Garmin G3X external antenna

This may be a question for Matt B or Stein-
I'm strongly considering a dual Garmin G3X setup, with a GDU375 and a GDU370, which will be connected to a Garmin GNS430W and TruTrak DFII VSGV. Since these GDU's will be panel mounted, what type and number of external antennas will I need for the GDU's? Currently, I have the 430W GPS antenna mounted inside the cockpit on top of the instrument panel.
I have seen where some recommend a separate antenna for each connection on the back of the GDU's, ie 2 GPS and 1 XM, versus a single antenna. Garmin also makes a combination GPS/XM antenna, so could this antenna be used? I think that I read where the GDU's can share GPS information, but does this mean a splitter in the GPS antenna line or sharing via a data link?
Thanks.

It's like this...

Each GDU display in a G3X system has its own internal GPS receiver. In a multiple-display system, you need to provide a GPS antenna for at least one of the displays, which will then communicate GPS data to the other displays that don't have antennas hooked up (i.e. there is no "splitter" involved). There's a configuration page you go to in order to tell the system "the PFD has a GPS antenna connected, the MFD does not", or whatever is appropriate to your installation.

If you spill your soda and knock out the GDU that has the GPS antenna, the remaining units will attempt to use GPS data from a 430/530, if you have one. This will be good enough to keep the little airplane symbol in the correct place on the map, but for various reasons you won't get quite the accuracy the system is designed for, so you'll see a caution message alerting you to this fact. If you decide you want more than one of your GDU displays to be hooked up to their own GPS antennas, that's fine too, you'll be adding extra redundancy.

As for antenna choices, it depends on whether you want internal antennas (mounted on the glareshield or hidden under a fiberglass fairing) or external antennas (mounted on the exterior skin of the aircraft). For internal antennas, you can use the GA26 and GA26XM, both of which are little black plastic things and are fairly inexpensive. If you want an exterior antenna, you can use any of the "white teardrop" GPS antennas called out in the install manual, and there is a dual-element antenna called the GA57X that gives you both GPS and XM.

As a specific example, my airplane has a three-display G3X system and dual 430Ws. There are three white bumps on the outside of my airplane: Two GA56W teardrop antennas (one for each 430W) and one GA 57X combo GPS/XM antenna, which feeds GPS to the pilot's PFD and XM to the MFD.

Hope that helps. By the way, be careful about mounting your 430W antenna on top of the glareshield. For reasons related to proper reception of WAAS signals, there is a minimum cable length called out in the install manual, and they really mean it!

mcb

Matt,

Where exactly did you externally install the three antennas? I will be doing an IFR panel upgrade to my flying 7A and will be configuring 2 G3X displays, with 1 Garmin 420W (no VOR) and 1 SL40 comm. I already have the GPS antenna installed on top of the fuselage midway between the vertical stab and the rail for the sliding canopy (distance from the radio for WAAS should be good). I would like to install the GA 57X EXTERNAL combo antenna and configure it the way you have described, where do you suggest installing the GA 57X combo antenna?
Thanx.

Victor

1000 words:



Not flying yet so I can't say how well this works, but it seems like it ought to. The G3X GPS gets a fix in my garage, anyway! I did verify that the sliding canopy will pass over the antennas.

mcb

Antenna cable length

Thanks Matt for the information. Looks like a single GPS/XM antenna will provide the redundency that I want.
About your comment concerning the antenna coax length for proper db gain, I had Stein make me one. Because of the short distance from the radio to the antenna, I have a coil of coax under my panel.
Thanks, Hobby

Matt,
Very nice antenna installation on your RV. Keeping in mind the minimum antenna coax length, did you ever consider mounting the antenna(s) ahead of the firewall inside the engine cowling? Yes, obsessive about drag, I know. Any downside to this location?
Thanks

terrye said:

Keeping in mind the minimum antenna coax length, did you ever consider mounting the antenna(s) ahead of the firewall inside the engine cowling? Yes, obsessive about drag, I know. Any downside to this location?

Click to expand...

I'm not sure what the official word is. I know people have put antennas there and had them work just fine. My personal opinion is that I don't like putting electronic devices in hot engine compartments, at least when they're designed to be mounted elsewhere. Now having said that, I might yet end up putting a little GA 26 antenna forward of the firewall to provide a secondary GPS source for my G3X MFD, depending on how I feel about it at the time. But I most likely won't put any of my primary antennas up there.

mcb

Antenna locations

Can anyone confirm that the antennas on top of Matts fulselage are okay being mounted so close together? Is there a distance requirement for mounting the antennas?


Thanx.

Victor

Antennas

I sell another style of gps antenna that you may want to consider. It is a thin film transparent design with the low noise amp in the cable. It has adhesive on one side and can be mounted under fiberglass or plexiglas. Here is a website with more details.

http://clear-nav.com/

I have one mounted under the engine cowl on my RV-4 and connected to a Garmin 496.