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  #21  
Old 09-12-2019, 11:20 PM
rongawer rongawer is offline
 
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Quote:
Originally Posted by Walt View Post
At least one of the G3X screens needs it's own antenna, for dual screens I use one for each.
No, they work just fine with input from either external source and sharing that data, using the GTN. And having the G5 with it's own valid antenna, it can share GPS data with the G3X, much like a GPS 20 will as well. And since the OP stated they have a GTN, no additional antenna is required for the G3X. Lastly, they do have internal GPS as well, but it is not shared.

If you want your G3X to have it's own antenna, you can do that, but they don't need it. I can attest to this in practice. What's more, the GDU's will only use one GPS signal source at a time, so if you have the GTN configured to provide that signal as an external source, then the internal source (which includes attaching a GA 56 directly to the GDU) won't even be used, except as a backup you could select if the GTN failed. But, you have the G5, right? It can provide that GPS signal as well when configured with it's own antenna.

I see a GA56 for the G5 and a GA 35 for the GTN and that's redundancy and all you really need for GPS related antennas.
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Ron Gawer

- RV10, Build in progress.
- RV12, N975G, "The Commuter"...many great hours and happy landings so far.
- Several others that are now just great memories for me.

Last edited by rongawer : 09-12-2019 at 11:29 PM.
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  #22  
Old 09-13-2019, 06:21 AM
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Walt Walt is offline
 
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Quote:
Originally Posted by rongawer View Post
No, they work just fine with input from either external source and sharing that data, using the GTN. And having the G5 with it's own valid antenna, it can share GPS data with the G3X, much like a GPS 20 will as well. And since the OP stated they have a GTN, no additional antenna is required for the G3X. Lastly, they do have internal GPS as well, but it is not shared.

If you want your G3X to have it's own antenna, you can do that, but they don't need it. I can attest to this in practice. What's more, the GDU's will only use one GPS signal source at a time, so if you have the GTN configured to provide that signal as an external source, then the internal source (which includes attaching a GA 56 directly to the GDU) won't even be used, except as a backup you could select if the GTN failed. But, you have the G5, right? It can provide that GPS signal as well when configured with it's own antenna.

I see a GA56 for the G5 and a GA 35 for the GTN and that's redundancy and all you really need for GPS related antennas.
Maybe the G3Xpert will jump in here, the below is from their manual which I tend to believe:

7 GDU 45X (DISPLAY UNIT) INSTALLATION

NOTE
"GPS data is used for ADAHRS sensor drift correction, so at least one source of GPS data is required. This requirement can be met by installing a GPS 20A, or by connecting a GPS antenna to at least one GDU GPS receiver. In a system with multiple GDU displays, additional GPS antennas may be connected to the other displays for redundancy, if desired."
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EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
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Last edited by Walt : 09-13-2019 at 06:32 AM.
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  #23  
Old 09-13-2019, 08:50 AM
rongawer rongawer is offline
 
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Quote:
Originally Posted by Walt View Post
Maybe the G3Xpert will jump in here, the below is from their manual which I tend to believe:

7 GDU 45X (DISPLAY UNIT) INSTALLATION

NOTE
"GPS data is used for ADAHRS sensor drift correction, so at least one source of GPS data is required. This requirement can be met by installing a GPS 20A, or by connecting a GPS antenna to at least one GDU GPS receiver. In a system with multiple GDU displays, additional GPS antennas may be connected to the other displays for redundancy, if desired."
Exactly; if you don't have an external GPS source, then you need to connect an antenna directly to one of GDU's, but the OP has an external navigation source, along with a G5 to provide a redundant ADAHRS and GPS source. The paragraph below is from the G5 installation manual for non-certified aircraft:

"1.2 G5 Overview
The G5 is an electronic instrument display capable of operating as a standalone flight display or a fully integrated backup instrument for G3X systems. It features a bright, sunlight readable, 3.5-inch color display which is sized to fit in a standard 3-1/8-inch instrument cutout. With integrated attitude/ air data sensors and GPS, the G5 replaces traditional electromechanical standby instruments by combining essential information into one easy-to-read display. The G5 seamlessly integrates with other G5 units in the same aircraft and with G3X systems via the CAN network. When installed as part of a G3X system, the G5 provides a redundant source of attitude and air data to the G3X displays, and additionally provides backup autopilot control allowing coupled GPS approaches to be flown or continued in the event that the primary flight display is unavailable. When installed as a standalone system, the G5 can also perform the autopilot function. In the case of aircraft power loss, the optional battery backup sustains the G5 flight display with up to 4 hours of emergency power."

