GTN650 suddenly can't hold it's position

[BillL]

If there is a bad batch, Garmin does not make these, right? Isn't it Aeroantenna?

What are the serial numbers of the failed units. Mine might have been made at the same time. I would like to know.

[Mike S]

Originally Posted by krw5927

Sounds like yet another possible GA35 antenna failure. Do you have a friend nearby who would be kind enough to swap GPS antennas with you for a flight?

If you are in Reno--------hop over the hill to O61-----I have a NIB antenna you can put in for a test run.

[jthocker]

Originally Posted by Sig600

Anyone seen this before?

My GTN650 has started just randomly losing satellites, and dropping position. Usually pulling the breaker and cycling the power will get it back. Yesterday it took several minutes to acquire. The satellite status page will just be grey bars going up and down, every now and then one will turn green then go away. Then, like it's had some stroke of brilliance they'll all light up and turn blue and I'm off. Then sometime later my Skyview will announce GPS1 FAIL and we're at it again.

At first I thought there may be interference but the antenna is located right next to the skyview antenna and the dynon holds 9 satellites while the Garmin is struggling.

This is a new development in the last few flights. Pretty sad if this $10K piece of gear is failing at 100 hours.



Thoughts?

The latest revision in the GTN650 install manual (rev. L)
page 3-8
states: 12 inches between antennas is preferable and less than 9 inches WILL result in antenna degradation!

How about moving the beloved Skyview antenna and see how it all works?

[BillL]

Originally Posted by jthocker

The latest revision in the GTN650 install manual (rev. L)
page 3-8
states: 12 inches between antennas is preferable and less than 9 inches WILL result in antenna degradation!

How about moving the beloved Skyview antenna and see how it all works?

Thanks John, I'll be installing mine (G3X, GDL39R, and GTN 650) soon. I had planned under cowl, but now the geometry for that has changed. Most of us don't have an install manual. Is it available now?

[Sig600]

Originally Posted by jthocker

The latest revision in the GTN650 install manual (rev. L)
page 3-8
states: 12 inches between antennas is preferable and less than 9 inches WILL result in antenna degradation!

How about moving the beloved Skyview antenna and see how it all works?

That's what stein says... Still confused me that it would be just fine for 100 hours and the poof.

[avionicsr]

Originally Posted by Sig600

My antennas are under the cowl, never been washed let alone rained on. Swapping the antenna sounds like the next logical step. I have an email out to Garmin, I'll post what I hear back.

We've found that under the cowling is not the greatest location for GPS antennas. The heat tends to get to them and damage them fairly quickly. They were never designed to operate in that kind of thermal environment. Most of the heating takes place after shutdown. Let alone the issues of shading everything aft of the antenna close to the horizon. I would recommend mounting your replacement antena somewhere else.

[BillL]

Originally Posted by avionicsr

We've found that under the cowling is not the greatest location for GPS antennas. The heat tends to get to them and damage them fairly quickly. They were never designed to operate in that kind of thermal environment. Most of the heating takes place after shutdown. Let alone the issues of shading everything aft of the antenna close to the horizon. I would recommend mounting your replacement antena somewhere else.

So -what is the max allowed temp. Even the top of a fuse is pretty hot in Tuscon in the summer.

Here is a funny link - http://sarasotaavionics.com/avionics/at2300-326
It says the temp range is -500C to +700C. Wow, below absolute zero and hotter than the exhaust!

[avionicsr]

Originally Posted by BillL

So -what is the max allowed temp. Even the top of a fuse is pretty hot in Tuscon in the summer.

Here is a funny link - http://sarasotaavionics.com/avionics/at2300-326
It says the temp range is -500C to +700C. Wow, below absolute zero and hotter than the exhaust!

If I had to guess, I'd say there's a bit of a typo on that page. The Environmental Qualification Form for the GA35/GA36 says -55C to +85C. That's -67F to 185F

[BMW_X6M]

I had this problem ever since I installed the GTN650 about two years ago. I am not using it for IFR yet, and I have a Dynon Skyview working perfectly, so I had let it go until now. I was basically just out of warranty. I emailed support at Garmin, and they authorized a replacement to be sent out by my original vendor, Sarasota Avionics. Today I filled out a Sarasota Avionics RMA online request, and had an immediate RMA. I had good email support from both Garmin and Sarasota about my request for a replacement antenna. This makes me wonder if both know of problems with this antenna. My installation is under the cowling on a RV-9A. It would happen intermittently, sometimes only once per flight. At first I thought it was from the aircraft attitude, and the antenna shadowed by the firewall somewhat. But, it would also happen in level flight. The obvious issue was that one second I would have 10 or more satellites, and then the next second they would all be gone, and it would be slowly establishing contact with them again. This could also be due to a cable issue, with the power supply for the antenna going away. I checked my cables and as far as I could tell, they were good. I appreciate the support I received from Garmin and Sarasota Avionics on this one.

[BMW_X6M]

The problem I was having with losing satellites has been resolved by replacing the GPS antenna. I have been on several flights since changing the antenna and I have had no further issues.