[amsat-bb] Re: How best to park your satellite antennas

[Edward Cole]

At 09:16 AM 9/2/2008, i8cvs wrote:
>----- Original Message -----
>From: "Graham Shirville" <g.shirville at btinternet.com>
>To: <amsat-bb at amsat.org>
>Sent: Tuesday, September 02, 2008 6:35 PM
>Subject: [amsat-bb] How best to park your satellite antennas
>
> > Hi all,
> >
> > I cannot remember this question being discussed before!
> >
> > If you have a nice array of VHF and UHF antennas - 2 stacked X  8 foot
>long yagis one ach band plus a 2 foot S band dish, is it best from wind
>loading and other reasons to park it:
> > vertically pointing straight up (the dish has a hole at the bottom)
> > pointing to the horizon towards the prevailing wind
> > somewhere else?
> >
> > I know that at SSTL in Guildford they are usually parked pointing straight
>up but I have never been able to find anyone with a really good explanation
>for doing so.
> >
> > If you look at 193.51.07.114 you can see the sort of array that I am
>talking about!
> >
> > Many thanks
> >
> > Graham
> > G3VZV
>
>Hi Graham, G3VZV
>
>Pointing straight up with the main supporting boom in direction of the
>dominant wind is the best because the dish will offer the minimum surface
>to the wind while both yagi's are aligned in a way to be seen by the wind as
>about a single antenna.
>
>The above is my experience with less damages into the windy gulf of Naples
>
>73" de
>
>i8CVS Domenico

Generally, large radio astronomy or space tracking dishes are parked 
at zenith because this presents the smallest area exposure to 
winds.  Also, the dish load is balanced on its pedestal.  For a 
satellite array the long yagis present as much wind area as a small 
2-foot dish.  One could point the array directly into the wind but 
this would present the full area of the dish to wind loading.  If the 
array is pointed 90-degrees from the wind direction and pointed to 
the zenith, wind area would be minimized.

For my new 16-foot eme dish there is another consideration (living in 
Alaska).  That is snow loading.  A dish pointed straight up will fill 
with snow and rain definitely overloading it.  The best stow position 
is on the horizon and pointed 90-degrees to the prevailing 
wind.  Large dishes should have tie-down wires for further 
stablization in high winds.

So it varies with the situation and type of antennas.  The idea is to 
minimize wind area.


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73, Ed - KL7UW              BP40iq, 6m - 3cm
144-EME: FT-847, mgf-1801, 4x-xp20, 185w
http://www.kl7uw.com     AK VHF-Up Group
NA Rep. for DUBUS: dubususa at hotmail.com
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