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Garmin GDL 82 ADS-B

bobg56

Well Known Member
I'm trying to figure out what kind of device to get for my 2010 RV12, either the GDL 82 or Sky Beacon, the GDL 82 antenna placement has me concerned. I would like to place it under the engine cowl next to my GPS antenna that would be easier but would it create problems? Or the Sky Beacon, has anyone put these on their RV 12's? ...The Sky Beacon seems the simplest but simple sometimes has issues, I can use some advice...thanks.
 
I recently installed Uavionix Skyfi-EXT in a friends RV6. Installed the GPS on the turtle deck and spike on the belly. Works great and in in and out. Passes the FAA test.
You may find a difference in the required GPS reception for ADSB versus navigation requirements.
 
Now to figure out what to buy that will work the best and easy to install...
 
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Installed the GPS on the turtle deck and spike on the belly.
In the RV-12, I agree that the turtle deck would be the theoretically-best place for the GPS antenna due to the large ground plane. Unfortunately, the installation seems problematic. To gain access, I understand you have to remove the gas tank and the rear bulkhead. My RV-12 buddy is contemplating installing a GDL-82 and really doesn't want the installation to become a major project. The next best option (electrically speaking) would be on top of the deck in front of the canopy. It might be visually offensive in that location, though. Although it violates all the guidelines from Garmin, I guess I'll advise him to put the antenna in the engine compartment like others have done successfully.

Regarding the spike antenna - since you will be broadcasting on both 978 MHz and 1090 MHz you will have better performance with a broadband "blade" antenna like the Comant or Delta Pop. Both are available from ACS.
 
I purchased the GDL-82 with GPS kit, no instruction manual or coax cable included. I did see the instructions for the Mooney install, should I use these instructions? and what about the cable length for the GPS antenna, is there a minimum length?...I thought the kit would have all instructions and needed cable, a little disappointed but I can get the cables made that I need...anyone who has already put one of these in your RV12, I sure could use your help...thanks, Bob
 
This is the install manual I used.

https://m.aircraftspruce.com/catalog/pdf/gdl82install.pdf

I ordered my unit from Stein Air since I knew I would have a lot of questions and they were very good about answering them for me. Based on information from Stein, the coax should be RG400 and between the GPS antenna and the GDL-82 should be 6.5 feet minimum. The run from the transponder to the transponder antenna should also be 6.5 feet minimum. The run from the GDL-82 to the transponder is not length limited and can be any length. Any excess cable can just be coiled up and secured wherever it is convenient.
 
Minimum length of RG400

Would sure like to verify that the RG400 cable must be minimum 6.5?. I?m planning minimum distances between the GDL82 unit and the 1) existing transponder antenna currently between the main gear and 2) the newly installed gps antenna which I anticipate placing on the tip up glare shield. Both of these coax runs will be much less than 6.5?. Is coiling the coax to achieve 6.5? necessary?

Jim Diehl 7A
Lock Haven, Pa
 
I'm looking at placing the unit inside the forward area where all the other avionics is located, close to the transponder, that will be a shorter cable, but I'll have to coil the 6.5', then mount the GPS antenna under the engine cowl next to the GPS nav antenna..other guys have said that works.
 
The run from the transponder to the transponder antenna should also be 6.5 feet minimum. The run from the GDL-82 to the transponder is not length limited and can be any length. Any excess cable can just be coiled up and secured wherever it is convenient.
Thanks for the new revision (Rev. 5) of the installation manual. I used Rev. 3 and I see some differences, like the size of the ground plane, for example. You have me confused with the above quote, though. The manual Rev. 5 Section 4.5.1 says "The GDL 82 should be mounted as close as possible to the antenna to reduce the length of coaxial cable between the unit and the antenna." (I used a 24" length of RG-400).
 
Would sure like to verify that the RG400 cable must be minimum 6.5?. I?m planning minimum distances between the GDL82 unit and the 1) existing transponder antenna currently between the main gear and 2) the newly installed gps antenna which I anticipate placing on the tip up glare shield. Both of these coax runs will be much less than 6.5?. Is coiling the coax to achieve 6.5? necessary?

Jim Diehl 7A
Lock Haven, Pa

I'm no expert and don't really know what I am talking about, I am merely regurgitating what I have been told. The GDL-82 installation manual page 6-7, Table 6-3 states the minimum and maximum acceptable GPS dB loss. From that, I was working to the 1.5 dB minimum. Page 6-8, third paragraph under 6.4.1 states "For RG-142B or RG-400 coaxial cable, 1.5 dB equates to a length of approximately 6.5 feet of cable with a connector on each end."

