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GPS antenna mounting

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Ed Godfrey

Joined: 05 May 2009
Posts: 47

Posted: Sun Aug 06, 2017 8:42 am Post subject: GPS antenna mounting

I would like to ask, of those who mounted your GPS antenna on the 

cabin top, are you getting the performance from it that you expected? 

Did you install a ground plane? Also, what screws did you use to mount 

it. I have been looking for some MS24693-C286 screws and am not coming 

up with anything. Thanks.



Ed Godfrey

philperry9

Joined: 23 Nov 2011
Posts: 381

Posted: Sun Aug 06, 2017 9:32 am Post subject: GPS antenna mounting

I have been very happy with my performance so far.    The only thing I wish I had considered was installing them under the glass cabin top and inside my overhead air console.  It would have been nice to not ouch a hole in the top of the plane and also protect the antenna from the WX and UV; hopefully extending the life of the antenna and rescuing another leak point to seal up. 



But the top has served me well to this point.    Others might be able to comment on the performance inside the overhead air (if you have it).  Just something to consider. 



Phil



Sent from my iPhone



 	  Quote: 	
		   On Aug 6, 2017, at 11:42 AM, Ed Godfrey <egodfrey(at)ameritech.net> wrote:

 

 

 

    I would like to ask, of those who mounted your GPS antenna on the cabin top, are you getting the performance from it that you expected? Did you install a ground plane? Also, what screws did you use to mount it. I have been looking for some MS24693-C286 screws and am not coming up with anything. Thanks.

 

 Ed Godfrey

Kellym

Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ

Posted: Sun Aug 06, 2017 1:50 pm Post subject: GPS antenna mounting

I look at GPS antenna location based on the purpose and approval basis 

of the antenna. For my GTN650 to meet IFR performance standards, I 

mounted on cabin top with the recommended ground plane (partly sheet 

metal, partly aluminum foil) per Garmin instructions. For the GPS that 

drives my EFIS display, I mounted it in front of the firewall, perhaps 

10", underneath the cowling.  If mounting GPS antenna to drive ADS-B 

out, I would try to follow manufacturer's recommendations.

The Garmin needs a better view of the sky and takes longer to lock on 

than my Dynon, but it has more required validation to perform.



On 8/6/2017 9:42 AM, Ed Godfrey wrote:

 	  Quote: 	
		   

 

      I would like to ask, of those who mounted your GPS antenna on the 

 cabin top, are you getting the performance from it that you expected? 

 Did you install a ground plane? Also, what screws did you use to mount 

 it. I have been looking for some MS24693-C286 screws and am not coming 

 up with anything. Thanks.

 

 Ed Godfrey

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

Bob Turner

Joined: 03 Jan 2009
Posts: 885
Location: Castro Valley, CA

Posted: Sun Aug 06, 2017 3:43 pm Post subject: Re: GPS antenna mounting

I mounted mine on top of the skin, a foot behind the baggage bulkhead:

1. This area has metal skin so the ground plane is there. I did use a doubler.

2. My 420W required a certain MINIMUM coax run, so there was no "extra" coax involved in this location. 

3. My guess was that there was slightly less drag in this location (top of the cabin is convex which will speed up the airflow a bit).



Works fine.

_________________
Bob Turner
RV-10 QB

dmaib(at)mac.com
Guest

Posted: Sun Aug 06, 2017 4:10 pm Post subject: GPS antenna mounting

I did exactly the same thing Bob Turner did. Works great. 



David Maib

 	  Quote: 	
		   On Aug 6, 2017, at 7:43 PM, Bob Turner <bobturner(at)alum.rpi.edu> wrote:

 

 

 

 I mounted mine on top of the skin, a foot behind the baggage bulkhead:

 1. This area has metal skin so the ground plane is there. I did use a doubler.

 2. My 420W required a certain MINIMUM coax run, so there was no "extra" coax involved in this location. 

 3. My guess was that there was slightly less drag in this location (top of the cabin is convex which will speed up the airflow a bit).

 

 Works fine.

