[NLRS] loop yagi driven element corrosion

[John Toscano]

Actually, I think that the DE is brass, not copper. But in any event, not
aluminum like the rest. ;*)

On Wed, Sep 14, 2016 at 9:05 PM, James Froemke <jim.k0mhc at earthlink.net>
wrote:

>
>
> The driven loop is copper. Send a note with a picture to Terry at his
> Directive Systems e-mail address. He gives great customer support.
> 73, Jim
>
> > On Sep 14, 2016, at 8:56 PM, Chris Elmquist <chrise at pobox.com> wrote:
> >
> >
> >
> > I've mentioned this to a couple guys and am kind of perplexed about this
> > issue...
> >
> > I have two DEMI / Directive Systems loop yagis on my tower at about the
> > 35' point.  One is 33 elements on 902 and the other 45 on 1296.
> >
> > While doing some work on other antennas on the tower, I noticed that
> > the driven elements on both of these yagis are extremely discolored
> > (ie, black).  All the other elements on both yagis are nice and shiny
> > aluminum color.
> >
> > The little rigid coax that comes down to meet the N feedpoint connector
> > from the driven element is also black on both yagis.
> >
> > The yagis a fed with a length of Superflex that goes down the boom to
> > the mast, down the mast a few feet forming a rotor loop, and then
> > meet a run of 7/8" Heliax (air line under positive pressure).
> >
> > These antennas seem to still work as well as when they were put up but
> > I'm concerned about the discoloration since it suggests some kind of
> > dissimilar metal action or some other kind of active attack against the
> > metals--  but I'm not sure where or how that would be happening.
> >
> > And no, I'm not running 1 KW+ on these bands :-)  30W on 902 and 60W
> > on 1296.
> >
> > Tower is aluminum and all these feedlines are copper of course but
> > all jackets are still intact and no copper is meeting the aluminum.
> > Everything's taped and sealed really well and so I'm having a hard time
> > explaining what process would cause the entire element to turn black
> > with no similar situation occuring on the other elements, boom or other
> > non-loop yagis on the tower.
> >
> > Any ideas?
> >
> > Chris
> > --
> > Chris Elmquist N0JCF
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