GPS antenna placement on an -8

[TheNewGuy]

I’ll be installing a Garmin GPS in the next few weeks and am trying to decide on a good mounting location for the antenna. I’ve seen a few discussions on VAF but haven’t found much beyond mounting in the engine compartment.

A gentleman at my airport with a fastback -8 has his mounted on the engine mount above the mags. Fabricating a bracket for the firewall or engine mount seems like a clean solution, but is that actually a good location in practice? Has anyone had issues with reception or found a better spot?

If the engine compartment location works well, I’d be inclined to go that route.

Thanks.

 

[skirting_virga]

Following. I wanted to put it in back but under the cowling seems more convenient. I'm wondering about interference with things like automotive style plug leads and such.

 

[Mark Dickens]

I’ll be installing a Garmin GPS in the next few weeks and am trying to decide on a good mounting location for the antenna. I’ve seen a few discussions on VAF but haven’t found much beyond mounting in the engine compartment.

A gentleman at my airport with a fastback -8 has his mounted on the engine mount above the mags. Fabricating a bracket for the firewall or engine mount seems like a clean solution, but is that actually a good location in practice? Has anyone had issues with reception or found a better spot?

If the engine compartment location works well, I’d be inclined to go that route.

Thanks.

I mounted my Garmin GPS antenna under the cowl and never had an issue.

 

[Mark Dickens]

I would add to the above, that I did have issues mounting a Dynon GPS-250 antenna (the pre-ADSB version). alongside the Garmin antenna under the cowl when after a fuel stop the heat would cause the Dynon antenna to be non-functional until after the engine restart and it cooled down. This always corrected itself on the taxi down to the runway.

 

[TheNewGuy]

I would add to the above, that I did have issues mounting a Dynon GPS-250 antenna (the pre-ADSB version). alongside the Garmin antenna under the cowl when after a fuel stop the heat would cause the Dynon antenna to be non-functional until after the engine restart and it cooled down. This always corrected itself on the taxi down to the runway.

I’m not familiar with Dynon GPS. Is it inferior in that regard? I did see this article about mounting under the canopy

Mounting On a Curve - KITPLANES

A long time ago, when homebuilders began installing Garmin 430s—the most popular IFR GPS/nav/com of the day—we were mostly left on our own to install the somewhat large GPS antenna. Garmin’s most important instruction was “DO NOT PAINT,” as proclaimed on the antenna itself. Many of us decided...

www.kitplanes.com

 

[Carl Froehlich]

For the RV-8 aft of the rear seat for the “sensitive” Garmin antenna. This spot meets all the Garmin rules. For the Dynon GPS 250 or GPS 2020, on the glare shield covered with piece of dark cloth to eliminate glare.

Carl

 

[TheNewGuy]

For the RV-8 aft of the rear seat for the “sensitive” Garmin antenna. This spot meets all the Garmin rules. For the Dynon GPS 250 or GPS 2020, on the glare shield covered with piece of dark cloth to eliminate glare.

Carl

Thanks Carl. How did you achieve a snug fit with the Garmin antenna against the curved body?

 

[RV8Squaz]

I’ve got mine on a shelf attached to the firewall several inches left of center. Never an issue in almost 20 years of flying. I had a 430 and now a 650xi.

 

[Carl Froehlich]

Thanks Carl. How did you achieve a snug fit with the Garmin antenna against the curved body?

Easy, it is pretty close if you do nothing. But add a washer on each of the screws on the “down” side of the fuselage between the antenna puck and the fuselage if you want it be exact.

Carl

 

[Ironflight]

A lot of us (not all) had our 430 antennas under the cowl until they came out with the 430W - and the WAAS antenna did not like looking backawards through the firewall. Lots of dropouts, and since many were flying IFR, lots of antennas got moved to the turtle-deck, under the canopy, behind the passenger. I’ve had excellent performance there, and mounted the RV-3’s antenna in the same spot - and did the same sort of thing with the Rocket, except that’s a Fastback, so it went behind the rear canopy skirt. Mounting on a curve isn’t terribly hard - a little resin and micro and it goes on easy. I wrote an article for KP on it but you’ll have to search for it. On the Rocket I did it easier - used a high density neoprene material from McMaster - the antenna screws compressed it in the middle, left it thicker on the sides. Trimmed it with a razor blade and it looks (and works) fine.