 

 --------

 Bob Turner

 RV-10 QB

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=471558#471558

Ed Godfrey

Joined: 05 May 2009
Posts: 47

Posted: Sun Aug 06, 2017 5:14 pm Post subject: GPS antenna mounting

Bob and David,

      I was considering putting it back there, but I ran into issues 

with the separation of the GPS antenna, a comm antenna and the ELT antenna.



Ed



On 8/6/2017 7:09 PM, David Maib wrote:

 	  Quote: 	
		   



 I did exactly the same thing Bob Turner did. Works great.



 David Maib

> On Aug 6, 2017, at 7:43 PM, Bob Turner <bobturner(at)alum.rpi.edu> wrote:

>

> 

>

> I mounted mine on top of the skin, a foot behind the baggage bulkhead:

> 1. This area has metal skin so the ground plane is there. I did use a doubler.

> 2. My 420W required a certain MINIMUM coax run, so there was no "extra" coax involved in this location.

> 3. My guess was that there was slightly less drag in this location (top of the cabin is convex which will speed up the airflow a bit).

>

> Works fine.

>

> --------

> Bob Turner

> RV-10 QB

>

>

> Read this topic online here:

>

> http://forums.matronics.com/viewtopic.php?p=471558#471558

>

cooprv7(at)yahoo.com
Guest

Posted: Sun Aug 06, 2017 7:44 pm Post subject: GPS antenna mounting

X3, works great mounted just aft of the fiberglass with 845 hours.  



Marcus



 	  Quote: 	
		   On Aug 6, 2017, at 8:09 PM, David Maib <dmaib(at)mac.com> wrote:

 Do not archive

 

 

 I did exactly the same thing Bob Turner did. Works great. 

 

 David Maib

 

 

> On Aug 6, 2017, at 7:43 PM, Bob Turner <bobturner(at)alum.rpi.edu> wrote:

> 

> 

> 

> I mounted mine on top of the skin, a foot behind the baggage bulkhead:

> 1. This area has metal skin so the ground plane is there. I did use a doubler.

> 2. My 420W required a certain MINIMUM coax run, so there was no "extra" coax involved in this location. 

> 3. My guess was that there was slightly less drag in this location (top of the cabin is convex which will speed up the airflow a bit).

> 

> Works fine.

> 

> --------

> Bob Turner

> RV-10 QB

> 

> 

> 

> 

> Read this topic online here:

> 

> http://forums.matronics.com/viewtopic.php?p=471558#471558

> 

> 

> 

> 

> 

> 

> 

> 

>

Bob Turner

Joined: 03 Jan 2009
Posts: 885
Location: Castro Valley, CA

Posted: Sun Aug 06, 2017 8:22 pm Post subject: Re: GPS antenna mounting

My ELT is 4 or 5 feet further aft, and I have no com antennas on top, so separation from com antennas may be a concern.

 	  Ed Godfrey wrote: 	
		  Bob and David,

      I was considering putting it back there, but I ran into issues 

with the separation of the GPS antenna, a comm antenna and the ELT antenna.



Ed



On 8/6/2017 7:09 PM, David Maib wrote:

 	  Quote: 	
		   



 I did exactly the same thing Bob Turner did. Works great.



 David Maib

> On Aug 6, 2017, at 7:43 PM, Bob Turner <bobturner> wrote:

>

> 

>

> I mounted mine on top of the skin, a foot behind the baggage bulkhead:

> 1. This area has metal skin so the ground plane is there. I did use a doubler.

> 2. My 420W required a certain MINIMUM coax run, so there was no "extra" coax involved in this location.

> 3. My guess was that there was slightly less drag in this location (top of the cabin is convex which will speed up the airflow a bit).

>

> Works fine.

>

> --------

> Bob Turner

> RV-10 QB

>

>

> Read this topic online here:

>

> http://forums.matronics.com/viewtopic.php?p=471558#471558

>

_________________
Bob Turner
RV-10 QB

dmaib(at)mac.com
Guest

Posted: Mon Aug 07, 2017 5:32 am Post subject: GPS antenna mounting

My comm antennas are on the belly. My ELT antenna is closer to the GPS antenna than recommended. I've not had any discernible issues at all. 



