On 22 Feb, 17:31, "JIMMIE" wrote:
On Feb 22, 7:41 pm, "Lex-Lutor"
wrote:

What will be the best material for log-periodic antenna design, my idea is
to build LP-ant. for 14-30 MHz but it must stay alive at wind over 120 mPh.
Wellding and machine work is not problem bigest problem is to select good
Aluminium?

Maybe AA6082 or AA6061 something elese ?

Thanks for any help or info ?

aluminum double boom, fiberglass elements, just a thought.

Jimmie

The biggest problem here is the number of elements and it's support
system The high winds excabate the problem since that requires a
willow tree function of bending in the wind The support system suffers
because of the plan view where all the longest elements are at one end
which is probably why many are made of simple wire Obviously you must
find the lightest material suitable for the use and apply a skin of
aluminum to the elements
of your choice. If you are uneasy about the rigidity of the assembly
then a non electrical member circling the whole array should suffice.
Personally I would avoid welding because of added weight and failure
initialisation and if possible extend the elements with non radiating
materials to defrock the damaging winds upon the rotor.Another factor
would be the use of a tapered element that does not provide a stopping
point for ice especially because of the number of elements. Better to
be a natural taper such that ice formation falls off at the ends.
Ofcourse you can change the design to elements that slope so it can be
used on two bands or even apply solenoids to the skin for extra band
use.
Solenoid could be made using thin medical syringes with a few lays of
wires and a metal nail insert to make the connections from the inside
of the element, this way weight addition is minimal. It may upset
people people on this group if I mention fishing poles but I mention
that because I have made 13 element yagis on a 60 foot boom in the
past and I am in the Midwest which is quickly being inhabited by
swarms of windmills to take advantage of the perenial winds except
when we have ice storms!
Poles are available on E bay in quantities of twenty or more for 20
foot length at less than $10 a pole which is very economical compared
to aluminum and they are also telescopic and will bend and not break
if you catch a big fish coated in iced.
Art