Which WAAS Antenna on G3X

Hi Experts,

I'm hoping to get a clear answer about which antenna is appropriate or best choice for WAAS GPS backup, if the GTN dies.

I've seen where some are using the remote suction cup antenna but that seems to keep it too close to the COM stack for best reception.

The install manual is not clear about specifically which to use as a permanent mount antenna.

Help would be appreciated.

A GPS antenna is required for G3X operation, it doesn't share GPS data with the GTN. If you want a permanent mount I think the GA56 would be the appropriate unit. Section 23 of the install manual give you all the info on GPS antennas.

sorry, not clear

Walt said:

A GPS antenna is required for G3X operation, it doesn't share GPS data with the GTN. If you want a permanent mount I think the GA56 would be the appropriate unit. Section 23 of the install manual give you all the info on GPS antennas.

Click to expand...

Hi Walt,

I appreciate the response but maybe there differences between versions of the install manual. Mine is dated March 2018. It doesn't indicate the GA56 as a WAAS antenna. But it does show the GA35 as WAAS. To make things more confusing it says the GA35 is only for the GPS20A. That is not correct as it's used on the GTN625 and 650/750. Further the GA35 is TNC so in theory better for the higher frequencies, and less expensive than the GA56.

So, is there a reason why GA56 instead of 35 and does your doc say it's WAAS? Could you point me to that doc?

Thanks.

According to the GA35 specs, it doesn't meet the G3X's GPS antenna requirements. My guess is would probably work, but better just to get one of the recommended antennas listed in the G3X install manual.

FWIW, I have a 2-screen non-touch G3X system. My PFD is connected to an externally mounted GA57 GPS/XM antenna and the MFD is connected to a GA26 that's on my glareshield (right up against the windscreen and directly in front of the pilot's seat. I've tested the 26 in that location and I haven't noted any reception issues.

still want WAAS

Auburntsts said:

According to the GA35 specs, it doesn't meet the G3X's GPS antenna requirements. My guess is would probably work, but better just to get one of the recommended antennas listed in the G3X install manual.

FWIW, I have a 2-screen non-touch G3X system. My PFD is connected to an externally mounted GA57 GPS/XM antenna and the MFD is connected to a GA26 that's on my glareshield (right up against the windscreen and directly in front of the pilot's seat. I've tested the 26 in that location and I haven't noted any reception issues.

Click to expand...

Got it. Appreciated. The major diff appears to be the GA35 could draw more milliamps.
And I would like to go by the recommendations except the GA57 is not listed as a WAAS antenna. Even AC Spruce shows it as non-WAAS.

Cheers.

1bigdog said:

Hi Experts,

I'm hoping to get a clear answer about which antenna is appropriate or best choice for WAAS GPS backup, if the GTN dies.

I've seen where some are using the remote suction cup antenna but that seems to keep it too close to the COM stack for best reception.

The install manual is not clear about specifically which to use as a permanent mount antenna.

Help would be appreciated.

Click to expand...

Hello Michael,

It is really simple. Per page 23-2, use the GA 26C antenna if you want a low cost antenna mounted inside on the glare shield, or use a GA 56 (GPS) or GA 57X (GPS/SXM) antenna if you want to mount an antenna on the external surface of the aircraft.

Do not, under any circumstance, connect a GA 35, GA 36, or GA 37 antenna to the WAAS GPS receiver connection on a GDU 37X or GDU 4XX display.

Don't get hung up on the WAAS/non-WAAS names used on some antennas. All of the G3X and G3X Touch displays have high performance WAAS GPS receivers built into them, and what is important is using an antenna that works well with this receiver and doesn't draw too much power.

Even though the GA 56 antenna is not suitable for the WAAS GNS/GTN receivers, it is a good electrical match and works great for the GDU 37X/GDU 4XX WAAS GPS receivers.

The GPS 20A uses the same WAAS GPS receiver as the GTN, so naturally it uses the same GA 35/36/37 antenna.

Thanks,
Steve

Thanks for the clarifications and input

Thanks all for the input and clarifications.