 

[TheNewGuy]

A lot of us (not all) had our 430 antennas under the cowl until they came out with the 430W - and the WAAS antenna did not like looking backawards through the firewall. Lots of dropouts, and since many were flying IFR, lots of antennas got moved to the turtle-deck, under the canopy, behind the passenger. I’ve had excellent performance there, and mounted the RV-3’s antenna in the same spot - and did the same sort of thing with the Rocket, except that’s a Fastback, so it went behind the rear canopy skirt. Mounting on a curve isn’t terribly hard - a little resin and micro and it goes on easy. I wrote an article for KP on it but you’ll have to search for it. On the Rocket I did it easier - used a high density neoprene material from McMaster - the antenna screws compressed it in the middle, left it thicker on the sides. Trimmed it with a razor blade and it looks (and works) fine.

Thanks for the reply. You must be Paul. I attached your article above after reading. I was thinking about Neoprene or some sort of rubber agent instead of the resin.

 

[skirting_virga]

Mounting on a curve isn’t terribly hard - a little resin and micro and it goes on easy. I wrote an article for KP on it but you’ll have to search for it.

Love your article, but my confidence with resin on a painted airplane is low. I'll probably have to buy some materials and mess around a bit, but that's exactly where I want it and exactly how I would like to do it.

I bet I could 3D print something, but it would be worse, and probably require a couple revisions without a way to measure the curve exactly.

 

[Ironflight]

Love your article, but my confidence with resin on a painted airplane is low. I'll probably have to buy some materials and mess around a bit, but that's exactly where I want it and exactly how I would like to do it.

I bet I could 3D print something, but it would be worse, and probably require a couple revisions without a way to measure the curve exactly.

Try the sheet neoprene (with adhesive) from McMaster - that’s what I did on the Rocket and it has greater curvature than the -8 in that spot. I think I used 1/4” thick material. Easier and less permanent than the micro version. We learn with every airplane we do….

 

[skirting_virga]

Try the sheet neoprene (with adhesive) from McMaster - that’s what I did on the Rocket and it has greater curvature than the -8 in that spot.

Adhesive down to the skin or up to the antenna? I see you painted the antenna...

 

[RV8iator]

Interesting timing on this post. I’ve had my GTN650 GA35 GPS WAAS antennae mounted under cowl atop engine mount since 2012 and a couple thousand hours problem free.
Until last week.
I was headed down to KCRG to Bragg avionics for my 24 month XPNDR check and climbing through 300 feet lost 11 out of 15 Satellites completely and the other 4turned Blue. Bam, no magenta line. Good thing I could actually see the SSI VOR under me so didn’t panic. My other several GPSs had strong locks.
Intermittent reception the remainder on the quick flight on 650.
Talked to the avionics tech working with me and showed him photos of the Status page. We talked about cleaning connections, checking coax, all the usual fixes but the 650 had just been taking a bit longer to locate itself and I had already cleaned and checked the coax.
Bragg had a brand new GA35 and it wasn’t even half an airplane unit so in the cart it went. They even offered to install it, but I was too lazy to pull the cowl and my labor was a LOT less than the very efficient and friendly techs there.
Back home, cowl off, 15 minutes to gather tools and replace the antennae and reinstall the cowl and, voila, 15 stable satellites.
So, to remain with the placement thread, I hope this GA35 lasts as long under the cowl as the first one did.

 

[Ironflight]

Adhesive down to the skin or up to the antenna? I see you painted the antenna...

Adhesive up - and I won’t tell you WHO painted that antenna……but it works most excellently (very strong signal on all satellites). And before the comments - I have chatted up a number of antenna engineers who didn’t run away screaming…..

 

[TheNewGuy]

All good info, I’m much obliged. For those who installed under the canopy in the rear, did you also manufacture a doubler plate?

 

[BobTurner]

Interesting timing on this post. I’ve had my GTN650 GA35 GPS WAAS antennae mounted under cowl atop engine mount since 2012 and a couple thousand hours problem free.
Until last week.
I was headed down to KCRG to Bragg avionics for my 24 month XPNDR check and climbing through 300 feet lost 11 out of 15 Satellites completely and the other 4turned Blue. Bam, no magenta line. Good thing I could actually see the SSI VOR under me so didn’t panic. My other several GPSs had strong locks.
Intermittent reception the remainder on the quick flight on 650.
Talked to the avionics tech working with me and showed him photos of the Status page. We talked about cleaning connections, checking coax, all the usual fixes but the 650 had just been taking a bit longer to locate itself and I had already cleaned and checked the coax.
Bragg had a brand new GA35 and it wasn’t even half an airplane unit so in the cart it went. They even offered to install it, but I was too lazy to pull the cowl and my labor was a LOT less than the very efficient and friendly techs there.
Back home, cowl off, 15 minutes to gather tools and replace the antennae and reinstall the cowl and, voila, 15 stable satellites.
So, to remain with the placement thread, I hope this GA35 lasts as long under the cowl as the first one did.

