What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

placement of garmin antennas for dual G3X

R

rkochcyxh

Active Member
I'm hoping someone has the G3X and the Garmin antennas for them. I'm installing two G3X's, one has weather and XM. The question is, where to mount the antennas. One is the white rectangle and the other is the white teardrop. I'm building a 9a tip-up. right now I'm thinking, just behind the plex glass over the baggage area. One beside the other. Would really like to know what is working for others. Thanks
Russel Koch
RV9A
 
The Garmin folks that I have talked with cautioned against putting the 430W antenna next to ANY other antenna because it could block it's view in that direction near the horizon. I ended up putting the 430W antenna by itself on the turtle deck, and instead of the big dual antenna, I installed two tiny GPS antennas and an even smaller XM antenna on the glare shield (all on our -3 project). That gives a GPS antenna for each G3X display, and a single XM (for the single receiver).

Paul
 
I've pondered this too...

I have the same dual G3X set-up in my 7, but I haven't put the antennas in yet. When I asked Stein's people about this, they told me that all of these antennas would tolerate the heat under the cowling, so I'm kind of leaning toward that. I've seen several others like this and they work well. Well, as long as you put the antenna where it's not "shadowed" by the firewall, another antenna or any other metal obstruction. You can get creative mounting to the engine mount or the firewall and still have the necessary separation.

The same would apply if you're putting it in the baggage area. Seems to me that I saw pics of somebody that did what you're wanting to do. They fabricated a small "shelf" just behind the roll bar on which to mount the antenna. As I recall, they put one antenna on each side of the fore/aft cross member. But you might get some shadowing from the roll bar or the fore/aft member. You'll also have to look at what the allowable antenna cable length is, but I'm guessing that won't be an issue (stress the guessing part).

If you haven't tried already, I believe there are some other threads that you may be able to search through. There are a LOT of opinions on this.:rolleyes:
 
Placed Outside

If the antennas are placed on the top of the fuselage just behind the plexi glass, would that not give me better reception than on the glaresheild under the plexiglass?. But at what cost to speed? We are building an airplane that is fast, flush rivets,etc, and then we stick on external steps, and whip antennas, elt antennas and more.
Thanks
Russel Koch
 
rkochcyxh said:
If the antennas are placed on the top of the fuselage just behind the plexi glass, would that not give me better reception than on the glaresheild under the plexiglass?. But at what cost to speed? We are building an airplane that is fast, flush rivets,etc, and then we stick on external steps, and whip antennas, elt antennas and more.
Thanks
Russel Koch
Click to expand...

The GNS 430W antenna is shaped the way it is to create a pretty small amount of drag. I changed my 430 to a 430W in the -8 a few weeks ago, and found that the "W" antenna is MUCH more sensitive to losing lock due to shadowing (aerobatic tests) than the old system. If you have spent the money to go with a WAAS GPS, it pays to make sure it has a good view of the sky.

All the little antennas? They seem to do fine inside my office, with NO view of the world (except a little window....).

Paul
 
The issue I had with the 430W was that my original location was on top of the glare shield. I later learned that RF from the EFIS system was knocking out the 430 reception. I have learned that the 430W antenna must be at least 18" from anything producing RF. Also another antenna lesson was that the standard monopole transponder antenna will not work withe the GTX330/430W traffic monitoring and requires a CI-105.

Pat
 
My perspective:

I have a G430W, and a G696 w/XM. All 3 antennas (430, 696, XM) are mounted under the cowl and perform extremely well. The G430W has never lost a lock unless I'm doing acro. When it loses a lock during acro it quickly recovers when I return to non acro flying. When I am flying acro I really don't care that the 430 has lost its lock because I know where I am and I am not enroute anywhere. When I am enroute the 430 has always worked as designed. So for me, the 430 losing a lock during acro is a small penalty for the clean installation that is gained by mounting the antennas under the cowl. YMMV.
 
For what it's worth, there are different antennas available for the G3X displays (GA26C for GPS and GA26XM for XM) that are smaller and designed to be mounted inside the airplane or under a fiberglass panel:

ga26c.jpg


I wouldn't recommend putting these in the hot engine compartment, but you could put them on the glareshield if you wanted to.

The TSO GPS navigators (430W etc) obviously have to use the big white antennas and nothing else.

More information in this thread: http://www.vansairforce.com/community/showthread.php?t=61173

mcb
 
Last edited:
other compatible Garmin xm antennae

Will other xm antennae work with the G3X inside the cabin like those from Garmin that aren't specifically listed in the G3X installation manual?

Thanks,

Mike
 
alcladrv said:
Will other xm antennae work with the G3X inside the cabin like those from Garmin that aren't specifically listed in the G3X installation manual?
Click to expand...

The GA55, GA57X, and GX26XM will all work as the XM antenna for the GDU 375.

mcb
 
Pat Stewart said:
The issue I had with the 430W was that my original location was on top of the glare shield. I later learned that RF from the EFIS system was knocking out the 430 reception. I have learned that the 430W antenna must be at least 18" from anything producing RF. Also another antenna lesson was that the standard monopole transponder antenna will not work withe the GTX330/430W traffic monitoring and requires a CI-105.

Pat
Click to expand...

I have:
430W antenna on the glare shield above 2 EFIS and radio stack, no problems. Also 3 other gps/xm antennas on glare shield.
Standard monopole transponder (TED) with GTX330/430W, no problems.

3 years/300hrs. YMMV
 
alcladrv said:
Will the GXM 30 or GXM 40 work as well?
Click to expand...

No, the GXM30/40 are combination receiver-antenna devices... the XM receiver is inside the "hockey puck". The GDU 375 MFD already contains its own internal XM receiver, so all it needs is an antenna. (and in fact there's no place to plug in a GXM30/40)

mcb
 
I took the cheap way out and used the GA25 BNC antenna for my GDU 370. My GPSMap 696 uses the same antenna with a different connector. XM is on the 696 so it uses the standard one. For the time being all three antennas just sit on the glare shield.

A0001.jpg
 
You must log in or register to reply here.
Back
Top