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Garmin GDL 82 ADS-B

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.


Except that it's not legal. The ADS-B regulations state that if an aircraft is equipped with ADS-B out the equipment must be functional and turned on any time the aircraft is operated. That includes taxiing on the ground in Class G (middle of nowhere). Make sure you or your mechanic has the GDL-82 (or any other ADS-B out device) "on" during maintenance test runs or taxiing to the gas pumps. Those activities are operations.
To do otherwise risks a violation. Is it logical or reasonable? No. On both counts. But unfortunately it is the current FAR regulation. So the FARs stipulate don't ever turn it off for any reason anywhere (accept for formation wingmen with coordination with ATC). ��
 
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Unpowered GDL 82 and Canada

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 was wondering about this. Secton 8 in the install manual doesn't include any performance check with the GDL shut down, so not sure what to expect.

The December issue of Kitplanes has a write up on ADS-B and Canada. If I understood things right, for below 12.5k, there isn't a concrete plan or a schedule for ADS-B, so mode C will certainly be fine for a while, yes?

What to do with the GDL82 when visiting Canada? Is UAT merely an ignored broadcast in Canada, or does it need suppressed by shutting the GDL 82 off, or perhaps bypassing it by going mode C transponder directly to the antenna?
 
I was wondering about this. Secton 8 in the install manual doesn't include any performance check with the GDL shut down, so not sure what to expect.
Hello Stan,

Losing power to the GDL 82 during a flight shouldn't cause any damage to the GDL 82 or the transponder as long as the transponder can take a slightly higher VSWR, but you shouldn't operate routinely with the GDL 82 powered off.

There is additional attenuation of the transponder signal when the GDL 82 is left un-powered and connected between the transponder and the antenna, so transponder performance will be affected to some extent.

The insertion loss of operating a powered GDL 82 is quite low (< 1 dB), but it is ~3X higher when not powered.

Thanks,
Steve
 
GPS antenna under the cowl

For those of you that have mounted your GPS antenna under the cowling on a shelf next to other antennas, have you gone back months later and checked the performance and are you still getting acceptable results?
 
Thanks for the reminder

Our GDL-82 antenna is mounted under the cowling but not alongside other antenna. Just checked the PAPR for both flights today and all is well. Installed, tested and promptly forgotten back in February.
Thanks for the reminder!
 
GA35 Antenna Mounting

I am installing a GDL82 with a GA35 antenna in my GTX327 equipped RV6.

I was planning on installing the GPS antenna on top of the foredeck in front of the tip-up canopy.

Has anyone else done that? And did you install the 063" doubler plate under the skin?

Jim Sharkey
RV6
 
I am installing a GDL82 with a GA35 antenna in my GTX327 equipped RV6.

I was planning on installing the GPS antenna on top of the foredeck in front of the tip-up canopy.

Has anyone else done that? And did you install the 063" doubler plate under the skin?

Jim Sharkey
RV6

....I just checked our club's C172 that had the same antenna professionally installed recently with a GTX 345 upgrade. The antenna is mounted on the "roof" behind the windshield, without a doubler - and with some ugly-ly applied sealer around the perimeter and over the mounting screws. It was adjacent to a rib though.

I have made a nut-plate doubler from 032" sheet that covers the screw pattern footprint and will mount the antenna close to one of the fore/aft ribs.
 
I am installing a GDL82 with a GA35 antenna in my GTX327 equipped RV6.

I was planning on installing the GPS antenna on top of the foredeck in front of the tip-up canopy.

Has anyone else done that? And did you install the 063" doubler plate under the skin?

Jim Sharkey
RV6

Jim.

Make your antenna doubler the same thickness as the skin it's to be attached to. Remember that the term "doubler" means you are doubling the skin thickness. Not tripling or quadrupling it. There is sound reason for only doubling and this is a case where more is not necessarily better. You only want to carry the weight and loads of the antenna while restoring the strength and stiffness of the penetrated skin, all the while not creating a hard point or stress concentration where a thin skin carries too much stress at the edge of an overly-thick reinforcing patch.

