18 May 2017

Antennas: VOR antenna installed.

Back, in January 2016, I cataloged the antennas I bought for the airframe.  Among those was a Comant CI-158C-2 VOR/LOC/GS antenna for the GTN 650.  

I had planned to mount this "cat whiskers" antenna on top of the vertical stabilizer, or even under the tail cone.  However, it turns out that fitting it on the vertical stab was very challenging.  And it couldn't fit under the tail cone as the latter has a j-stiffener running down the center.  So I needed to consider other options.

I'm not a fan of wing tip antennas as they are far from ideal. However, in this case, it appeared to be the best option.  So I went with an Archer VOR antenna.  This is an easy antenna to construct on one's own and that was my original intention.  However, when I added up what I needed to buy to make that happen, I decided that the opportunity cost of just purchasing the antenna was worth it.  Here is the product page from Archer.

Here is the antenna.  I will be placing mine on the right side as the left wing can't accommodate an additional run of coax as easily as the right.


Five nutplates on the wingtip needed to be drilled out.


The antenna is placed.  I put it far forward.


Nutplate holes are match drilled into the antenna.


There are two clips on the forward element of the antenna that help route the nav/strobe light wires in the proper location.  The screws associated with those clips also serve to affix the antenna to the wingtip.  I toyed with the idea of not drilling the holes for those screws and instead use wire tires through the clips.  However, I discard that idea in favor of using the screws.  To drill the holes, I needed to use my right angle adapter.  I used the unibit only because it could be chucked into the adapter.


Getting ready for riveting the nutplates.  Be sure to use soft rivets or, if those aren't available, don't fully set the hard rivets.


Here is the antenna finally placed.  The forward clips aren't yet in as the wingtip is not yet installed.  You can see that I also tacked the antenna down with some clumps of epoxy-flox.  They can be easily flicked off if the antenna needed to be removed at some point in the future.


The holes for the clips on the bottom of the wingtip are shown.  When I drilled those holes, chunks of gelcoat broke off.  So I needed to fill them and sand them down before countersinking for the holes.  Speaking of which, I used #6 screws for those clips.


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