Walt, the GDU's only use the the individually attached GPS antenna for ADAHRS data while using navigation data from an external source, such as a GTN. But this data is also being provided on CAN bus from the G5, so the additional antenna connected to the GDU is simply more redundancy. I'm not saying don't do it - for that matter you can attach an antenna to both PFD, MFD and even a third GDU, if desired - I'm simply saying it's not needed and the OP's question is "What antennas do I need?"

I have done this setup and it works well.
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Ron Gawer

- RV10, Build in progress.
- RV12, N975G, "The Commuter"...many great hours and happy landings so far.
- Several others that are now just great memories for me.

Last edited by rongawer : 09-13-2019 at 08:59 AM.
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  #24  
Old 09-13-2019, 09:55 AM
rongawer rongawer is offline
 
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Quote:
Originally Posted by rocketman1988 View Post
"...Four GPS units Bob?..."

The GA35 is for the GTN650

The GA57X is for the GDL51R XM/GPS

The GA26C's are for the GDUs. These will go on the glare shield.

I will have to ask Stein about the GA26C for the G5...
I'm not Stein, nor G3Xpert, so my advice is probably only worth what you're paying for it.... however, I can confirm the G5 will use a GA26C antenna. Below is an excerpt from the G5 installation manual:

Table 4-2 Supported Garmin Antennas
Model
Part Number
Install Manual
Mounting Configuration
GA 26C (GPS)
011-00149-04
190-00082-00
Flange, Magnetic, or Suction Cup Mounts (in-cabin)
GA 35 (GPS/WAAS)
013-00235-0X
190-00848-00
Thru-Mount (tear drop form factor)
GA 36 (GPS/WAAS)
013-00244-0X
190-00848-00
Thru-Mount (ARINC 743 form factor)
GA 56 (GPS)
011-00134-00
190-00094-00
Stud Mount (tear drop form factor)
GA 57X (GPS/XM)
011-01032-10
190-00522-02
Thru-Mount (ARINC 743 form factor)
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Ron Gawer

- RV10, Build in progress.
- RV12, N975G, "The Commuter"...many great hours and happy landings so far.
- Several others that are now just great memories for me.
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  #25  
Old 09-13-2019, 10:57 AM
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g3xpert g3xpert is offline
 
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Quote:
Originally Posted by RandyAB View Post
Building an IFR machine and am planning dual G3X, G5, and GTN750. Aside from the WAAS antenna which I believe is the GA35, what other GPS antennae would be recommended?
Hello Randy,

We recommend you install a GPS for antenna for the GDU 4XX PFD (e.g. GA 26C or GA 56), the G5 (e.g. GA 26C or GA 56), and the GTN 750 (e.g. GA 35/36).

As explained in the G3X installation manual, at least one of the GDU 4XX displays must have an antenna connected unless you have a GPS 20A, but even in that case, we still recommend an antenna on the PFD display for backup to the GPS 20A.

I like to tell customers that the most important GPS in the aircraft is not the GTN, but rather the high performance WAAS GPS receiver built into each GDU 4XX display because it provides GPS acceleration data used by the GSU 25 ADAHRS to correct for small drifting errors in the solid state attitude sensors.

The GSU 25 ADAHRS can use air data and magnetometer data to correct for sensor drift in the absence of GPS data, but the highest level of performance and accuracy is only obtained when GPS data is available and used for aiding.

The GPS data from the GTN and G5 can be used as backup navigation data for the GDU displays, but it cannot currently be used to aid the GSU 25 ADAHRS.

Interestingly, there are 2 additional sources of GPS data (besides the GDU and GPS 20A) which provide data that can be used to aid the GSU 25, and that is a GTX 345 w/GPS and a GNX 375. Just like when using a GPS 20A, we still recommend that at least the PFD have its own antenna.