Jim
 
GTX327 as Power Source for GDL82?

The GTX327 has a Switched Power Output (pin 14).

Note 3 on the wiring schematic for the GTX327 says not to exceed 1.5A at 13.75 VDC input voltage.

The manual for the GDL82 says maximum current draw, with GPS, at 14VDC is 0.5A.

I assume then that I can power the GDL82 from the GTX327 and it will operate when the transponder is switched on?

Jim Sharkey
RV6
 
RV12 GDL82 Option

I wish I had done that.

I saw some plans for adding a GDL82 to the RV12 avionics suite - which I believe was baselined with a GTX327. But I can't find them again.

Do you know if these install plans show the GDL82 powered from the GTX327?

Jim Sharkey
RV6
 
RV12

I saw some plans for adding a GDL82 to the RV12 avionics suite - which I believe was baselined with a GTX327. But I can't find them again.

Do you know if these install plans show the GDL82 powered from the GTX327?

Jim Sharkey
RV6


....found it - WH-00142. Interestingly they splice into the GTX327 power and ground wires - and they don't wire up the fault light or the anonymous switch on the GDL82.
 
....found it - WH-00142. Interestingly they splice into the GTX327 power and ground wires - and they don't wire up the fault light or the anonymous switch on the GDL82.

That is probably because the STC instructions for the GDL-82 explicitly state that this UAT unit is to be connected to the same circuit breaker as the transponder with it's own independent ring terminal stacked on top of the transponder ring terminal. This means you aren't even supposed to have a separate breaker for the GDL-82. So legally powering the GDL-82 from the switched output of the GTX 327 is not allowed per the approved instructions. This would definitely apply to a type certified installation but I don't know if it would to an EAB. I like the idea and wish the approved instructions would allow powering from the switched output of the transponder.

There is no reason not to install an anonymous switch while doing the rest of the work. It's a piece of cake and adds functionality.

Jim
 
That is probably because the STC instructions for the GDL-82 explicitly state that this UAT unit is to be connected to the same circuit breaker as the transponder with it's own independent ring terminal stacked on top of the transponder ring terminal. This means you aren't even supposed to have a separate breaker for the GDL-82. So legally powering the GDL-82 from the switched output of the GTX 327 is not allowed per the approved instructions. This would definitely apply to a type certified installation but I don't know if it would to an EAB. I like the idea and wish the approved instructions would allow powering from the switched output of the transponder.

There is no reason not to install an anonymous switch while doing the rest of the work. It's a piece of cake and adds functionality.

Jim

I wonder if the STC assumes that a ring terminal to the breaker is always an option and is easier that taking the GTX327 connector apart to install a pin at #14. In my case the harness was made with this pin "populated" and the wire coiled and tidied.
 
Would the original intent for the pin 14 switched power be to run the altitude encoder ?? If so, this pin wouldn't be available for the GDL82 ??

I'm getting ready to put a GDL82 in my Decathlon (equipped with a GTX327) so am trying to figure this out. I'll also be putting a GTX327 / GDL82 in my Rocket which should fly in 2020 for the sole reason of the anonymous mode. Garmin says none of their other xponders will have anonymous capability.
 
On yoir Decathlon you don't have a choice. Since it is a type certified aircraft the STC instructions must be followed to the letter. So that means you will hook your GDL 82 power wire to the same breaker as the transponder. Per the approved STC installation instructions.

Jim
 
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GDL82 GPS antenna

I have a RV7 slider - would the GDL82 GPS antenna work if it is mounted between the seats there at shoulder levelL
Skipper RV7
 
I have a RV7 slider - would the GDL82 GPS antenna work if it is mounted between the seats there at shoulder levelL
Skipper RV7

I would think so, my GDL-82 GPS antenna is on the dash in my-7 slider and works fine. You have to have at least 6 ft of coax between the GDL-82 and the puck for impedance purposes so your location would be fine for that.
Figs
 
Antenna blockage?

