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gps antenna under glassfibre?

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rowlandcarson(at)gmail.co
Guest

Posted: Sat Nov 07, 2020 5:54 am Post subject: gps antenna under glassfibre?

In my Europa build, until now I’ve been planning to provide my Trig TT21 transponder with a GPS position signal from my Garrecht TRX-2000 traffic monitor which has a built-in GPS receiver.



However, with the CAA offering rebates on conspicuity equipment purchases, I am considering a Trig TN72 with a TA50 antenna. This would allow the TT21 to show a SIL of 1 (rather than 0 with the TRX-2000) and thus be more visible to other traffic.



However, with a lot of my installation already done (or at least frozen) I am not sure where I can put the TA50 antenna. On top of the instrument module I have 3 GPS antennas already (for Garmin GPSmap 295, TRX-2000 & Dynon D2 - see http://www.rowlandcarson.org.uk/aviation/europa_435/im_gps_antennae.php). I have separated those antennae by the 6 inches that I found as a recommendation on a Garmin marine website.



I am wondering if it would be OK to put the TA50 inside the roof where I have plenty of space, and whether that would reduce the GPS signal too much. The Europa fuselage is made from inner and outer layers (apparently mostly double) of pre-preg with a thin layer of brown foam between.



Any advice appreciated, or suggestions for a better place to ask this question.



in friendship



Rowland



| Rowland Carson          ... that's Rowland with a 'w' ...

| <rowlandcarson(at)gmail.com>            http://www.rowlandcarson.org.uk

| Skype, Twitter: rowland_carson      Facebook: Rowland Carson

user9253

Joined: 28 Mar 2008
Posts: 1925
Location: Riley TWP Michigan

Posted: Sat Nov 07, 2020 6:35 am Post subject: Re: gps antenna under glassfibre?

Either the instrument panel or the roof should work OK.

I would put the new antenna on the instrument panel panel to make installation easier.

6 inches apart is perfect, but 4 inches apart is good enough.

Jim Weir recommends RG-174 cable.

_________________
Joe Gores

Ceengland

Joined: 11 Oct 2020
Posts: 391
Location: MS

Posted: Sat Nov 07, 2020 8:16 am Post subject: gps antenna under glassfibre?

On 11/7/2020 7:48 AM, Rowland Carson wrote:

 	  Quote: 	
		   



 In my Europa build, until now I’ve been planning to provide my Trig TT21 transponder with a GPS position signal from my Garrecht TRX-2000 traffic monitor which has a built-in GPS receiver.



 However, with the CAA offering rebates on conspicuity equipment purchases, I am considering a Trig TN72 with a TA50 antenna. This would allow the TT21 to show a SIL of 1 (rather than 0 with the TRX-2000) and thus be more visible to other traffic.



 However, with a lot of my installation already done (or at least frozen) I am not sure where I can put the TA50 antenna. On top of the instrument module I have 3 GPS antennas already (for Garmin GPSmap 295, TRX-2000 & Dynon D2 - see http://www.rowlandcarson.org.uk/aviation/europa_435/im_gps_antennae.php). I have separated those antennae by the 6 inches that I found as a recommendation on a Garmin marine website.



 I am wondering if it would be OK to put the TA50 inside the roof where I have plenty of space, and whether that would reduce the GPS signal too much. The Europa fuselage is made from inner and outer layers (apparently mostly double) of pre-preg with a thin layer of brown foam between.



 Any advice appreciated, or suggestions for a better place to ask this question.



 in friendship



 Rowland

As a data point, many RV-x builders mount a small metal shelf on the hot 
	


side of the firewall, just under the 'glass cowl. As long as there isn't 

a lot of carbon in the structure, or a lot of metal in the paint, it 

should work fine inside the structure. Can you push the fuselage 

outdoors and do a simple signal strength test, with the antenna puck 

outside, then inside the fuselage?



Charlie



-- 

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_________________
Charlie

rowlandcarson(at)gmail.co
Guest

Posted: Sat Nov 07, 2020 8:43 am Post subject: gps antenna under glassfibre?

