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GPS Antenna on RV-8 glareshield? Photos wanted.

goatflieg

Well Known Member
It was suggested to me by Jason at Aerotronics that the best compromise location for my GPS puck antenna would be on the glareshield of my RV-8. I've done some preliminary layout work, but the problem is that I don't know exactly where the windscreen will lay on the forward top skin. I've viewed other builder websites, and that's given me some clues... but I won't be cutting my own canopy for quite a while. I'd like to finish the metal work on the forward top skin soon so I can get it painted, but I don't want to drill holes for the puck or the ventilation fans that will flank it until I can be sure the layout will work with the possible windscreen placement. If any other builders have done it this way and can share photos with me, I'd be grateful for the input.
 
This is my current layout. The GPS is top dead center; the fans are as close as practical, and clearance from the instrument panel flange has been taken into consideration.
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Slightly related and a cautionary tale.

If you use a remote GPS antenna for say a G695/795 etc, be careful where you locate it because....... They have a magnetic base !

Ask us how we found out on our RV7 :rolleyes:

So we now subtract 32? from our standby compass - it is easy, honestly !
 
Mine is located under the cowling so can't help with your specific question, but be aware that some GPS manufacturers require a minimum decibel loss (usually caused by the length of coax between the receiver and the antenna) in the coax. Mounting it on the glare shield will require you to engineer that into the installation.
 
Martin,
Have you planned your panel yet? I have a Garmin GMC307 autoflight unit and some annunciator lights located top center of my panel that project into the area where your fans and GPS antenna coax will be. Like Mark, I placed one GPS antenna puck under the cowl on a shelf and another is mounted on a small fabricated platform attached to the turtleback behind the passenger's seat. I'm not flying yet, so I can't say how well my setup will work. Also, while I don't know how much actual interference could result (if any), depending on what avionics you intend to install, some devices may restrict proximity to a fan motor. The installation manual for my GTN650 mentions it, but I don't recall any specific distance requirements.

J. Baker
RV8 Finishing
 
Put mine on the glare shield. Worked fine but covered it with a black tape (instead of flat paint) so it wouldn?t glare on the windscreen. I think I located it after the windscreen was in place.
 
Some comments on your layout:
- For the RV-8, one fan is more than enough and perhaps half the size of what you showing. Put it in the middle.
- Most installs end up with two GPS antennas (e.g. the Dynon 2020 and the Garmin). Put one on each side of the fan equally spaced between the fan and the side of the glaresheild.
- Move everything a little further forward, more like the mid point between the panel and the next bulkhead. Where you have them will cause unnecessary interference with some EFIS and such installs.
- Cover the white antennas with some dark gray or black cloth to eliminate glare. Do not paint.
- Suggestion, for the fan just drill a pattern of holes for the air to go thru, don?t cut a square hole then cover it with a cheap looking grill. The air will go thru just fine.

I built two airplance with both GPS antennas on the glareshield. They both worked perfectly.

Carl
 
To address some comments:
Aerotronics built my panel; Jason knows the layout and approves of the antenna placement and cable length... but I'll check with him about the fan placement.
My panel only requires one GPS antenna and has no standby compass. I got two free fans from Leo Knowlden, so I was going for symmetry there. I do like the thought of using smaller fans, though.
The Garmin puck antenna has "Do Not Paint" marked clearly on top of it, but I've heard otherwise from other experts, so I called Garmin and asked them. They said a thin layer of flat black paint should be fine as long as it's not metallic. They are not aware of any adverse chemical/material issues. Champ, if you have any photos, please share. My main concern is just not knowing how much glare shield space I'll have to work with.
Thanks for the input.
 
SNIP....
My panel only requires one GPS antenna and has no standby compass. I got two free fans from Leo Knowlden, so I was going for symmetry there. I do like the thought of using smaller fans, though. ...SNIP

Keep in mind that the panel you have today will change with time. My first RV-8A had 5 different panel confirguraions in 15 years. The RV-10s first panel lasted just 18 months, and the second panel has been modified twice so far. You will find things to change and who knows what tomorrow brings for avionics.

My point, consider just one smaller fan and the one GPS antenna for now. That leaves your with options to add down the road as compared to two fans when only one is needed.

BTW - fans are dirt cheap. I got a dozen for $20.

Carl
 
Martin - I?m travelling now so sorry I can?t post a picture. I?ll PM you one when I get back wk after next. My Garmin GPS antenna is on centerline about half way between the edge of the instrument panel and the windscreen. No fans though.
 
I covered my entire glairshield with "loop Velcro" and just stuck my antennas, gate opener, and pen up there.

The black Velcro feels like felt and has held up very well.

Contact me off list, I bought a bolt of the stuff years ago and have been selling to builders and may still have some left over.
 
Now the velcro loop idea doesn't sound half bad. The more I think about it the more I like it. It is kind of like a custom dash mat they sell for automobiles but with a true pupose.

Just when I thought I'd heard of everything. Thanks Bill R.

I might just try it.

Jim
 
gpsantennas.jpg


I was wondering about having them in my vision, I fly a Champ with an aera sitting on the glaresheild and I don't even see it unless I'm looking at it. Sitting in the cockpit of the -8, I'm comfortable that they will not bother me. Especially if I paint them.

Manual says DO NOT PAINT, but was told by a respected authority that a thin coat of flat black would not be a problem. Makes sense considering some put them under the cowl.

I could not completely get the 3" recommended distance from windscreen, but did get the recommended minimum spacing between them.

As you can see it's not flying yet, but I don't expect any problems. We shall see.
 
what we did.

WE put a constant card compass in the middle of the glair-shield, then put the puck up on the skin just to the left of the front Baggage. It work grate up there and is away from any heat or "EMF". There is very little drag on the tear-drop pucks anyway at that sight. We also have a location over the rear hat rack just as you see in the other above posts. That one is for the back up GPS to fall back on. Just what we did and it work quite well. Yours, R.E.A. III # 80888
 
Mine is located under the cowling so can't help with your specific question, but be aware that some GPS manufacturers require a minimum decibel loss (usually caused by the length of coax between the receiver and the antenna) in the coax. Mounting it on the glare shield will require you to engineer that into the installation.

Looks like all Garmin installations require some cable loss, 1.5db to 3db min, 7db max etc. So instead of running 20' of cable (and weight) why cant we use a $10 5-1500Mhz satellite splitter,
dumping one side into a 50ohm termination and the other to the GPS receiver? That puts the antenna on the glare shield as desired......(?)
 
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