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What can GPS and XM antennas see through?

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cskelt(at)earthlink.net
Guest

Posted: Sun May 03, 2009 2:19 pm Post subject: What can GPS and XM antennas see through?

Folks, I'm installing a Garmin 496 in my Lancair 320.  The Garmin manual suggests placing the GPS and XM antennas supplied with the unit where they can see the sky through the canopy.  This could be achieved by placing the two devices on the glare shield.  However it would be an easier installation if I were to place the two antennas below the glare shield.  This way, there'd be no awkward electrical connections to deal with when removing or replacing the glare shield.  If the antennas can see through perspex, (or laminated auto glass) can they additionally see through the skinny fiberglass molding covered with headlining material?  Thanks in advance for any advice. 

  

 Chris Skelt.

 __________________

 cskelt(at)earthlink.net (cskelt(at)earthlink.net)

 

  [quote][b]

BobsV35B(at)aol.com
Guest

Posted: Sun May 03, 2009 2:38 pm Post subject: What can GPS and XM antennas see through?

Good Evening Chris,

  

 The antennas will look through that glareshield just fine. However, you  must remember that any distance below the very top of the airplane will reduce  the amount of sky that can be seen via the antennas.

  

 We have found that antennas mounted on top of the glove box and under the  glareshield work reasonably well in various Bonanzas.

  

 Happy  Skies



Old Bob

AKA

Bob Siegfried

Ancient Aviator

628 West 86th  Street

Downers Grove, IL 60516

630 985-8502 

Stearman  N3977A

Brookeridge Air Park LL22   

  In a message dated 5/3/2009 5:21:28 P.M. Central Daylight Time,  cskelt(at)earthlink.net writes:

  	  Quote: 	
		     

   Folks, I'm installing a Garmin 496 in my Lancair 320.  The Garmin    manual suggests placing the GPS and XM antennas supplied with the    unit where they can see the sky through the canopy.  This could be    achieved by placing the two devices on the glare shield.  However it    would be an easier installation if I were to place the two antennas below the    glare shield.  This way, there'd be no awkward electrical    connections to deal with when removing or replacing the glare shield.  If    the antennas can see through perspex, (or laminated auto glass) can    they additionally see through the skinny fiberglass molding    covered with headlining material?  Thanks in advance for any advice.    

    

   Chris Skelt.

   __________________

   cskelt(at)earthlink.net (cskelt(at)earthlink.net)

   

 	  Quote: 	
		  



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  [quote][b]

mrspudandcompany(at)veriz
Guest

Posted: Sun May 03, 2009 3:10 pm Post subject: What can GPS and XM antennas see through?

Are there any published specs as to what materials, at what thickness, satellite antennas can see through without a large attenuation of signal strength?  If so can you point me toward them?  

   

Thanks,  

   

Roger  

   

   

   

   

   

Good Evening Chris,  

    

   

    

The antennas will look through that glareshield just fine. However, you must remember that any distance below the very top of the airplane will reduce the amount of sky that can be seen via the antennas.  

    

   

    

We have found that antennas mounted on top of the glove box and under the glareshield work reasonably well in various Bonanzas.  

    

   

    

Happy Skies

 

 Old Bob

      

   

      

In a message dated 5/3/2009 5:21:28 P.M. Central Daylight Time, cskelt(at)earthlink.net writes:  

  [quote]    

Folks, I'm installing a Garmin 496 in my Lancair 320.  The Garmin manual suggests placing the GPS and XM antennas supplied with the unit where they can see the sky through the canopy.  This could be achieved by placing the two devices on the glare shield.  However it would be an easier installation if I were to place the two antennas below the glare shield.  This way, there'd be no awkward electrical connections to deal with when removing or replacing the glare shield.  If the antennas can see through perspex, (or laminated auto glass) can they additionally see through the skinny fiberglass molding covered with headlining material?  Thanks in advance for any advice.   

    

   

    

Chris Skelt.  

    

__________________  

   [b]

BobsV35B(at)aol.com
Guest

Posted: Sun May 03, 2009 4:10 pm Post subject: What can GPS and XM antennas see through?

