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Installing GDL-82 In Completed RV-8

ArlingtonRV

Well Known Member
I just completed the installation of a GDL-82 in my 2001 RV-8 (I'm not the builder). The good news, I just completed the validation flight and have all green and got the Incentive Code to apply for the rebate. The bad news, I started all this on December 22nd.

The long span is all my fault and the result of a few things, 1) even though I thought I panned ahead to have everything on hand, I still needed to order a few things, 2) I planned to do it over the holidays so getting the things I forgot took longer than usual to get, and 3) I had no idea where I wanted to mount everything and spent a lot of time working out logistics.

This is simply intended to show what I did. It works, so it is a viable option, but not necessarily the best or only option.

The first consideration that took a lot of time to resolve was where to put the GPS antenna. I have a Garmin GNC 250XL so there is already a GPS antenna on the turtle deck. I considered putting the new one next to and farther aft of the one that is there, but to maintain the 9" minimum, 12" preferred distance between antennas that idea became untenable.

I then considered replacing the 250XL antenna with the GDL-82 antenna and just living without GPS on the 250 XL (I have an Aera 660 and an iPad running Fore Flight), but I didn't really like that idea. I also considered replacing the 250 XL antenna with the GDL antenna (they use the same hole pattern) and using it to provide GPS data for both units using a splitter. The problem there was more wires to run, another piece to mount and another $300. I ended up using the antenna shelf from the RV-12 (current part number F-01201R-1) on the firewall and mounting it there. When complete, it looked a lot like this:

IMG_2008-L.jpg


The next issue was where to mount the box itself? I spent a lot of time on this one. Some of the areas that I considered but ultimately rejected are: under the front seat, on the rear baggage shelf, on a shelf behind the rear baggage bulkhead, and inside the forward baggage area.

What I finally settled on was on the rear (cabin side) of the aft bulkhead in the front baggage area which is behind the instrument panel. It looks like this:

IMG_2023-L.jpg


This was reasonably easy to get to, was convenient to other wiring, didn't cost baggage space in the forward hold, and has it out of sight. The excess coax from the GPS antenna (6.5' minimum) is easily coiled up and secured out of the way.

Since the original transponder (GTX 320) had RG58 coax from the transponder to the antenna I had to replace that with RG400 as well. There was no problem getting 6.5' there, once routed it was actually more than a foot longer than that.

Once I figured out where to put everything the installation wasn't that hard (just a lot of crawling in and out of the airplane and under the panel).

I want to give a solid shout out to the folks at Stein Air, and particularly Christer Stenstrom, for answering all of my questions.

I also want to thank the previous owner, Carl, for his help in getting this installed.

More pictures can be found here: https://steverush.smugmug.com/GDL-82-Install/
 
Nice job.

Mounted my GDL-82 in pretty much the same spot. Mounted mine a little higher on the bulkhead which turned out to be a pain as it put the top mounting bolts to close to the formed lip. Made installing hardware and tightening a bit of a pain but worked out.

Didn?t know the antenna could be oriented that direction.

Passed my maneuvers fly off and filed for my rebate. Not sure how well that?s going to work out with the government shutdown.
 
So the GPS antenna ends up under the fiberglass cowling and can't be seen unless the cowling is taken off, correct?
 
GDL-82 Install

Steve,

Regarding placing the GDL-82 antenna on the turtle-back in the spot of my existing antenna....the hole pattern is the same on my RV-7A as well...Do you mind explaining the use of a splitter, additional wire to run, another piece to mount, and another $300 bucks?

The GDL-82 antenna on my setup would have to connect to both my Garmin 495 and the GDL-82 using the splitter. But what is "the other piece to mount" that you are talking about?

Any additional info on this would be greatly appreciated and thanks for posting your install on your RV-8.

Thanks,
Dan "Cuzz" Roy
RV-7A
 
Installation in an RV8 with a Showplanes canopy kit is closely related to the under-cowl antenna placement.

A Showplanes -8 has a fiberglass glare shield covering the avionics, another glare shield in the canopy frame, and of course the plexiglass. The GPS and XM antennas seem to treat all that plastic as invisible.

I have a standard GPS antenna, an XM antenna, and the GDL82's GPS antenna all in a row, on a shelf directly above the EFIS. Please be aware the antennas are too close to each other per Garmin's instructions. That said, the FAA flight report was all zeros, no issues at all.

The GDL82 box is seen just forward, on the cockpit side of the baggage wall.

GDL-82%20Component%20Placement.jpg
 
Garmin does not recommend using a splitter on the GPS antenna. I would strongly suggest following this guidance.

Garmin also does not recommend mounting the antenna below the cowling or too close to other GPS antennas. However, we have seen many installations that work well in these scenarios. There are two potential issues with mounting the GPS antenna under the cowl. The first is heat and the second is the cowling. The fiberglass will not block the GPS signal, but we cannot control how much or what type of paint is on the cowling. This could affect your signal. Each engine installation will have different levels of heat under the cowling. Your antenna may work in this location for a long time without any issues. If you do mount the antenna under the cowling, the signal will be shaded by the firewall, so you would want the antenna as high as possible.

Dan Roy, In your installation, you could put the antenna for your 495 on your glareshield and the put your GDL 82 antenna on the turtledeck. As mentioned above, I would use separate antennas for these products.

Thanks,
Levi Self
 
DanR, because you asked, I was referring to this splitter.

https://www.gpssource.com/collectio...MI9qvM_s2J4AIVhB-tBh1olA8YEAYYAiABEgJNE_D_BwE

It was used in this thread.

http://www.vansairforce.com/community/showthread.php?t=167004&highlight=splitter

I didn't want to pay another $300 for the splitter and have to worry about where to mount it, etc. I was also concerned about signal degradation feeding two different units. Based on comments from Levi, that concern seems to be valid.

The extra wire comes from having one input and two outputs. Using just the antenna per the Garmin instructions you have one cable from the antenna to the GDL. Using a splitter you would have to have a cable from the antenna to the splitter, then a cable from the splitter to the GDL and another from the splitter to the existing device (250 XL in my case).

After thinking through all of that I opted not to use a splitter.
 
GDL-82 Install

Steve,

Copy all. I do have a clear understanding now regarding the splitter, etc. Thanks for taking the time to dig out the previous VAF post and splitter part photo and part number.

I think the easiest, best, and quickest way to install the GDL-82 on my RV-7A is exactly the way Levi stated in his post.

Have a good one & glad your 8's ADSB is up and running!!

R,
Dan
 
Install complete

I installed the GDL 82 last weekend and finally got to fly in ruled airspace
today. No issues with the install or the validation flight. With the rebate code and the incentive code
from the GAIRS report, applying for the rebate only took a few minutes to complete. I purchased the GDL 82 from Spruce
because for +$24 it comes with a pre-wired 10 ft. harness. Just having the USB connector wired was worth it.
My ADSB in unit is a GDL 39 that is blue-toothed to my panel mounted 796 and a Ipad mini 4. Although I've had the GDL 39 for awhile,
now with the out solution lighting up ground stations all of the time, the amount of TIS-B traffic shown
on the 796 and ipad is amazing (here in the LA basin). I mounted the GDL 82, like the previous poster,
on the access panel on the rear bulkhead of the forward baggage compartment of my -8A. Total cost including cables, fault lamp,
CB and the RV-12 shelf for the GPS antenna mounted on the firewall was right at $2,200.

GDL%2082%20install-M.jpg
 
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