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Re: [TowerTalk] Antenna Pointing

Subject: Re: [TowerTalk] Antenna Pointing
From: Jim Lux <>
Date: Mon, 29 Aug 2011 08:41:47 -0700
List-post: <">>
On 8/29/11 7:45 AM, Mike Fatchett W0MU wrote:
> This question will bring about as many answers as how to find true
> north.  The problem is that the winds in a hurricane are changing so
> there would be no one good direction.
> On 8/29/2011 8:30 AM, Chuck wrote:
>> Just curious..... Now that Hurricane Irene has gone up the East Coast,
>> what strategies seemed to work best?  Did you point your beam into the
>> wind or broadside?  No hurricanes here in Iowa but quite a few storms
>> with high winds.

Or, just take the philosophy:  Wind speed rating is X mi/hr, independent 
of direction. (i.e. the mfr doesn't generally provide a "well, it's 
rated to 70 mi/hr along the boom, but 20 mi/hr crossways" kind of claim)

If the wind stays under X, there's a very small possibility of damage, 
regardless of orientation (assuming the mfr didn't stretch the truth). 
If the wind goes over X, there's a non-zero possibility of damage, and 
that's the risk you bought buying/building an antenna for X instead of 2X.

These are all probability and risk and the whole "pay more now for 
certainty, vs pay more later, maybe" thing

Say the antenna rated for 90 mi/hr costs $1000, and the antenna rated 
for 120 mi/hr costs $2000.

You plan to use those antennas for 20 years.

  If you get a 110mi/hr storm once every 10 years, your antenna cost 
over the 20 years is exactly the same: you buy 2 antennas for $1000 or 1 
for $2000.  If you get a storm every 20 years, you use the cheaper 
antenna, and accept the 5% probability in any given year that you'll 
need to spend another $1000. (i.e. it costs you $50/yr for the 20 years)

Yes, I know that hams aren't businesses, and don't do things this way.. 
you save up the cash, and buy what you can... but to put it in this kind 
of terms helps you to define your risk acceptance philosophy a bit more 
  explicitly.  I put up thin wire dipoles, knowing full well that it 
will come down in a strong wind, but also knowing that it's cheap to 
replace, and since we have no overhead power lines, the safety hazard of 
my thin wire coming adrift is small.  If I lived 20 miles from here 
where there is lots of overhead power lines, I might not make the same call.

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