Good Evening Roger,

  

 If such a document exists, I am not aware of it!

  

 Do Not Archive

  

 Happy  Skies



Old Bob

AKA

Bob Siegfried

Ancient Aviator

628 West 86th  Street

Downers Grove, IL 60516

630 985-8502 

Stearman  N3977A

Brookeridge Air Park LL22   

  In a message dated 5/3/2009 6:12:52 P.M. Central Daylight Time,  mrspudandcompany(at)verizon.net writes:

  	  Quote: 	
		     

Are    there any published specs as to what materials, at what thickness, satellite    antennas can see through without a large attenuation of signal strength?     If so can you point me toward them?   

    

Thanks,   

    

Roger 	




 The Average US Credit Score is 692. See Yours in Just 2 Easy Steps!

  [quote][b]

mrspudandcompany(at)veriz
Guest

Posted: Sun May 03, 2009 5:34 pm Post subject: What can GPS and XM antennas see through?

Good Evening Roger,  

    

   

    

If such a document exists, I am not aware of it!  

    

   

    

Do Not Archive  

    

   

  [quote]Happy Skies



Old Bob



 Hi Bob, Apparently the GPS antenna can see through some plastics and light foam but not through wood, metal, dense foam, or carbon fiber, to name a few.It seems your best bet is to have nothing but air between the antenna and satellite, for best reception. Roger [b]

Dick Sipp

Joined: 11 Jan 2006
Posts: 215
Location: Hope, MI

Posted: Sun May 03, 2009 7:26 pm Post subject: What can GPS and XM antennas see through?

I have these antennas mounted ahead of the firewall under  the ~1/8 thick painted fiberglass cowling.  No problems at one year in  service.

 I believe this is a relatively common practice in the RV  community.

  

 Dick Sipp

 RV10 N110DV

 [quote] [b]

bakerocb

Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA

Posted: Mon May 04, 2009 2:55 am Post subject: What can GPS and XM antennas see through?

5/4/2009



Hello Chris, When I discussed this subject with a Garmin technical rep he 

said that placing the antenna for my GNS 430 inside the fiberglass fuselage 

molding of my KIS TR-1 should not be a problem, but that mounting the 

antenna on an aluminum plate would help shield the antenna from 

electromagnetic noise coming from below.



I mounted the antenna on an aluminum shelf inside the fuselage molding 

between the firewall and the instrument panel (lots of electromagnetic 

generating stuff in that area). The installation has worked perfectly -- I 

now have a 430W antenna in that location.



'OC' Says: "The best investment we can make is the effort to gather and 

understand knowledge."



====================================================



Time: 03:19:57 PM PST US

From: "cskelt(at)earthlink.net" <cskelt(at)earthlink.net>

Subject: What can GPS and XM antennas see through?



Folks, I'm installing a Garmin 496 in my Lancair 320.  The Garmin manual 

suggests

placing the GPS and XM antennas supplied with the unit where they can see 

the

sky through the canopy.  This could be achieved by placing the two devices

on the glare shield.  However it would be an easier installation if I were 

to

place the two antennas below the glare shield.  This way, there'd be no 

awkward

electrical connections to deal with when removing or replacing the glare 

shield.

If the antennas can see through perspex, (or laminated auto glass) can they

additionally see through the skinny fiberglass molding covered with 

headlining

material?  Thanks in advance for any advice.



Chris Skelt.

rduplooy(at)iafrica.com
Guest

Posted: Mon May 04, 2009 7:04 am Post subject: What can GPS and XM antennas see through?

Our Rv-4 has the antenna mounted in the same place ( As Dick Sipp- FWF under 

fibreglass cowling)  for the Garmin XL250...



Aquires satellites quickly, and navigates faultlessly to destinations...even 

after 300 hrs.



Robert du Plooy

 	  Quote: 	
		   >

 I have these antennas mounted ahead of the firewall under the ~1/8 thick

 painted fiberglass cowling.  No problems at one year in service.

 I believe this is a relatively common practice in the RV community.



 Dick Sipp

 RV10 N110DV



 >

mchristian(at)canetics.co
Guest

Posted: Mon May 04, 2009 8:12 am Post subject: What can GPS and XM antennas see through?