That is where the 6.5 feet comes from and, was verified by Christer at Stein Air. Will a shorter cable work? You'd have to ask someone who knows what this all means.

https://m.aircraftspruce.com/catalog/pdf/gdl82install.pdf
 
I spoke to Garmin and was told that the antenna to the GPS needs the 6.5' min. to get that 1.5 loss that's needed. The GDL-82 needs to be close to the Transponder antenna like as what's shown using the C-172 drawing...my question to those who have installed one in an RV did you deviate and put the unit behind the instrument panel? Did you use less than 6.5' of coax to the GPS antenna and lastly did it work?...My Transponder Ant. is just forward of the steps, it looks like the center angular area between the seats is where I may put it so its close to the antenna...I'm still trying figure out the best way, any proven methods will help greatly, thanks to all for the suggestions.
 
Bought my GDL82 and all,cables from SteinAir. Mounted the GA35 antenna under the cowl. Had SteinAir fabricate the cables. Well worth it. Mounted the GDL82 box behind the panel close to the GTX327 transponder. Easy install and I?m not good at this stuff. Worked without flaw the first time I powered it up. I highly recommend buying everything you need from SteinAir. They know this stuff and can answer all questions.
 
How difficult was it programing it with lap top? The instructions tell you to go to Garmin and download the installation tool....I read through it in the install manual, seems a bit confusing.
 
Actually, the most difficult part of the programming, for me, was finding the stupid install tool. I couldn't find it on Garmin's web site so I just Googled it. It can be found here: https://www8.garmin.com/support/download_details.jsp?id=12839.

The second problem I had was my USB cable. For whatever reason the first one didn't work. I got another one and I was able to get the laptop connected. Once connected the actual setup is straight forward. There are a few pieces of information to enter (Tail #, type, existence of ancillary equipment, etc.) and then doing a series of transmit tests to ensure no interference from the comm radio.

Once connected I think the whole thing took maybe 15 minutes.
 
Thanks for the info, when it comes to software updates and such I cringe because usually its like opening Pandora's Box...I have my software up to 5.6 instead of Vans 5.5...that's because I sent a servo to Dynon for repair and it came back with 5.6, it's a long story but it left scares on me so anytime it comes to a laptop I get nervous, I'm not an idiot I can think but I went down the rabbit hole trying to get everything squared away and it is now, I'm just hoping this ADS-B thing doesn't give me an ulcer...thanks again!
 
A few final ADSB questions

Alas, I ordered the GDL82 through a local avionics shop. I?ll do the install while they?ll cut the coax cables to size and install the end connectors and help with the data download.
I?m currently using a monopole AV22 transponder antenna that appears incompatible. How about the rami AV74 (not on the garmin list)? Any antenna recommendations that don?t rob the bank!?
...and to clarify, 1) the coax to the gps antenna should be 6.5?. 2) the coax from the gdl82 to the L Band transponder should be 6.5? (or less?). 3) keep the coax from the Garmin 327 to the GDL82 a short distance.

Thanks,
Jim Diehl 7A
 
I believe that the shorter coax is between the GDL-82 and transponder antenna, similar to the diagram showing the Cessna layout.
 
GDL 82 install into an RV-7

Bob, interesting topic. I too am installing a GDL 82 but into my RV-7. I went with the antenna shelf under my engine cowling for both the GNC 250XL and the GDL 82 GPS antennas. I have one final question. Which USB pigtail wire color did you plug into the J821 pin #6? I have found (with a google search) that sometimes the USB green wire is D+ and sometimes its D-.
 
This is what I did regarding USB pin#1 is white..#6 green...#7 Ground...#11 Red...I'm installing it in the next few days...
 
Coax to L-Band Transponder

Bob, I did call Garmin regarding the length of the 400 coax cable from the GDL82 and the required L-Band transponder antenna. They said "as short as possible". I told them I was putting the GDL82 in the avionics bay 6 to 8 feet away. Two tech's at Garmin said "OK". Both tech's gave a long pause before they would say "OK" Hmmm... John
 
I've heard a few guys say they put it there, and put the GPS antenna next to the Nav GPS antenna under the engine cowl and it worked fine. I have not started my installation yet. I thought of putting the unit in the tunnel area close to my xponder antenna but I'll have to open it up to see if it will have clearance there.
 