David Maib

 	  Quote: 	
		   On Aug 7, 2017, at 12:22 AM, Bob Turner <bobturner(at)alum.rpi.edu> wrote:

 

 

 

 My ELT is 4 or 5 feet further aft, and I have no com antennas on top, so separation from com antennas may be a concern.

 

 

 

 Ed Godfrey wrote:

> Bob and David,

>      I was considering putting it back there, but I ran into issues 

> with the separation of the GPS antenna, a comm antenna and the ELT antenna.

> 

> Ed

> 

>> On 8/6/2017 7:09 PM, David Maib wrote:

>> 

>> 

>> 

>> I did exactly the same thing Bob Turner did. Works great.

>> 

>> David Maib

>> 

>> 

>>> On Aug 6, 2017, at 7:43 PM, Bob Turner  wrote:

>>> 

>>> 

>>> 

>>> I mounted mine on top of the skin, a foot behind the baggage bulkhead:

>>> 1. This area has metal skin so the ground plane is there. I did use a doubler.

>>> 2. My 420W required a certain MINIMUM coax run, so there was no "extra" coax involved in this location.

>>> 3. My guess was that there was slightly less drag in this location (top of the cabin is convex which will speed up the airflow a bit).

>>> 

>>> Works fine.

>>> 

>>> --------

>>> Bob Turner

>>> RV-10 QB

>>> 

>>> 

>>> 

>>> 

>>> Read this topic online here:

>>> 

>>> http://forums.matronics.com/viewtopic.php?p=471558#471558

>>> 

>>> 

>>> 

>>> 

>>> 

>>> 

>>> 

>>> 

>>> 

>> 

>> 

>> 

>> 

>> 

>> 

> 

 

 

 --------

 Bob Turner

 RV-10 QB

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=471578#471578

fdombroski

Joined: 14 Mar 2009
Posts: 33
Location: Westfield NJ

Posted: Mon Aug 07, 2017 5:35 am Post subject: Re: GPS antenna mounting

I buried my GTN antenna in the cabin top above the access plate in the overhead console.  Works flawlessly, no cutting of the outside skin necessary.

Cheers,

Frank

_________________
Frank Dombroski
Multiple Offender RV-8, 7A, 10 x 2
RV-10 2.0 N46VT 2015
KSMQ Somerset Airport NJ

Kellym

Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ

Posted: Mon Aug 07, 2017 5:42 am Post subject: GPS antenna mounting

ELT interference complaints are normally with com radios not GPS. 1st 

generation ELTs (designed circa 1973-75) were especially bad about being 

plagued by responding to strong broadcast signals, such as being near 

TV, radio stations, which would actually excite the oscillator in the 

ELT, rebroadcasting just enough signal to break squelch and interfere 

with reception and squelch on VHF com frequencies. My previous plane had 

this when all rod antennas (com, ELT and Loran) were on top of fuselage. 

Once Loran was eliminated and one com was moved to belly, almost all of 

problem went away. I do not know how much improvement has been designed 

into 2nd generation 121.5 or 406 ELTs.

On 8/7/2017 6:31 AM, David Maib wrote:

 	  Quote: 	

 My comm antennas are on the belly. My ELT antenna is closer to the GPS antenna than recommended. I've not had any discernible issues at all.

 David Maib

> On Aug 7, 2017, at 12:22 AM, Bob Turner <bobturner(at)alum.rpi.edu> wrote:

>

> 

>

> My ELT is 4 or 5 feet further aft, and I have no com antennas on top, so separation from com antennas may be a concern.

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

trigo(at)mail.telepac.pt
Guest

Posted: Mon Aug 07, 2017 11:18 am Post subject: GPS antenna mounting

Frank



It sounds a good idea but in that case the antenna cable will be hanging from the ceiling, or better said, from the  access plate. Isn't that so?