Note also that the G5 backup instrument can use either its internal GPS receiver or the MapMX data it is receiving directly from the GTN for attitude sensor aiding, but in some kind of aircraft power emergency, where you might be left with only the G5 operating on its internal backup battery, you will be glad that you connected an antenna to the G5. Like the GSU 25, the G5 can use alternate sources of aiding, but GPS aiding provides the highest accuracy.

Let us know if you have additional questions.

Thanks,
Steve
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Last edited by g3xpert : 09-13-2019 at 05:25 PM. Reason: spelling
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  #26  
Old 09-13-2019, 01:33 PM
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Walt Walt is offline
 
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Quote:
Originally Posted by rongawer View Post
Walt, the GDU's only use the the individually attached GPS antenna for ADAHRS data while using navigation data from an external source, such as a GTN. But this data is also being provided on CAN bus from the G5, so the additional antenna connected to the GDU is simply more redundancy. I'm not saying don't do it - for that matter you can attach an antenna to both PFD, MFD and even a third GDU, if desired - I'm simply saying it's not needed and the OP's question is "What antennas do I need?"

I have done this setup and it works well.
Quote:
Originally Posted by g3xpert View Post
Hello Randy,

As explained in the G3X installation manual, at least one of the GDU 4XX displays must have an antenna connected unless you have a GPS 20A, but even in that case, we still recommend an antenna on the PFD display for backup to the GPS 20A.

I like to tell customers that the most important GPS in the aircraft is not the GTN, but rather the high performance WAAS GPS receiver built into each GDU 4XX display because it provides GPS acceleration data used by the GSU 25 ADAHRS to correct for small drifting errors in the solid state attitude sensors.

The GSU 25 ADAHRS can use air data and magnetometer data to correct for sensor drift in the absence of GPS data, but the highest level of performance and accuracy is only obtained when GPS data is available and used for aiding.

The GPS data from the GTN and G5 can be used as backup navigation data for the GDU displays, but it cannot currently be used to aid the GSU 25 ADAHRS.

Thanks,
Steve
Thanks for jumping in here Steve!

Ron, perhaps the above will change your mind? Steve is the brains behind the G3X and I take his word as gospel. I guess we could argue the semantics of "required" vs "recommended" but when the manufacturer "recommends" something they generally have a good reason for it.
__________________
Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
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  #27  
Old 09-13-2019, 03:10 PM
rongawer rongawer is offline
 
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Quote:
Originally Posted by Walt View Post
Thanks for jumping in here Steve!

Ron, perhaps the above will change your mind? Steve is the brains behind the G3X and I take his word as gospel. I guess we could argue the semantics of "required" vs "recommended" but when the manufacturer "recommends" something they generally have a good reason for it.
Walt, I don't see any contrary information here or anything to be changed from what has been said, although it's nice to hear that the GNX 375 can provide that data to the GSU 25, as that's what I'm planning for my RV10. Again, it's all about redundancy and want vs need. I can tell you that the system works well using the ADAHRS data from the G5; it's going to be hard to argue against my own experience. My point is defining minimum, or functional, versus redundancies.

Fortunately, Garmin has a very well integrated environment that allows you to expand to just about any level of redundancy you desire, but the minimum required is just that. Adding a GPS antenna to one or both of the GDU's and then adding a G5 does give you multiple redundant ADAHRS capability - and that's something I would do before adding a second GSU 25 - but you could do that too if even more redundancy is your goal.

Going hard IFR? Add more. Day VFR? The minimum will be just fine...I think it's important to understand the difference.
__________________
Ron Gawer

- RV10, Build in progress.
- RV12, N975G, "The Commuter"...many great hours and happy landings so far.
- Several others that are now just great memories for me.

Last edited by rongawer : 09-13-2019 at 04:32 PM. Reason: grammar
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  #28  
Old 09-13-2019, 05:36 PM
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Walt Walt is offline
 
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Ron, The only reason I continue this silly "debate" is I think it's important that folks follow the manufacturers recommendations to achieve the level of performance designed into the system, and I wish you would stop saying that it ok to not install the recommended GPS antennas/sources because it works for you.

I think you are somehow reading into Steve's comments what you want to hear.
It's not about redundancy.

