Antennas: Replaced comm antennas.

My left comm antenna has seemingly always been weak.  It's connected to the GTR 200, whereas the right comm antenna connected to the GTN 650 has consistently provided better performance.  So I measured the left comm antenna with my cheap vector network analyzer.  The left image shows the SWR (blue line), |S₁₁| (blue) and the complex S₁₁ (green).  The SWR is > 11 and the complex S₁₁ has a rolling phase and high magnitude.  Clearly, the matching network in the antenna is faulty.  

The right image shows the same measurement on a properly functioning comm antenna.  The SWR drops over the airband and S₁₁ is much more stable.

I ordered a new antenna from Delta Pop Aviation.   The new antenna is shorter with a more aggressive bend when compared to their older, as shown below.

My belly looks like the below after replacing the left antenna with that new one.  I wasn't too excited by the asymmetry (I guess I suffer from "airframe vanity").  

Delta Pop kindly sent me a new one for no charge to replace my broken one, even though it was 9 years old already. 

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.

Antennas: 1090 MHz ADS-B in antenna installed

My SkyRadar DX ADS-B provides ADS-B in on both 1090 MHz and 978 UAT, thus it needs two antennas.  Van's has a provision for a blade antenna on the right side of the airframe, behind the bulkhead (including another for ADS-B out on the tail).  I placed the SkyRadar's 978 MHz UAT antenna at that location, when I originally installed most of the antennas, since that antenna obviously should be downwards facing.

However, for the SkyRadar's 1090 MHz ADS-B in antenna, I spent a lot of time thinking about if I should put that blade on the top or bottom of the airframe.  There are good reasons to do both.  I actually wanted to put it on the top, however I couldn't stomach the aesthetics of a blade antenna sticking out on the top of the fuselage.  So I placed it on the bottom.

I printed out a template then carefully positioned it opposite the 978 MHz UAT in.  They both are about 1.25" from the inboard rivet lines.  This image is looking up at the bottom center of the fuselage.

I then got on my back and drilled the holes.  Aside from the headlamp I'm wearing, I'm not very visible in the image.  In fact, my friend, who's camping out in the baggage compartment (a.k.a., "economy seating"), is far more visible than I.

The antenna is then mounted.  You can see both of the SkyRadar ADS-B antennas in these shots, as well as the two comm antennas forward of the blades.

Avionics: Antennas mounted.

You can read about the antennas I'm using for my aircraft.

Per the EAA Hints for Homebuilders, I used DAP Alex Plus latex caulking to seal the antennas to the airframe.  It is a "siliconized latex" so it's paintable.  Here is an example of the bead of caulking placed along the perimeter of an antenna prior to bolting it on.  It dries clear and can be peeled away from unprepped surfaces.

This image shows the two comm antennas and one UAT 978 MHz antenna for the SkyRadar DX ADS-B in.

Here is the underside of the GA-35 GPS/WAAS antenna for the GTN-650 GPS/Nav/Comm.  The left image shows the routing of the coax.  I chose not to rivet in the doubler plate I constructed (center).  The side facing the top skin is not primed and primer was removed on the skin around the bolt holes to ensure a good ground connection.  More information on how I mounted this antenna can be found here.

Coax leading to the right and left comm antennas (top) as well as the SkyRadar DX UAT and GTX-330 ES 1090 MHz transponder antenna (bottom).  I plan to fabricate and add a doubler to the UAT antenna.  Although it's close to a rib, that skin is 0.025" and the blade can create significant torquing when slipping/skidding.

The GTX-330 ES 1090 MHz antenna.

The 1090 MHz ADS-B in antenna for the SkyRadar DX has not yet been installed.  I'm still deciding on where to place that antenna.  And the same for the Comant CI-158C-2 VOR/LOC/GS antenna for the GTN 650.

Antennas: Garmin GTN-650 GPS antenna mounted.

The Garmin GTN-650 GPS/Nav/Comm uses the Garmin GA-35 GPS/WAAS antenna.  This antenna must be located on the airframe.  I opted to place it behind the F-14126 Window and on the right of the F-01475 Aft Fuse Top Skin to clear the F-14131 Upper Aft Fuse Rib and F-01475A Skin Doubler, as shown with the red circle from page 10-1.

First a doubler needed to be fabricated.  The doubler template can be found here.  I used aluminum from an RV-9 capacitive fuel plate I had as scrap.  

A hole is drilled into the Aft Fuse Top Skin (and let me tell you, that was psychologically hard to do).  The antenna is then located, centered and temporarily affixed.  I happened to have a spare, "previously-flown" GA-35 I used for this purpose, so as not to mar my new one.

The four screw holes are then carefully matched drilled into the Aft Fuse Top Skin.

The antenna can then live happily in its new home.  When I permanently attach mine, it will need to include antenna sealant.

Go here to see how this was finally installed on 18-Nov-16.

Antennas: Antennas purchased.

The antennas for the bird have been purchased.

• Two 1030-1090 MHz Delta Pop transponder blade antennas
• One for the Garmin GTX-330 ES ADS-B and Mode A/S output
• Mounted under the tail in kit's provided cutout
• One for the SkyRadar-DX 1090ES ADS-B input 
• Mounted under the baggage area (an explanatory post will be forthcoming)
• One 978 MHz Delta Pop UAT blade antenna 
• For the SkyRadar DX UAT ADS-B input
• Mounted under the baggage area (an explanatory post will be forthcoming) 
• Two bent, Delta Pop lower mount, communications antennas
• One for the Garmin GTN 650 navigator
• Mounted at the bulkheads in the kit's provided right cutout
• One for the Garmin GTR 200 com transeceiver
• Mounted at the bulkheads in the kit's provided left cutout
• One Comant CI-158C-2 VOR/LOC/GS antenna for the GTN 650
• Mounted in the vertical stabilizer (an explanatory post will be forthcoming).
• One ELT antenna 
•  As part of the ACK-04 kit from Van's which includes the E-04 from ACK Technologies.
• Mounted behind the left seat at the window using the kit's mount.
• One GA-35 GPS/WAAS antenna for the in GTN 650 navigator (comes with the device)

Even though the stubby monopole transponder antennas are much cheaper, I decided to use blade transponder antennas since the empennage comes with a cutout for a blade UAT antenna.  I figure that's a better location for the ADS-B out as it's a high power transmitter (250 Watts) and I'd like it farther away from my other antennas.

Also, I considered putting one of the communications antennas on the top of the airframe, but opted against it as I felt it's a rare day indeed when one can't talk to the tower on the ground.

You can read about my mounting the GA-35 antenna and the others.