[TowerTalk] Antenna Survivability

[Jim Lux]

At 07:39 PM 6/15/2005, WarrenWolff at aol.com wrote:
>When checking out which antenna will survive the  harshest
>of threats, pay all the attention to the experienced  fellows
>on here----not the manufacturer.
>
>Years ago, I had some fancy UHF antennas put on top  of
>100 meter towers in Kuwait.  Only rare, really rare,  times would any ice at
>all show up there, but the wind blows.  These  antennas were
>rated at 100 mph by the US  manufacturer.  After just a few months,
>we found a piece of aluminum element on  the ground - - - more to
>follow in days.
>
>The Minister of Defense requested/demanded that I produce  test
>sheets from the manufacturer to verify that I/we had not  short
>changed them!  Well, they did NOT have any.  They  had put these,
>the ruggedized versions, together by the seat of their  britches.

This is, in general, true of all things sold into the amateur/consumer 
market.  The price isn't high enough to pay for real testing, even of a 
preproduction prototype. I cringe to contemplate what it would cost to do 
wind survival testing for a HF antenna.  Even doing it the "cheap way": 
bolting it on the back of a flatbed truck and driving into the wind at a 
sufficiently high speed.

The only practical alternative is to see design calculations that shows 
that if manufactured properly, it will stand up. And then, you have to have 
sufficient "visibility" into the manufacturing process to tell if it is 
doing what's expected.  On commercial construction projects, for instance, 
they require certified welders, and sometimes require X-ray inspection of 
critical welds, as well as test coupons.  Likewise, that's why they take 
samples of the concrete from the truck for testing.

Most manufacturing tests for consumer equipment is more in the nature of a 
functional test, rather than a performance test.  That is, does it light up 
when you apply power? Do some of the buttons work?  And if they do a 
performance test, it's unlikely they'd supply the test results (or even the 
test procedure, for that matter) to the eventual purchaser. For most 
manufacturing companies it would be a trade secret anyway.

So this is why it's wretchedly expensive to buy things for airplanes and 
spacecraft. Those buyers tend to be a bit more demanding and less trusting. 
They want to see "physical artifacts" of the manufacturing and test 
processes: documentation of processes; documentation of test results; etc.

>
>Bottom line; I had to replace/rebuild them at my cost.   Manufacturer
>would not stand behind them according to my Purchasing  Dept.  I
>had to pop for $1000 per antenna times two per tower times  10
>towers.  My company?  Lockheed Aircraft Service Co;  the supplier?
>Phelps-Dodge, if I recall correctly.  My chief engineer  has passed
>on or I would ask him.  Probably a mute point now; Saddam  stole
>the whole system.
>
>Good  luck in your survey,  Warren;  W5KKW