VansAirForceForums  
Home > VansAirForceForums

-POSTING RULES
-Advertise in here!
- Today's Posts | Insert Pics

Keep VAF Going
Donate methods

Point your
camera app here
to donate fast.


Go Back   VAF Forums > Avionics / Interiors / Fiberglass > GPS
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 02-08-2021, 02:43 PM
Flying Canuck Flying Canuck is offline
 
Join Date: Jan 2015
Location: Red Deer, Alberta, Canada
Posts: 503
Default GPS Antenna - on or under the cowling

I finally got my GPS 175 that I ordered in November but have not been able to decide where I'm installing the GA 35 antenna. It's down to 2 options separated by 2 or 3 inches vertically. As far forward on the center of the cowling that I can, aft of the rear baffles. Only question is if I take the easy route and install it visible on top or if I come up with a bracket and put it underneath the cowling.

I know that both have been done and are feasible, is there anyone with experiences that might help me decide? I think I'm leaning towards under just because it will look so much better, but any performance concerns?

Thoughts anyone?
__________________
Claude Pitre
RV-9A #91081, C-GCPT
Dynon SkyView HDX, IO-320 and WW 200RV C/S. Flying as of August 6, 2018

Added GPS 175 and authorized for IFR April 1, 2021

Interactive map of all of my flights here
Reply With Quote
  #2  
Old 02-08-2021, 02:50 PM
bjdecker's Avatar
bjdecker bjdecker is offline
 
Join Date: Jun 2005
Location: Georgetown, TX
Posts: 533
Default Well....

There's some anecdotal evidence that active electronics suffer shortened life spans due to the heat under the cowling.

I chose to make fiberglass panels for the "boot cowl" and undermount the GPS & SXM antennas.
Attached Thumbnails
Click image for larger version

Name:	IMG_1104.jpg
Views:	169
Size:	427.6 KB
ID:	8094  Click image for larger version

Name:	IMG_0855.jpg
Views:	210
Size:	276.6 KB
ID:	8096  Click image for larger version

Name:	IMG_0854.jpg
Views:	192
Size:	300.0 KB
ID:	8098  Click image for larger version

Name:	IMG_0886.jpg
Views:	263
Size:	231.1 KB
ID:	8099  
__________________
Brian Decker
Retired Firmware Guy and Airplane Builder

2020 RV-14 QB -- Under construction - Tailcone & Empennage Complete.
2018 RV-7 QB -- Built, Flying
2007 RV-7 QB -- Built, Drowned, Resurrected and flying
1998 RV-8 QB -- Started, Sold
1986 Mooney 205SE
1980 Mooney 231

Aided and abetted building a number of other RV's.
Reply With Quote
  #3  
Old 02-08-2021, 03:08 PM
Flying Canuck Flying Canuck is offline
 
Join Date: Jan 2015
Location: Red Deer, Alberta, Canada
Posts: 503
Default

That's an interesting idea. I've already the access panels there, I could mount on top of one - although I'd have to watch for clearance from a GPS antenna on my glare shield. For putting it under a new fiberglass panel, I'd be concerned about two things, I'm not great with fiberglass fabrication and the fact that only the panel above is fiberglass, would that limit reception from angles that don't go through the fiberglass? That would be only shallow angles, so maybe it's fine. Do you have this installation flying?

I like the toaster attachment in your last picture.
__________________
Claude Pitre
RV-9A #91081, C-GCPT
Dynon SkyView HDX, IO-320 and WW 200RV C/S. Flying as of August 6, 2018

Added GPS 175 and authorized for IFR April 1, 2021

Interactive map of all of my flights here

Last edited by Flying Canuck : 02-08-2021 at 03:12 PM. Reason: more details
Reply With Quote
  #4  
Old 02-08-2021, 03:18 PM
bjdecker's Avatar
bjdecker bjdecker is offline
 
Join Date: Jun 2005
Location: Georgetown, TX
Posts: 533
Default

Quote:
Originally Posted by Flying Canuck View Post
I like the toaster attachment in your last picture.
I was working on the kitchen counter -- which my wife just loves

GPS reception is solid, 12+ satellites with >3 bars each & 3d Diff. I have over 1000 flight hours now with GNS430W and GTN650Xi in two different RV-7s with this solution.

IIRC there is a <1 masking to the front, 5 above the horizon to the sides, and 25 to the rear. However, with 31 satellites in the constellation, that small of a masking doesn't present an operational problem.
__________________
Brian Decker
Retired Firmware Guy and Airplane Builder

2020 RV-14 QB -- Under construction - Tailcone & Empennage Complete.
2018 RV-7 QB -- Built, Flying
2007 RV-7 QB -- Built, Drowned, Resurrected and flying
1998 RV-8 QB -- Started, Sold
1986 Mooney 205SE
1980 Mooney 231

Aided and abetted building a number of other RV's.

Last edited by bjdecker : 02-08-2021 at 03:46 PM. Reason: Added mask angle
Reply With Quote
  #5  
Old 02-08-2021, 03:35 PM
Freakshow108's Avatar
Freakshow108 Freakshow108 is online now
 
Join Date: Sep 2018
Location: Eatonville WA
Posts: 141
Default

Quote:
Originally Posted by bjdecker View Post
There's some anecdotal evidence that active electronics suffer shortened life spans due to the heat under the cowling.

