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Bob Hoffman

Well Known Member
For those who have mounted their gps fwf under the cowl.How has it worked out for you ? Any problems that you know of like heat or vibration that may interfere with prorer operation ?? What about type of paint being a problem ?
I'd like to mount mine this way but checking those that have gone before me first.
Thanks
Bob
 
Have my GNS430 and XM Weather antennas under the cowling. Cowl is painted with metallic paint. I have no reception issues, everything is working fine.
 
430 antenna under the cowling, JetGlo paint, zero difficulties in four years and 1,000 hours....

Paul
 
The -8 in my hangar has two GPS and the XM antenna on a shelf on the firewall. Works fine, but sure makes it a pain to get your hands under there to get the cowl off or do any work. I'd much rather see them on the glareshield or aft fuselage under the bubble.
 
2 gps antennas and the XM antenna

No problems in 750 hours. Jetglo paint. I do lose the XM radio signal when I bank > 60 degrees away from south, but comes right back after leveling. Don't think this is because it is under the cowl though. :)
 
Thanks all for the reply.
Made my mount over the weekend worked out fine. HINT If you are planning to do the same and are thinking of mounting it on the Right side firewall top
remember that there is a cowling access door AND oil dip stick that may get in the way.Ask me how I know (and I didn't spot it one of my neighbors did).It is now mounted on the left side.
Bob
 
On the left side is an oil filter. If you have the 90 degree model, that would certainly preclude the gps shelf being on that side.
 
Bob Hoffman said:
.....I'd like to mount mine this way but checking those that have gone before me first......
Click to expand...
Bob,

It seems to me many of the responses are assuming you plan to install Garmin and in that case the antenna should work just fine mounted under the cowl. My firewall mounted 430 antenna has performed perfectly for several years but I contacted Garmin tech before I did do so just to be sure. I expect the same performance with the 496 antenna mounted similarly in the -8.

It is important to note that other GPS manufacturer's antennas may not be designed to tolerate the heat and vibration that exists under the cowl. If you are going to install a GPS other than Garmin, it may be prudent to contact the GPS manufacturer first.

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Rather than attach my antennas to the firewall, I made a 'shelf' out of .090" 2024T3 with aluminum angle added for rigidity. Attached to engine mount using adel clamps and spacers. Works great and think there's less vibration than mounting on the firewall. If anyone wants a picture I can post, but it might be a few days before I can.
 
Bob Hoffman said:
Yes , a picture (or two) would be appreciated.
Bob
Click to expand...

Here are 3 pictures of the installation. The smaller Garmin 696 antenna was 'glued' to the aluminum plate with high temp RTV. The installation has been working great and I have never had a loss of signal to either the 696 or the XM. I think mounting the antennas to the engine mount reduces the vibration the antennas are subjected to since the engine mount is rigid. I think a firewall mount might transmit more vibration since it is less rigid than the engine mount, although I have not done any testing to verify that theory. Another plus is that this method mounts the antennas up high and therefore signal 'shielding' from an adjacent structure is less likely. Hope this helps.

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flickroll,
Thanks for the pics , Nicely done, it never ceases to amaze me the skill and imagination and willingness to help that the RV community has.
Thank you all
 
flickroll,
Thanks for the pics , Nicely done, it never ceases to amaze me the skill and imagination and willingness to help that this RV community has.
Thank you all
Bob
 
Bob Hoffman said:
flickroll,
Thanks for the pics , Nicely done, it never ceases to amaze me the skill and imagination and willingness to help that this RV community has.
Thank you all
Bob
Click to expand...

You're welcome Bob. Another thing I considered when I decided to make the engine mount antenna shelf is that if/when I change avionics in the airplane and I have different and/or additional antennas to mount, I can whip up a new shelf pretty easily and mount it with the Adel clamp method. If the antennas are mounted on a shelf attached to the firewall (didn't like it there to begin with as I'd like to keep the number of holes in the firewall to a minimum), the new antenna mount will need to utilize the holes already in the firewall (which may not be the best solution for your new mount), or you drill new ones, adding even more holes to the firewall. YMMV
 
Here's a photo of the small garmin antenna shelf I fabricated. Bolted to the firewall near center, using 1" standoff tubes to keep it forward of the deck. No problems with reception or interference so far. Imron paint on cowl.

p1050197gpsantennashelf.jpg
 
Cutting GPS Antenna cable(Garmin)

you guys mounting the antennas under the cowl, is there any way to cut and splice these wires so as not to put a 5/8" hole in the firewall for the end of the Garmin wire?
Thanks
Al Grajek
 
algrajek said:
you guys mounting the antennas under the cowl, is there any way to cut and splice these wires so as not to put a 5/8" hole in the firewall for the end of the Garmin wire?
Click to expand...

Just another thought, since I used one for a cable. The one in the middle splits in half, which would allow the Garmin connector through, with no splice or end replacement. As I remember, the hole to mount this was somewhere around 7/8". But I'd check on the hole size first..

http://www.vansaircraft.com/cgi-bin...72145-492-705&browse=controls&product=one_eye

L.Adamson -- RV6A
 
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