If I remember correctly, the set up program offers a page with satellite signal strength. You can certainly see what kind of signal strength you get with no people in the cockpit, then add you and a large passenger and see if the signal is impacted. Maybe point the airplane North, and pay particular attention to the satellites the body parts are in front of. Google search might also offer some insight on what frequencies us salt water vessels block.😂
 
Yesterday I tried to download the Installation Tool for the GDL82 from the Garmin website. No joy. Is there something going on with their website ..... or maybe I had my tongue held wrong ........ or what ???
I have the GDL82 installed and ready to go; just need to check it for the latest software (2.01 = anonymous on start-up) and configure it with the Installation Tool.
 
Larry.

I can't help too much with the downloads. I didn't have any trouble but I am sure G3X Expert will be glad to assist. I would offer to send you the downloads via email but I understand such things can irritate the Galactic Empire in Olathe. EDIT: I found the link, see next post below.

The GDL 8X installation tool is different than the firmware update data download. So you will need to download both. Then the installation tool can update the GDL firmware with you giving it the directory path to the new firmware file you downloaded.

One precaution. If you are using a seperate WAAS navigator like a GNS 430W or GTN series then update to the new GDL 82 firmware prior to configuring the RS232 location source from the panel navigator. Also, if you aee updating the panel mount software at the same time accomplish this update prior to linking to the 82.

I recently ran into the issue of having a GDL 82 talking fine with a GTN 750 and subsequently updating the GTN from an ancient level software to the latest GTN software. The latest GTN software added data formats to the serial data and rendered to he GDL inoperative without GPS source. At the same time the GDL firmware was updated and apparently it too added a new data format. It was a goat rope trying to figure out what happened with things cooperating initially followed by having both devices "update" so their RS232 channels were out of synch. Until I connected the dots to diwcover the updates scrambled things.

Point being made is to be sure to update the devices you intend to prior to configuring them to play well together.

Changing the subject, I ought to tell you about the time I tried to put a GDL 82 WAAS GPS antenna under a carbon fiber glareshield (Diamind DA40). Unlike fiberglass carbon fiber is not transparent to GPS signals. I may as well have mounted it on the belly of the airplane. Sheesh. ��

Yesterday I tried to download the Installation Tool for the GDL82 from the Garmin website. No joy. Is there something going on with their website ..... or maybe I had my tongue held wrong ........ or what ???
I have the GDL82 installed and ready to go; just need to check it for the latest software (2.01 = anonymous on start-up) and configure it with the Installation Tool.
 
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Yesterday I tried to download the Installation Tool for the GDL82 from the Garmin website. No joy. Is there something going on with their website ..... or maybe I had my tongue held wrong ........ or what ???
I have the GDL82 installed and ready to go; just need to check it for the latest software (2.01 = anonymous on start-up) and configure it with the Installation Tool.

Larry. Here is a link I found:
https://www8.garmin.com/support/collection.jsp?product=010-01560-31
 
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.

There are other coax types that can be used for the GA 35 WAAS antenna lead and still fall within performance specs at shorter lengths. For example, I like to use double shielded RG316 or even RG 174 which are the very thin coax like come on portable GPS antennas. Even RG58 will work for very short runs as the higher loss allows less cable. The reason RG400 is used is to keep loss minimized and so these other higher-loss cables can be used for short runs for equivalent compliance. The key point is to use brand new cable with properly terminated connectors. Use the db loss/ft specifications posted for these other types of coax to find the new shorter length for the loss required for each type. I can understand where Garmin is coming from wanting the best cable but if they then turn around and require more loss than the quality cable allows that defeats the purpose for very short runs. Garmin has to design to a worse case scenario which is an installation in big aircraft with long runs which can lead to the kind of seemingly contradictory requirement for excess cable for small airplanes at shorter run lengths.
 