On my Cirrus, the two GPS antennas are velcro'd to the underneath of the glareshield and they work just fine.



Mike

skywagon

Joined: 11 Feb 2006
Posts: 184

Posted: Mon May 04, 2009 9:24 am Post subject: What can GPS and XM antennas see through?

All GPS antennas and receivers are not the same as we all know.  Most do not 

like to have their antennas "shielded" by anything.  That can includes ice 

and snow too.



And, there are GPS units that use receivers so sensitive, they work just 

fine inside a building.  Take the little Garmin portable, 60CSx is one.  I 

do not know what gps chip set it uses, but, that little unit is a 100 fold 

more sensitive than our multi-thousand dollar units.  Put it in your pocket 

or lunch box, sit under a grove of trees and it keeps ticking.   So, go with 

the factory recommendation and give the antenna a free view of the sky.

David

---

cskelt(at)earthlink.net
Guest

Posted: Sat May 09, 2009 4:47 am Post subject: What can GPS and XM antennas see through?

Folks,

 This is to thank all of you who replied to the list and to me personally.  

  

 The consensus on the Internet is that GPS signals run around 1.5 GHz and XM Weather at about 2.3 GHz with corresponding wavelengths of about 20 cm and 13 cm respectively.  This is more than an order of magnitude higher than the frequencies we use for COM and NAV, and so, all other things being equal, we shouldn't expect them to penetrate so much of the same solid material -- which was my original concern, particularly as I have no data on the relative transmissivity of perspex (that we understand is OK) and fiberglass (that's probably OK, but I don't know).  Even if I can get a good GPS or XM reading while stationary in the driveway, that doesn't necessarily translate into good navigation at cruise speed, and that is why positive and negative experiences from a large user community are worth much more than guidelines from the installation manual.  It seems there are many good functional ways of doing the installation, and some   useful considerations to take into account. Thanks again.

  

 Regards, Chris. 

  

  

 __________________

 cskelt(at)earthlink.net (cskelt(at)earthlink.net)

 Chris Skelt

  

 

  [quote][b]

lists(at)stevet.net
Guest

Posted: Sat May 09, 2009 6:06 am Post subject: What can GPS and XM antennas see through?

Chris,

I am not flying yet, and my experience is anecdotal so take this for what it's worth.  I am building a Glasair Super II RG, all fiberglass fuselage.  The construction is glass over foam sandwich.  I have my XM and GPS antennae on a shelf at the inside-top of the aft fuselage and the airplane is inside my garage.  When I fire up my panel, I can successfully pick up both the XM and GPS signal.  It does take a while to lock on, and the signal is weak, but it is there.  So, both signals are able to penetrate the garage roof, the ceiling, and the fiberglass body.  Now I suppose I cannot tell how much is coming through the windows and open garage door, but that is my experience.





 Steve

________________________________________________________________________

 



On May 9, 2009, at 5:44 AM, cskelt(at)earthlink.net (cskelt(at)earthlink.net) wrote:

[quote] 

Folks,

 This is to thank all of you who replied to the list and to me personally.  

  

 The consensus on the Internet is that GPS signals run around 1.5 GHz and XM Weather at about 2.3 GHz with corresponding wavelengths of about 20 cm and 13 cm respectively.  This is more than an order of magnitude higher than the frequencies we use for COM and NAV, and so, all other things being equal, we shouldn't expect them to penetrate so much of the same solid material -- which was my original concern, particularly as I have no data on the relative transmissivity of perspex (that we understand is OK) and fiberglass (that's probably OK, but I don't know).  Even if I can get a good GPS or XM reading while stationary in the driveway, that doesn't necessarily translate into good navigation at cruise speed, and that is why positive and negative experiences from a large user community are worth much more than guidelines from the installation manual.  It seems there are many good functional ways of doing the installation, and some  useful considerations to take into account. Thanks again.

  

 Regards, Chris. 

  

  

 __________________

 cskelt(at)earthlink.net (cskelt(at)earthlink.net)

 Chris Skelt

  

 	  Quote: 	
		  	


[b]

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