I chose to make fiberglass panels for the "boot cowl" and undermount the GPS & SXM antennas.
Do you mind if I steal this idea??
Reply With Quote
  #6  
Old 02-08-2021, 03:35 PM
bjdecker's Avatar
bjdecker bjdecker is offline
 
Join Date: Jun 2005
Location: Georgetown, TX
Posts: 533
Default

Quote:
Originally Posted by Freakshow108 View Post
Do you mind if I steal this idea??
I'd be honored
__________________
Brian Decker
Retired Firmware Guy and Airplane Builder

2020 RV-14 QB -- Under construction - Tailcone & Empennage Complete.
2018 RV-7 QB -- Built, Flying
2007 RV-7 QB -- Built, Drowned, Resurrected and flying
1998 RV-8 QB -- Started, Sold
1986 Mooney 205SE
1980 Mooney 231

Aided and abetted building a number of other RV's.
Reply With Quote
  #7  
Old 02-08-2021, 03:43 PM
sf3543 sf3543 is offline
 
Join Date: Jan 2005
Location: San Antonio, TX
Posts: 1,071
Default

When mounting GPS antennas, remember that they do not only look straight up to see satellites but also look at angles to pick up satellites closer to the horizon. So you don't want to shade the areas around the antenna and block off part of the search area. Make sure your panel opening is large enough to permit this.
I prefer mounting on a shelf in front of the FW as close to the underside of the cowling as possible, and about 6" in front of the FW, especially for WAAS antennas. This minimizes the shading from the fuselage behind the antenna.
__________________
Steve Formhals
A&P, Tech Counselor & Flight Advisor
RV3B
RV8
Reply With Quote
  #8  
Old 02-08-2021, 05:08 PM
BobTurner BobTurner is offline
 
Join Date: Dec 2011
Location: Livermore, CA
Posts: 7,292
Default

Since you (the OP) are in Canada you may wish to check with Transport Canada. I know some of your IFR rules are different than the US's, e.g., 2 separate navigation boxes. If TC says you must install the 175 in accordance with the Garmin installation manual, then you're out of luck with any of the hidden locations previously mentioned, as, IIRC, that manual doesn't authorize them. Here in the US the FAA doesn't seem to care, at least not for EAB.
Reply With Quote
  #9  
Old 02-08-2021, 05:22 PM
Flying Canuck Flying Canuck is offline
 
Join Date: Jan 2015
Location: Red Deer, Alberta, Canada
Posts: 503
Default

My reading of the CARs didn't catch any mention of installation requirements. The GPS175 installation manual gives the following guidance for antenna installation and nothing much more.

Quote:
The GPS antenna should:
1. Be installed as near to level as possible with respect to the normal cruise flight attitude of the aircraft.
2. Be installed in a location to minimize the effects of airframe shadowing during typical maneuvers.
3. Be installed a minimum of two feet from any VHF COM antenna or any other antenna which may emit harmonic
interference at the L1 frequency of 1575.42 MHz.
4. Be installed a minimum of two feet from any antennas emitting more than 25 watts.
5. Be installed a minimum of nine inches (center to center) from other antennas, including passive antennas such as
another GPS or XM antenna.
6. Be installed a minimum of three inches from the windscreen.
7. Have a twelve inch center to center spacing between GPS antennas.
This doesn't say anything about hidden installations as long as airframe shadowing is minimized (#2).
__________________
Claude Pitre
RV-9A #91081, C-GCPT
Dynon SkyView HDX, IO-320 and WW 200RV C/S. Flying as of August 6, 2018

Added GPS 175 and authorized for IFR April 1, 2021

Interactive map of all of my flights here
Reply With Quote
  #10  
Old 02-08-2021, 05:40 PM
Tankerpilot75's Avatar
Tankerpilot75 Tankerpilot75 is offline
 
Join Date: Jan 2015
Location: Oklahoma City, OK
Posts: 613
Default

Claude,

I’ve three gps antennas installed on the firewall directly below the cowl and meet the criteria you referenced above. Two non-WAAS units were installed by the builder for the dual 430s in 2008. Two years ago I installed a WAAS antenna between the non-WAAS antennas for my Garmin 335 transponder. Haven’t had any trouble with them at all.

I do recommend you make sure the mounting brackets you use are secured to the firewall using nut plates so it will be easier to remove them for access to things like your battery, hose replacement, wiring or cables. I really like the setup I use.

Jim
__________________
Jim Harris, ATP, T38, EC/KC-135A/E/R, 2008 RV7A, 2nd owner, N523RM (2015)
Superior XPIO-360, Hartzel CS prop, Dual GRT Horizon WS, EIS, Garmin 340, 335 w/WAAS gps, Dual 430s (non-WAAS), TruTrak 385 A/P with auto-level & auto-trim, Tosten 6 button Military Grips, FlightBox wired to WS, Dynon D10A w/battery backup, 406 MHz ELT. Custom Interior, New TS Flightline hoses, Great POH!
Retired - Living the dream - going broke!

Last edited by Tankerpilot75 : 02-08-2021 at 05:43 PM.
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 08:15 AM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.