+1
Okay, I’m so old I remember when the standard procedure for soldering a transistor was to wrap the leads with a wet piece of paper towel, to keep the heat from destroying them.
These days I’m willing to put an active vfr gps antenna under the cowl. But not one used for ifr.

 

[SMRacer]

Perhaps I'm just lazy, because I took the easy way. My Garmin GPS 175 (ADSB out source even though I have the Dynon 2020), GRT MiniX, Dynon 2020, and AFS antennas are ALL on the glare shield. White ones get a covering of black spandex epoxied along the bottom edge. I have NO interference or reception problems with any of the antennas. They are attached to the glare shield with 3M Dual Lock.

 

[Jonnyb]

I think most have them under the cowl on the fire wall or on the back behind the passenger seat.

From reading many of these threads either will work, the only question mark comes from antenna longevity with the heat in the engine compartment.

Take your pick really, whichever is most convenient for your set up.

 

[TheNewGuy]

Despite the extra work, mounting aft of the passenger seems like a more suitable position. Those of you who mounted there, how many feet of RG-400 did you roughly use? SteinAir will be calling today or tomorrow about a harness so id like to add it to my order.

Also, did you run the cable under the floor or along the side of the fuselage?

 

[Carl Froehlich]

Despite the extra work, mounting aft of the passenger seems like a more suitable position. Those of you who mounted there, how many feet of RG-400 did you roughly use? SteinAir will be calling today or tomorrow about a harness so id like to add it to my order.

Also, did you run the cable under the floor or along the side of the fuselage?

Measure your run then add 20% or so. I never measured it, I just get a 100 roll of coax for a new build. You end up using all of it on your plane or when someone else needs a run.

I ran the coax both ways, under the floor on a new build, under the side rails on a retrofit.

Carl

 

[Tall_Order]

A gentleman at my airport with a fastback -8

Assuming you also have a fastback this might be an option to consider also- behind the pilot's right shoulder... as an alternative to under the canopy behind the rear pax for those with the normal slide-back canopy. I've got a non-WAAS IFR navigator's antenna, GRT Sport EX's antenna, and my Android MFD's antennas all located here.

Can't speak to the reception as mine is still an indoor project, but even in the garage and the canopy tipped open, I've been getting reliable 2D position with intermittent 3D for my avionics tests on the IFR navigator. Not saying this is any better than other options, just sharing because I haven't seen anyone else use this spot.

 

[Notso]

Here is what I consider THE best mounting solution to get the antenna out of the way and not mar the exterior. It sits on a bar just under the fiberglass cowling on my RV-8. I had this mount on my current and previous RV-8 and both worked like a champ!

 

[BuckWynd]

I've had my GPS and SIriusXM antennas on a shelf under the cowl for a couple of years now, with zero issues.

(Early construction photo, but you get the idea...)

 

[RV7 To Go]

I stuck mine just behind the canopy rail at the back. Canopy clears just fine. Too much stuff under the cowl already and didn't want to add something that didn't need to be there. Many ways to skin the cat.

 

[RV8JD]

I’ll play.
My RV-8 has the Dynon SV-GPS-2020 mounted on a shelf under the cowl as shown below. Works well. 1730 Hobbs Hours so far with no problems. Don't mount it too close to the firewall such that it is partially blocked. As far as alignment/orientation is concerned, it just has to have a good view of the sky.



Screenshot showing typical GPS fix status. All good, i.e., “Fix Quality: 3D Diff".



My previous RV-8 had a Garmin GPS antenna mounted on the turtledeck under the canopy:

 

[Walt]

"Works Well" is a highly subjective term. It appears many folks are more concerned with cosmetics than performance.

 

[RV8JD]

"Works Well" is a highly subjective term. It appears many folks are more concerned with cosmetics than performance.

I did say “Works well", but backed that up with a screenshot showing my typical GPS fix status, i.e., “Fix Quality: 3D Diff".

From the SkyView Installation Guide:

 

[Nihon_Ni]

I mounted my Garmin WAAS antenna on the glareshield, mostly because I ran out of space in my firewall pass-throughs. I made a little base for it out of epoxy and micro, and pained it black. I covered the antenna in black vinyl because I wasn't as bold as Paul. Since the antenna sits 12" from the navigator, I didn't need the minimum length of RG400, so I just coiled excess under the glareshield.