Please read Steve's comment below again:

"I like to tell customers that the most important GPS in the aircraft is not the GTN, but rather the high performance WAAS GPS receiver built into each GDU 4XX display because it provides GPS acceleration data used by the GSU 25 ADAHRS to correct for small drifting errors in the solid state attitude sensors.

The GSU 25 ADAHRS can use air data and magnetometer data to correct for sensor drift in the absence of GPS data, but the highest level of performance and accuracy is only obtained when GPS data is available and used for aiding."

Steve has already included the GPS sources that will support the GSU25 ADAHRS aiding so no need to repeat that info again.
__________________
Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154

Last edited by Walt : 09-13-2019 at 06:17 PM.
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  #29  
Old 09-13-2019, 06:40 PM
rongawer rongawer is offline
 
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Quote:
Originally Posted by Walt View Post
Ron, The only reason I continue this silly "debate" is I think it's important that folks follow the manufacturers recommendations to achieve the level of performance designed into the system, and I wish you would stop saying that it ok to not install the recommended GPS antennas/sources because it works for you.

I think you are just reading into Steve's comments what you want to hear.
Watch my lips: It's not about redundancy.

Please read Steve's comment below again:

"I like to tell customers that the most important GPS in the aircraft is not the GTN, but rather the high performance WAAS GPS receiver built into each GDU 4XX display because it provides GPS acceleration data used by the GSU 25 ADAHRS to correct for small drifting errors in the solid state attitude sensors.

The GSU 25 ADAHRS can use air data and magnetometer data to correct for sensor drift in the absence of GPS data, but the highest level of performance and accuracy is only obtained when GPS data is available and used for aiding."

Steve has already included the GPS sources that will support the GSU25 ADAHRS aiding so no need to repeat that info again.
Ok, Walt, I'll continue, although I don't actually consider it a debate... first, re-read my previous posts; I haven't told anyone not to use an antenna or not perform an installation; in fact, everything I've said came from Garmin instructions, so I'm not avoiding those either - you may use all of the antennas you want; I'm simply pointing out options.

You may have missed my point that you can get ADAHRS data on the G3X from the G5. You don't even need to have a GSU 25 for this to occur. And seeing you highlighted "It's not about redundancy", not including additional antennas or the GSU 25 saves cost and effort. For that matter, you don't even need the GDU's if you have the G5, saving even more money and installation effort.

Now, does it make sense to install a GPS antenna if you're installing a PFD? Maybe. How about on the MFD too? Maybe as well. It makes sense to come in out of the rain when it's thundering out, but there are folks that don't. It's their choice, and level of risk they perceive as ok.

Steve pointed out, there are other options for GPS sources to the GDU, so you really don't need to have the extra antenna - unless redundancy is actually a concern for you.

Do you want an antenna on all your GDU's? Maybe. The OP could have 4 GPS antennas for their installation described if they wanted them, but they only need two to make the "system" work - and that was the actual question.
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- RV10, Build in progress.
- RV12, N975G, "The Commuter"...many great hours and happy landings so far.
- Several others that are now just great memories for me.
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  #30  
Old 09-13-2019, 06:45 PM
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Mark33 Mark33 is offline
 
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Default GDL-82 VS. GPS 20A

Quote:
Originally Posted by g3xpert View Post

We recommend you install a GPS for antenna for......the G5 (e.g. GA 26C or GA 56).....

As explained in the G3X installation manual, at least one of the GDU 4XX displays must have an antenna connected unless you have a GPS 20A, but even in that case, we still recommend an antenna on the PFD display for backup to the GPS 20A........

Note also that the G5 backup instrument can use either its internal GPS receiver or the MapMX data it is receiving directly from the GTN for attitude sensor aiding, but in some kind of aircraft power emergency, where you might be left with only the G5 operating on its internal backup battery, you will be glad that you connected an antenna to the G5. Like the GSU 25, the G5 can use alternate sources of aiding, but GPS aiding provides the highest accuracy.....

Thanks,
Steve
Steve,

You mentioned the the GPS 20A as playing an important part in redundancy. Will the WAAS antenna that’s part of the GDL-82 play the same redundancy roll when being installed along with a stand-alone G-5/660 combo?
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