. . . I have not started my installation yet. I thought of putting the unit in the tunnel area close to my xponder antenna but I'll have to open it up to see if it will have clearance there.
Same here.
The closer to the L-band antenna . . the better.
 
Getting ready to do the GDL-82 install. How do you tie into the Avionics master switch for a power source, the switch is mounted to a circuit board...I'm not the builder so I don't have any wiring diagrams. Thanks...Bob
 
You can connect the GDL-82 power lead to the Xponder Circuit Breaker.
That is what I did. My xponder breaker was 3 amps. The GDL-82
needs a 5 amp breaker. So I replaced the 3 amp breaker with
a 10amp. Download the GDL-82 install manual (the unit doesn't come
with the install manual). All the info you need is in the manual.
 
I have fuses that are mounted in a circuit board, not CB...I'm thinking of tying into the #1 pin wire on the connector that goes to the transponder, that's the power wire according to the print..
 
Unit is installed in Avionics compartment just forward of Fuse panel, I added the "Failure" light feature, which will light up when in the hanger. Finding the Garmin install tool was a bit challenging, what I had saved on my desk top was NOT the install tool, that was located in my C drive, that confused me so I needed to call Garmin about finding it, I have Windows 10...that could have been made easier if explained in the install manual. After getting the plane outside on the ramp everything fell into place, now or the verification flight.
 
You can connect the GDL-82 power lead to the Xponder Circuit Breaker.
That is what I did. My xponder breaker was 3 amps. The GDL-82
needs a 5 amp breaker. So I replaced the 3 amp breaker with
a 10amp.


Whoa there....

The typical transponder is wired with 20ga, good for 7 amps at 35C rise. Unless you have some heavier wire in there (unlikely given the d-sub termination), a 10 amp breaker has the potential to turn the wiring into a fusible link. Same for the GDL-82 power lead.

A 10 amp breaker is unnecessary anyway. See page 2-2 in the GDL-82 install manual. Power draw is 0.5 amps max with the companion GPS, not 5 amps, which is just the breaker size shown on the drawings...probably because of the expected wire.

I don't know what you have, but for example, power draw for a GTX-327 is less than 2 amps.

Assuming both are wired with 20, go back and swap in a 5 amp breaker for the transponder and GDL-82 combined.
 
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The install is complete, ground checks done, flt. check done and passed...rebate on it's way, ADS-B compliant! Sweet!
 
Bob, I am getting ready to install a GDL 82 in my RV 12. Did you mount your GPS/WAAS antenna on the shelf beside your Garmin 496 antenna?
 
You can connect the GDL-82 power lead to the Xponder Circuit Breaker.
That is what I did. My xponder breaker was 3 amps. The GDL-82
needs a 5 amp breaker. So I replaced the 3 amp breaker with
a 10amp. Download the GDL-82 install manual (the unit doesn't come
with the install manual). All the info you need is in the manual.

Careful, the breaker is to protect the wiring, not the equipment. What is the gage of the wire you have to the transponder?

oops, I see DanH already responded.
 
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Yes Mike I did mount them next to each other, but I had to make a larger mounting plate for both. Also I had to tap into the red (pin #1) wire on the Transponder plug to get power to my Failure Light and unit since the switches are mounted in a circuit panel. It all worked out great. You'll have to search your lap tops C drive using "GDL" to get the install tool up on Windows 10 to program the unit with a few numbers....good luck
 
Finished my install and test flew yesterday--passed! 44 mins in LAX mode 'C' veil. Configuration no problem, also had my GTX 327 software updated from v. 2.10 to v. 2.13 (thanks Howard Aviation at KPOC). My PAPR report showed 14 seconds of 'air on ground', I checked the FAQ on the FAA's ADSB webpage and found that too low of stall speed entered in the GDL 82 configuration will cause this. I'm below the threshold that would cause a failure to pass the flight test, but I'm going to change the calibration to bump up the stall speed anyway. Easy enough to do. I installed the GDL 82 behind the baggage area on the floor. GPS antenna on the turtledeck almost directly above the unit, 'Shark fin' L-band antenna at the rear of the fuselage, all connected with RG-400 cable. No interference issues with the GTR-200 comm, CreativAir strobe pack, or ancient Lowrance 2000C GPS. Looking forward to getting an Aera 660 with the help of the rebate. Had fun doing the maneuvers during the flight test, including pushing the nose over to get to 200 mph--didn't take much to get it there---also did a couple 360s at 1.3 Vso full flaps--love the speed range of all Van's planes.