On 2020-11-07, at 16:12, Charlie England <ceengland7(at)gmail.com> wrote:



 	  Quote: 	
		   Can you push the fuselage outdoors and do a simple signal strength test, with the antenna puck outside, then inside the fuselage?


	




Charlie - thanks for pointing out the really obvious thought that I had totally missed! As I said, I’m still considering purchase, so I don’t have the actual hardware, but I can easily do a comparison using the GPS diagnostic app(s) on my phone.



in friendship



Rowland



| Rowland Carson          ... that's Rowland with a 'w' ...

| <rowlandcarson(at)gmail.com>            http://www.rowlandcarson.org.uk

| Skype, Twitter: rowland_carson      Facebook: Rowland Carson

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Nov 07, 2020 6:50 pm Post subject: gps antenna under glassfibre?

 	  Quote: 	
		    	  Quote: 	
		  Rowland 	
 As a data point, many RV-x builders mount a small metal shelf on the hot side of the firewall, just under the 'glass cowl. As long as there isn't a lot of carbon in the structure, or a lot of metal in the paint, it should work fine inside the structure. Can you push the fuselage outdoors and do a simple signal strength test, with the antenna puck outside, then inside the fuselage?



 Charlie 	


    Bingo . . . when in doubt . . . measure!



 

   Bob . . .

bobnoffs

Joined: 04 Jul 2012
Posts: 132
Location: northern wi.

Posted: Mon Nov 09, 2020 5:26 am Post subject: Re: gps antenna under glassfibre?

what happens if the antennas are right next to each other? it absolutely will hurt reception,or it might and it's not recommended? does anyone have experience with 2 antennas next to each other?

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Nov 09, 2020 6:12 am Post subject: gps antenna under glassfibre?

At 07:26 AM 11/9/2020, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "bobnoffs" <icubob(at)gmail.com>



 what happens if the antennas are right next to each other? it absolutely will hurt reception,or it might and it's not recommended? does anyone have experience with 2 antennas next to each other?



 	


   Receive-only antennas at near microwave frequencies

   are not interactive. They work fine in close proximity.



 

 

   Bob . . .

rparigoris

Joined: 24 Nov 2009
Posts: 792

Posted: Mon Nov 09, 2020 10:01 am Post subject: Re: gps antenna under glassfibre?

Hi Rowland I have an XS mono I with most of my antennas installed and needed to add ADS-B. The Garmin GA-35 antenna install manual wants a ground plane (Bob can't quite figure out why). Anyway I have a Dynon magnetometer in my ceiling and the GA-35 would need a clearance pocket if I did install in ceiling. Anyway I made up a 8 pointed ground plane that will also be used as an antenna mount and installing it just forward of the baggage bay bulkhead under the top of fuse. I will not install it absolute level with fuse but aim the forward up a little. Looks not too bad. https://1drv.ms/u/s!Ah1S270Nwg9V3SI7_BpEe0ECaWIV?e=cVFSGb I will bend radials to follow the bottom of ceiling except for the front ones and mount using a screw on each radial about 1/3 in from tip going into a G-10 rod bonded to the ceiling. The front facing radial will be ~ 2 fingers below the ceiling. Ron P.

rowlandcarson(at)gmail.co
Guest

Posted: Mon Nov 09, 2020 1:07 pm Post subject: gps antenna under glassfibre?

On 2020-11-09, at 14:11, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com> wrote:



 	  Quote: 	
		   At 07:26 AM 11/9/2020, you wrote:


	


 	  Quote: 	
		  > what happens if the antennas are right next to each other? it absolutely will hurt reception,or it might and it's not recommended? does anyone have experience with 2 antennas next to each other?


	


 	  Quote: 	
		     Receive-only antennas at near microwave frequencies

   are not interactive. They work fine in close proximity.


	


Bob - that was my gut feeling too, but I poked around for quite some time and found this spacing chart on the Garmin marine support area:



https://support.garmin.com/en-GB/marine/faq/2svIUDPSDa3M99GT2P1g09/



That was the basis for my 6”/150mm spacing of the antennae already mounted on top of my instrument module.



Since my earlier posting I’ve been in touch with Trig support and they concur with the Garmin advice. The Trig antenna is an active device and claims 26dB gain over a passive antenna. I guess that some of the other ones are also active, and that may be at least part of the reason for the spacing requirement.



