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  #11  
Old 05-10-2018, 11:32 AM
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Auburntsts Auburntsts is offline
 
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Originally Posted by snopercod View Post
Tell it to Garmin. The installation instructions for the GDL-82 require a large one under the GA 32 WAAS antenna. It's a matter of signal-to-noise ratio, I think. The bigger the ground plane, the more signal. You handheld devices can get away with lesser signal. From this graph, it looks like you get 5dB of gain with a 70x70 cm ground plane, and 0 dB with a 30x30 cm ground plane. If my math is right, you get 3 times the signal with a large ground plane.

And yet neither the GTN nor G3X install manuals mandate a ground plane for the GPS antenna. Go figure...
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  #12  
Old 05-10-2018, 11:45 AM
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Originally Posted by Auburntsts View Post
And yet neither the GTN nor G3X install manuals mandate a ground plane for the GPS antenna. Go figure...
The ground plane requirement for the GDL-82 may have been something the FAA imposed upon Garmin. That's all I can figure...
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  #13  
Old 05-10-2018, 01:00 PM
sritchie sritchie is offline
 
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Originally Posted by RandyAB View Post
Is your overhead console carbon fibre like those provided by Aerosport? If so, my understanding is that you can use it as the ground plane. I was discussing this with a fellow RV10 builder who is an electrical engineer and he said that although GPS antennas don't really require a ground plane, he mounted his under the canopy on overhead console which being carbon fibre, was conductive.
Yes, it's the aerosport console. Okay, that makes sense. I'll go ahead and mount them on the supplied metal inserts... that way I can get my ground plane and ease of installation.
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  #14  
Old 05-10-2018, 02:08 PM
RandyAB RandyAB is offline
 
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Originally Posted by sritchie View Post
Yes, it's the aerosport console. Okay, that makes sense. I'll go ahead and mount them on the supplied metal inserts... that way I can get my ground plane and ease of installation.
FWIW, he says that the GPS has worked flawlessly with that setup. Good luck!
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  #15  
Old 05-12-2018, 10:06 AM
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az_gila az_gila is offline
 
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Originally Posted by sritchie View Post
I'm definitely planning on mounting it INSIDE the cabin, hidden by the overhead console. I agree that velcro on the outside wouldn't be ideal

....
I think that an internal mount for the Garmin GTN650 antenna would violate the manufacturers instructions and its associated STC.

If it's going to be used for IFR operations isn't "approved" (aka STC'd) equipment required?
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  #16  
Old 05-12-2018, 10:43 AM
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Auburntsts Auburntsts is offline
 
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Originally Posted by az_gila View Post
I think that an internal mount for the Garmin GTN650 antenna would violate the manufacturers instructions and its associated STC.

If it's going to be used for IFR operations isn't "approved" (aka STC'd) equipment required?
Just a nit—it’s TSO’d not STC’d.
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  #17  
Old 05-12-2018, 10:45 AM
BobTurner BobTurner is online now
 
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Quote:
Originally Posted by az_gila View Post
I think that an internal mount for the Garmin GTN650 antenna would violate the manufacturers instructions and its associated STC.

If it's going to be used for IFR operations isn't "approved" (aka STC'd) equipment required?
I don’t think you can get an STC for an EAB, since it doesn’t have a type certificate to begin with. I think the acronym you meant was ‘TSO’, and, yes, the TSO specifies external mounting. I take statements ‘it has worked perfectly for me’ with a grain of salt - the TSO requirements have a lot of worse-case scenarios to meet.
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  #18  
Old 05-12-2018, 11:12 AM
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Originally Posted by Auburntsts View Post
Just a nit—it’s TSO’d not STC’d.
Thanks, both of you... you are correct, not enough caffeine this morning...

And as Bob T quotes "it works for me in my plane" doesn't mean that it will pass all of the required tests for full IFR certification.
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Last edited by az_gila : 05-12-2018 at 11:16 AM.
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  #19  
Old 06-17-2018, 06:34 PM
Traash Traash is offline
 
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GTN's need a Gamma 3 capable antenna to allow LPV approaches.
G5 and GDU's need GPS for attitude stabilization and VFR navigation (Gamma1)
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  #20  
Old 06-18-2018, 02:10 PM
DRMA DRMA is offline
 
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One thing to be aware of. When I talked to Van's technical support they said they do NOT recommend drilling any holes in the fiberglass cabin top that are not specified in the plans, as the fiberglass top is a structural member. So if you can mount the antenna below the cabin top, say inside the overhead console, without drilling any holes through the top, you should be ok. After a lot of reading and study, I came up with antenna arrangements that allow me to mount both GPS antennas, one Com antenna, and the ELT antenna all on the aluminum top skin behind the fiberglass cabin top, while still maintaining recommended spacing between antennas, ground planes, and distance from the vertical stab.

The second Com antenna is on the rear fuselage bottom, with the Xponder/ADS-B antenna forward in the tunnel but away from the gear legs.

Regards
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