There are other coax types that can be used for the GA 35 WAAS antenna lead and still fall within performance specs at shorter lengths. For example, I like to use double shielded RG316 or even RG 174 which are the very thin coax like come on portable GPS antennas. Even RG58 will work for very short runs as the higher loss allows less cable. The reason RG400 is used is to keep loss minimized and so these other higher-loss cables can be used for short runs for equivalent compliance. The key point is to use brand new cable with properly terminated connectors. Use the db loss/ft specifications posted for these other types of coax to find the new shorter length for the loss required for each type. I can understand where Garmin is coming from wanting the best cable but if they then turn around and require more loss than the quality cable allows that defeats the purpose for very short runs. Garmin has to design to a worse case scenario which is an installation in big aircraft with long runs which can lead to the kind of seemingly contradictory requirement for excess cable for small airplanes at shorter run lengths.

Yeah the instructions say "as close as possible" which is a little vague. But I called Garmin and they said that the ~3foot length I have in mind using RG-400 is fine.
 
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GPS antenna location

Has anyone installed the GDL-82 GPS antenna under the bubble canopy?

Does it seem to work?

I have an RV-8 and I'm looking for the best spot. Behind the cockpit doesn't work because the canopy slides back all the way and the canopy crossbar can get in the way. So it's either forward of the windscreen or on the glare shield.

But I'm open to other ideas.
 
The GA 35 works great on the glareshield or aft of the canopy. Most RV-8 folks put it hidden under the cowl as do the other RV models. Usually on a fabricared sheet metal shelf on the firewall. If you insist on exterior mounting I have also seen them under the aft canopy where they are low profile enough to clear the cross-brace when it pops up from the forward position.

Here's a quick photo of under the cowling placement of a GPS antenna. This is not the conventional firewall shelf but rather on the engine mount. You will see a small aluminum plate under it. I am more used to seeing them on a firewall shelf but can't find a photo of that quickly:

Ts32hz9.jpg
 
If it's mounted near the center canopy rail, as shown in the pic above, the curvature is not enough to be a problem. If it was mounted lower down on the turtledeck, where the curvature is more pronounced, it might be an issue.

Roger, thanks.
 
This is the shelf mount on the firewall. The shelf I used is an RV-12 part (P/N F-01201R-1), or you can fabricate one.

IMG_2025-L.jpg


IMG_1972-L.jpg


IMG_1973-L.jpg


IMG_1978-L.jpg
 
Question regarding Circuit Breaker and the GDL 82

Question: Are you REQUIRED to use the same circuit breaker that your transponder is on?

I have 2 Garmin installation guides for the GDL 82:

GDL 82 for the Mooney M20 series which says:

"This GDL 82 is protected by the existing transponder circuit breaker."


And then I have the "GDL 82 TSO Installation Manual"
which says:

"The GDL 82 CAN BE protected by the existing transponder Circuit breaker"


So I'm assuming that the reason they use the same CB in the Mooney is so that you don't have to install a new CB in the certified airplane panel and doesn't have anything to do with electronic technique.

So I read all this as meaning you CAN use the same CB as the transponder but you don't have to.

Am I misinterpreting?

Thanks
 
The GDL 82 STC installation instructions for certified aircraft state that they must both be connected to the same circuit breaker, with their own individual ring terminals. I think the FAA wants to make sure one is never on without the other. And I think the individual ring terminal mandate is for reliability of some sort. I am aware of some experimental installations who use the switched power output of the transponder to power the GDL 82. Seems to work fine.
 
The GDL 82 STC installation instructions for certified aircraft state that they must both be connected to the same circuit breaker, with their own individual ring terminals. I think the FAA wants to make sure one is never on without the other. And I think the individual ring terminal mandate is for reliability of some sort. I am aware of some experimental installations who use the switched power output of the transponder to power the GDL 82. Seems to work fine.

Ok so let's suppose I want to connect both to the same breaker.
I have a GTX 327 Transponder

I am an electronics neophyte so I need some assistance:

The circuit diagram for the GTX 327 shows a 3 amp breaker.