I’ve also slept on the question (often a good idea!) and realise that I can attach the TA50 to a small bracket above the parcel shelf (in front of the P2 seat) adjacent to the windscreen edge and that will be fine for both sky view and spacing, although perhaps not the ultimate in elegance!



So, I have this day ordered a TN72/TA50 combo and look forward to getting my 50% CAA rebate on the cast.



Thanks for all the thoughtful responses.



in friendship



Rowland



| Rowland Carson          ... that's Rowland with a 'w' ...

| <rowlandcarson(at)gmail.com>            http://www.rowlandcarson.org.uk

| Skype, Twitter: rowland_carson      Facebook: Rowland Carson

cluros(at)gmail.com
Guest

Posted: Mon Nov 09, 2020 1:33 pm Post subject: gps antenna under glassfibre?

Garmin, Dynon, Trig, and Stratus all state in their installation manuals that GPS antennas must be 6" apart.

I have seen many, many GPS antennas sitting right next to each other working just fine but if I was building a new plane, I would try very hard to follow the installation manuals.

On Mon, Nov 9, 2020 at 1:18 PM Rowland Carson <rowlandcarson(at)gmail.com (rowlandcarson(at)gmail.com)> wrote:

 	  Quote: 	
		  --> AeroElectric-List message posted by: Rowland Carson <rowlandcarson(at)gmail.com (rowlandcarson(at)gmail.com)>

 On 2020-11-09, at 14:11, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

 > At 07:26 AM 11/9/2020, you wrote:

 >> what happens if the antennas are right next to each other? it absolutely will hurt reception,or it might and it's not recommended? does anyone have experience with 2 antennas next to each other?

 >   Receive-only antennas at near microwave frequencies

 >   are not interactive. They work fine in close proximity.

 Bob - that was my gut feeling too, but I poked around for quite some time and found this spacing chart on the Garmin marine support area:

 https://support.garmin.com/en-GB/marine/faq/2svIUDPSDa3M99GT2P1g09/

 That was the basis for my 6”/150mm spacing of the antennae already mounted on top of my instrument module.

 Since my earlier posting I’ve been in touch with Trig support and they concur with the Garmin advice. The Trig antenna is an active device and claims 26dB gain over a passive antenna. I guess that some of the other ones are also active, and that may be at least part of the reason for the spacing requirement.

 I’ve also slept on the question (often a good idea!) and realise that I can attach the TA50 to a small bracket above the parcel shelf (in front of the P2 seat) adjacent to the windscreen edge and that will be fine for both sky view and spacing, although perhaps not the ultimate in elegance!

 So, I have this day ordered a TN72/TA50 combo and look forward to getting my 50% CAA rebate on the cast.

 Thanks for all the thoughtful responses.

 in friendship

 Rowland

 | Rowland Carson          ... that's Rowland with a 'w' ...

 | <rowlandcarson(at)gmail.com (rowlandcarson(at)gmail.com)>            http://www.rowlandcarson.org.uk

 | Skype, Twitter: rowland_carson      Facebook: Rowland Carson

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nuckolls.bob(at)aeroelect
Guest

Posted: Mon Nov 09, 2020 3:31 pm Post subject: gps antenna under glassfibre?

 	  Quote: 	
		  Since my earlier posting I’ve been in touch with Trig support and they concur with the Garmin advice. The Trig antenna is an active device and claims 26dB gain over a passive antenna. I guess that some of the other ones are also active, and that may be at least part of the reason for the spacing requirement.

 	


   That would be a very interesting hypothesis to explore.

   To be sure, there are active devices (transistors)

   in these devices but I cannot wrap my head around the

   idea that they 'radiate' any energy that would cause

   them to compete for real estate.



   Sometimes I wish I still had a desk out at Beech . . .

   I could often get right to the horse's mouth with

   a phone call to the big guys in avionics . . . King

   radio was always VERY helpful and forthcoming.



   It was King engineer that first confirmed my own

   studies suggesting that (1) radio killing spikes

   do not exist in vehicular DC power systems and

   (2) qualification testing of all avionics since

   the 80's has to PROVE that an appliance stands

   off EVERYTHING the airplane might throw at it.