Carlos



Enviado do meu iPhone



No dia 07/08/2017, às 14:35, fdombroski <frankdombroski(at)gmail.com> escreveu:



 	  Quote: 	
		   

 

 I buried my GTN antenna in the cabin top above the access plate in the overhead console.  Works flawlessly, no cutting of the outside skin necessary.

 Cheers,

 Frank

 

 --------

 Frank Dombroski

 Multiple Offender RV-8, 7A, 10 x 2

 RV-10 2.0 N46VT  2015

 KSMQ Somerset Airport NJ

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=471587#471587

fdombroski

Joined: 14 Mar 2009
Posts: 33
Location: Westfield NJ

Posted: Tue Aug 08, 2017 4:50 am Post subject: Re: GPS antenna mounting

The antenna is flush with the inside surface, and the TNC is a 90 degree fitting.  there is no clearance issue.  The antenna and filler consume the void tightly, and a ground plate covers the inside skin cut out.  



Antenna cable and wires run up the center post.



Here is a photo prior to the ground/mount plate installation.



Best,

Frank

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_________________
Frank Dombroski
Multiple Offender RV-8, 7A, 10 x 2
RV-10 2.0 N46VT 2015
KSMQ Somerset Airport NJ

Dave Saylor

Joined: 11 Jan 2015
Posts: 209
Location: GILROY, CA

Posted: Tue Aug 08, 2017 5:09 am Post subject: GPS antenna mounting

Frank,



That's a clever use of what seems like wasted volume, but please consider that the thickness of the cabin top provides a structural function.  Are you taking some measures to reinforce the compromised area, like a cover plate that acts as a doubler, or additional plies below the antenna?  Of course we can do what we want, but it sure seems to me like that mod gives up some crash worthiness.

--Dave

On Tue, Aug 8, 2017 at 5:50 AM, fdombroski <frankdombroski(at)gmail.com (frankdombroski(at)gmail.com)> wrote:

 	  Quote: 	
		  --> RV10-List message posted by: "fdombroski" <frankdombroski(at)gmail.com (frankdombroski(at)gmail.com)>

 

 The antenna is flush with the inside surface, and the TNC is a 90 degree fitting.  there is no clearance issue.  The antenna and filler consume the void tightly, and a ground plate covers the inside skin cut out.

 

 Here is a photo prior to the ground/mount plate installation.

 

 Best,

 Frank

 

 --------

 Frank Dombroski

 Multiple Offender RV-8, 7A, 10 x 2

 RV-10 2.0 N46VT  2015

 KSMQ Somerset Airport NJ

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=471613#471613

 

 

 

 

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_________________
--Dave
KWVI

Mauledriver(at)nc.rr.com
Guest

Posted: Wed Aug 09, 2017 8:26 am Post subject: GPS antenna mounting

I mounted the antenna for my G430w on the top - no ground plane was 

specified.  Works perfectly at all times.  It also seals up easily with 

a bit of silicon sealant used as a gasket.  Very unobtrusive.



I chose not to try and get fancy with the WAAS antenna since it is 

critical to IFR operations.  A talk by a local radio shop convinced me 

further on that point.



I have a lot of extra cable for the short run but understand that the 

whole system is tuned and no cable should be removed.  So there is a big 

coil of cable under my hood.



On 8/6/2017 12:42 PM, Ed Godfrey wrote:

 	  Quote: 	
		   



     I would like to ask, of those who mounted your GPS antenna on the 

 cabin top, are you getting the performance from it that you expected? 

 Did you install a ground plane? Also, what screws did you use to mount 

 it. I have been looking for some MS24693-C286 screws and am not coming 

 up with anything. Thanks.



 Ed Godfrey






	




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Bob Turner

Joined: 03 Jan 2009
Posts: 885
Location: Castro Valley, CA

Posted: Wed Aug 09, 2017 4:08 pm Post subject: Re: GPS antenna mounting

Not sure I'd use the word "tuned". The extra coax is there just for its loss, since at these frequencies no coax is perfect.

Seems Garmin bought an OEM antenna and put their name on it, but the antenna has too much gain for the receiver, hence the need for some attenuation or loss in the coax.

_________________
Bob Turner
RV-10 QB

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