[NLRS] loop yagi driven element corrosion

[James Froemke]

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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