The documentation does not specify a current draw but says that the max power is 22 watts. So I calculated the max current this way:

GTX 327 amps = watts/volts = 22.0/14 = 1.57 amps

The documentation for the GDL 82 says it draws 0.45 amps at 14 volts.

To total current draw of the two devices is:

1.57 + 0.45 = 2.02 amps

So one would think I could use a 3 amp breaker for the combined units.

BUT........

AC43.13 Table 11.3 shows that for 22AWG wire I need a 5 amp breaker.


The GDL 82 circuit diagram says I need a 5 amp breaker
(power line is 22awg I believe)

The GTX 327 circuit diagram says I need only a 3 amp breaker.

So I'm thinking I need to use a 5 amp breaker for the combined units. It's way over the 120% max current draw requirements in the documentation. I'm concerned that a problem would draw much more current than necessary before the breaker trips

Is the 5 amp breaker the correct breaker size to use for the combined units?

Thanks
 
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Circuit breaker protects the wire. Wire is selected to handle the draw. Using a lower circuit breaker then called for by the standard is ok. Since they should be connected in parallel (separate ring terminal for each off of the breaker) each wire is selected for each draw. Circuit breaker should be selected for protecting the smallest gage wire in the circuit. I would select a 3amp breaker as there is no need to have more higher then the total draw, which is what I have for my GDL 82 and SL70.

FYI. AC43.13 Table 11.3 does not show what you need, it shows the maximum for 22AWG wire should be 5 amp breaker. Always want breaker to trip before wire catches on fire.
 
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3 amp will probably work but I always yield to the manufacturer's recommendation. Can't go wrong there. In the GDL 82 manual it says to use a 5 Amp breaker and in my upgrade installs I always change the original GTX 327 breaker from a 3 amp to a 5 amp and use 22 AWG power/ground wires for the GDL and 20AWG power/ground wires for the GTX in accordance with Garmin's installation manuals. The 5 amp is still appropriate for 22AWG for the distances available for wire runs in an RV. Here again I assume you are putting this in an EAB aircraft so you can do whatever you like, such as the aforementioned switched power output circuit from the transponder's D-Sub connector.
 
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The GDL 82 STC installation instructions for certified aircraft state that they must both be connected to the same circuit breaker, with their own individual ring terminals. I think the FAA wants to make sure one is never on without the other. And I think the individual ring terminal mandate is for reliability of some sort. I am aware of some experimental installations who use the switched power output of the transponder to power the GDL 82. Seems to work fine.

So there is no electronic "damage" reason to have one on and one off...it's an FAA thing where they want to be sure both are on?

Thanks
 
So there is no electronic "damage" reason to have one on and one off...it's an FAA thing where they want to be sure both are on?

Thanks

I have no idea. But I don't know if a GTX can transmit through a GDL 82 if it is off.

Jim
 
The GPS antenna I have (package deal from spruce) says that you MUST use the screws provided and that they MUST be torqued to (IIRC) 13-16 pounds.

I believe the GPS antenna is the Garmin GA 35 WAAS GPS antenna

I got screws with the Package and flat washers but no lock washers.

I'm wondering if I should add locks to it....a little uncomfortable without lock washers.
 
The GPS antenna I have (package deal from spruce) says that you MUST use the screws provided and that they MUST be torqued to (IIRC) 13-16 pounds.

I believe the GPS antenna is the Garmin GA 35 WAAS GPS antenna

I got screws with the Package and flat washers but no lock washers.

I'm wondering if I should add locks to it....a little uncomfortable without lock washers.

I bought a pack of stainless flat washers and lock nuts from Ho Depot / Lowes. Good to go.
 
I'm wondering if I should add locks to it....a little uncomfortable without lock washers.

If you feel comfortable with a lock washer put it on. 99.999% chance it will make no difference as the screws are outside the antenna receive field of view. If it does, remove lock washer.
 
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