Greg RV-9A N4603X
EFII 0-320-H2AD
Catto 3 blade
 
Thanks, sounds like my installation will be almost identical to yours. Glad to hear it is working.
 
Garmin Gdl82 question

I have my GDL-82 wiring ready to install but it hasn?t been configured with the software installation tool, and the external gps antenna is not yet connected. However the transponder output is connected to the GDL-82 and its output is connected to the ads-b out antenna. My question is whether the GDL-82 will pass the transponder signal to the adsb out antenna, even though the GDL-82 is not configured and doesn?t have its gps antenna connected. I want to fly before everything is finalized, but will need the transponder out signal. Yes, I could just connect the transponder directly to the out antenna, but that requires more under the panel crawling.
 
Maybe Garmin will jump in here. When I was doing mine and wanted to do the same thing was told it would do damage.
Pulled the GDL-82 antenna leads out of the system to fly per Garmin.
 
Maybe Garmin will jump in here. When I was doing mine and wanted to do the same thing was told it would do damage.
Pulled the GDL-82 antenna leads out of the system to fly per Garmin.

I hope they do. What would it damage?
 
Garmin GDL-82 ADSB

It seems highly unlikely the GDL-82 would be damaged because its GPS input antenna is not connected. What I am asking is whether the GDL-82 transmits the transponder data it receives, even though the GDL-82 does not have its gps antenna information. In other words does it default to re-broadcast of the transponder mode C data, or just remain silent?
 
I have my GDL-82 wiring ready to install but it hasn?t been configured with the software installation tool, and the external gps antenna is not yet connected. However the transponder output is connected to the GDL-82 and its output is connected to the ads-b out antenna. My question is whether the GDL-82 will pass the transponder signal to the adsb out antenna, even though the GDL-82 is not configured and doesn?t have its gps antenna connected. I want to fly before everything is finalized, but will need the transponder out signal. Yes, I could just connect the transponder directly to the out antenna, but that requires more under the panel crawling.
Hello John,

It wouldn't be wise to operate the GDL 82 (apply power) and fly with it without having it configured or having GPS data.

As explained in this posting, when a transponder is connected to a GDL 82, it should be considered one system which must all be working for any guaranteed performance. There is no guarantee that your transponder will meet its design requirements when the GDL 82 is not operational.

If you want to fly now and use the transponder without the GDL 82 being fully operational, you should re-connect the transponder antenna to the transponder and keep the GDL 82 unpowered.

Thanks,
Steve
 
It wouldn't be wise to operate the GDL 82 (apply power) and fly with it without having it configured or having GPS data.

Thanks Steve. I think he was asking about operating the transponder with the GDL-82 unpowered. "Guaranteed performance" aside, would doing so damage something?
 
Garmin GDL-82 adsb

Let me ask a simpler question: Assume the Gdl82 is powered up. What does the gdl82 do when there is a loss of gps signal (a loose BNC gps antenna connector, water in the connector, etc.) ? Does it still pass (re-transmit) the mode C information from the transponder? Or does it go silent, or do something else?
 
Garmin GDL-82 Adsb

And also do you have an answer to Mr. Hortons question about th unpowered GDL-82 ?
 
Pass through

I flew mine with the GDL-82 unpowered for one flight. I called up a local tower controller and he confirmed a good transponder reply. I wanted to confirm that my Becker transponder would work with the GDL-82 before trying it with the GDL powered up. The antenna connection goes straight through. I see no reason you can?t fly that way indefinitely.

-Andy
 
]I installed the GDL 82 behind the baggage area on the floor. GPS antenna on the turtledeck almost directly above the unit, 'Shark fin' L-band antenna at the rear of the fuselage, all connected with RG-400 cable. No interference issues with the GTR-200 comm, CreativAir strobe pack, or ancient Lowrance 2000C GPS.

Greg RV-9A N4603X
EFII 0-320-H2AD
Catto 3 blade

Sounds like a good installation, anyone out there in an RV-8 doing something similar? I'm planning for either the GDL-82 to go with my GTX-327 Transponder or perhaps the Tailbeacon for an easier install.

Can anyone comment on the Tailbeacon vs the GDL-82 in terms of user experience, or pros and cons? The installation is the only con on the GDL-82 it seems at this point. Thanks.
 
install photos?

The install is complete, ground checks done, flt. check done and passed...rebate on it's way, ADS-B compliant! Sweet!
Can you provide any photos of your install. Getting ready to do the same, but cant decide where to put everything. any help would be greatly appreciated.
 
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