   I.e. avionics master switches were ill-conceived.



   I might know a guy at Garmin that either knows

   or can find out what physics drives that spacing

   suggestion for non-radiating antennas.



   You could do the experiment yourself. Put two

   sets of mounting holes for the 2nd antenna . . .

   one 'snuggled up' to the first and the second

   one 'socially distanced'. See if you can observe

   any differences.



 

   Bob . . .

rowlandcarson(at)gmail.co
Guest

Posted: Tue Nov 10, 2020 7:15 am Post subject: gps antenna under glassfibre?

On 2020-11-09, at 23:29, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com> wrote:



 	  Quote: 	
		     You could do the experiment yourself. Put two

   sets of mounting holes for the 2nd antenna . . .

   one 'snuggled up' to the first and the second

   one 'socially distanced'. See if you can observe

   any differences.


	




Bob - good suggestion, but I now have a working solution that honours the makers’ recommendations, and life is too short!



As it used to say in in the maths books “it is left as an exercise for the student to . . .”.



in friendship



Rowland



| Rowland Carson          ... that's Rowland with a 'w' ...

| <rowlandcarson(at)gmail.com>            http://www.rowlandcarson.org.uk

| Skype, Twitter: rowland_carson      Facebook: Rowland Carson

nuckolls.bob(at)aeroelect
Guest

Posted: Tue Nov 10, 2020 10:09 am Post subject: gps antenna under glassfibre?

 	  Quote: 	
		  Bob - good suggestion, but I now have a working solution that

 honours the makers’ recommendations, and life is too short!



 As it used to say in in the maths books “it is left as an

 exercise for the student to . . .”.

 	




   Understand and can't disagree . . . I don't

   have DATA.  We used to gather a lot of data

   in the TC houses . . . but that practice

   faded to a fraction of what it was by time

   I left. What was that old adage . . . "if

   you don't have time to do it right the first

   time, where will you find the time to do it

   over?"



   I think I related a story about ELT's throwing

   and error code to high VSWR on the vhf antenna.

   Found some badly abused antennas jammed under

   the vertical fin fairing toe cap . . . I proposed

   some short, top loaded antennas that would have

   thrived in that location. No time. They talked

   the ELT manufacturer into widening the 'acceptable

   SWR limits' and guess what . . . the red light

   went out . . . (sigh)



   I'm wondering if any empirical data was used

   to generate that list of spacings?



 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

chasb(at)satx.rr.com
Guest

Posted: Wed Nov 11, 2020 6:13 am Post subject: gps antenna under glassfibre?

My RV-6A has operated with an Apollo SL-60 GPS antenna under the fiberglass cowl for nearly 15 years. No problems. About two years ago, I added an echoUAT ADS-B unit with a uAvionix SkyFYX GPS Antenna under the cowl. It is mounted within ¼ inch of the previous antenna. Also works with no problems. Both antennas sit on a small bracket riveted to the engine side of the firewall. The SkyFYX is more than an antenna, it is also a complete WAAS GPS packaged in an antenna sized component. The installation manual had no recommendations or limitations as to antenna location or proximity to other antennas. 

Charlie Brame

RV-6A, N11CB

San Antonio

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Nov 11, 2020 7:23 am Post subject: gps antenna under glassfibre?

At 08:12 AM 11/11/2020, you wrote:

  	  Quote: 	
		  My RV-6A has operated with an Apollo SL-60 GPS antenna under the fiberglass cowl for nearly 15 years. No problems. About two years ago, I added an echoUAT ADS-B unit with a uAvionix SkyFYX GPS Antenna under the cowl. It is mounted within ¼ inch of the previous antenna. Also works with no problems. Both antennas sit on a small bracket riveted to the engine side of the firewall. The SkyFYX is more than an antenna, it is also a complete WAAS GPS packaged in an antenna sized component. The installation manual had no recommendations or limitations as to antenna location or proximity to other antennas. 



 Charlie Brame

 RV-6A, N11CB

 San Antonio 	


    Good data . . . thanks!



 

 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

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