.  I am currently working on
getting
> a copy of the ANSI/TIA/EIA-222-F-96 standard, which I THINK I can get
> electronically from Global Engineering something or other (thanks James
> Cohen from NJ). I think that will give me the insight I need, although
many
> if not all of the suggestions/opinions furnished by listserver members has
> been very helpful.
>
> Thanks also to John Maclean for the faxing offer - I may take you up on it
> if I can't get the standard mentioned above.
>
> If anybody wants to know, this isn't the first dish put up here - it is
> going to be one on a sort of "farm" that we have down at the
> central/southern part of the island.  Some of the other dishes are even
> larger, and are used by MCI among others for telecommunications.  This
> particular dish will be used for satellite tracking.
>
> In answer to Roger's questions below - I believe it is standard practice
to
> put these dishes in a locked "typhoon" position prior to storms.  My bet
is
> they cost plenty, and the poor sap who forgets to lock it down will be
> paying out the you know what for a long while.  I don't believe it is
> possible to (economically) construct a dish that will withstand our winds
> (recorded at 155mph+ on a number of occassions in the last 30 years or
so),
> so locking it in position is the only way to go.
>
> I am going to get the standard, and see if it offers any concrete data wrt
> to design approaches.  If not, then I will take the manufacturer's OTM,
> bring it up a bit, then take the make it stout approach.  What makes it a
> bit easier is that the UBC94 calcs, crude as they are, come pretty close
to
> the manufacturer's OTM. In all likelihood, I think the antenna will be
> ripped apart before it overturns, which from my perspective (since I
didn't
> design the antenna itself) is my main concern.
>
> Thanks again all.
>
> T. Eric Gillham PE
>
>
> -----Original Message-----
> From: Roger Turk [mailto:73527.1356(--nospam--at)compuserve.com]
> Sent: Thursday, March 08, 2001 12:12 PM
> To: seaint(--nospam--at)seaint.org
> Subject: RE: Antenna Dish
>
>
> Eric,
>
> The questions that I have are:
>
> At what conditions (wind speed, etc.) will the antenna be pointed straight
> up?
>
> Are the locking pins inserted manually or remotely?  If manually, what is
> likelihood of nobody willing to mount the antenna in an approaching
typhoon
> to
> insert the pins?
>
> Are the people using the antenna constantly aware that the antenna should
be
> pointed up when a typhoon approaches?  What are the chances that they
would
> forget?
>
> I think that the answers to these questions would indicate how the antenna
> should be positioned for design.
>
> I have been asked in the past to provide design calculations for small,
roof
> mounted parabolic (satellite) antennas.  I have requested the
manufacturers
> to
> provide me with the projected wind area and center of pressure locations
for
> the antennas and never received any information.  Without this
information,
> I
> would be hesitant to design supports for antennas subjected to wind loads.
>
> Hope this helps.
>
> A. Roger Turk, P.E.(Structural)
> Tucson, Arizona
>
>
>