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Gps signal loss


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Hey guys, 

flying up to Ohio today, 30 minutes into the flight, all gps signals lost on all devices.  Independently ...   iPhones, iPads included.  It was like gps signal was completely jammed on my airframe for the duration of the flight all the way to the ground 1.5 hours later.  While I was flying VORs, I tried cycling power ...  nothing.   

After landing, I shut down and tried turning the gtn back on, but nothing within about a minute, so I just turned it all back off and tied down.   I pulled the aera660 out on the ramp and was able to get signal.  And iPad came back to life as well.

Is it possible for an airframe to somehow become a ferrite choke and block gps reception?   Doesn’t make sense even if that’s the case, as the antenna is external.  No other planes in the area had any problems.  

Any ideas?

the only recent maintenance changes were a new Concorde battery, but I had flown twice before this flight without problem.   The only think first on this flight was a new navdata update for the gtn.

thanks

craig

Edited by Browncbr1
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Often...

Something in the plane is generating excess noise that easily can block GPS signals...

I had a a Narco nav/com that was good at that... The act of tuning certain Frequencies killed off my portable GPS...
 

Tune a different frequency, gps came back...

One known issue, but others can be as simple...

If it repeats on the next flight, start narrowing things down...

Best regards,

-a-

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Craig,

The Garmin 430/530 antennas have a failure mode where the failing antenna blocks GPS on the good system. I have experienced this failure mode. Perhaps this same problem exists in the GTNs.

Additionally, the SPOT GPS trackers have jammed other GPS receivers in the aircraft.

For background, GPS operates with negative signal to noise ratio -- meaning GPS receivers are dealing with VERY weak signals that are easy to jam. Check for other potential signal sources in the aircraft.

Cheers,

David

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Just now, carusoam said:

Often...

Something in the plane is generating excess noise that easily can block GPS signals...

I had a a Narco nav/com that was good at that... The act of tuning certain Frequencies killed off my portable GPS...
 

Tune a different frequency, gps came back...

One known issue, but others can be as simple...

If it repeats on the next flight, start narrowing things down...

Best regards,

-a-

Thanks for the quick reply.  I have flown this route many times, so I doubt it would be any of the com frequencies, plus I kept changing along the way.   I don’t have a dme, as I know those frequencies can interfere without using a switch or filter, or whatever it’s called.    I’ll try turning off my kx155 and other stuff to see if that helps.  Thanks for the idea. 

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When the G530s and 430s were new...

Many people found out that their existing antenna locations were no longer a good place to mount the new GPS antennas...

They were too close together... and one GPS would kill the other... leaving both dead...

Took a lot of days waiting to get that all figured out... lots of nervous new gps owners...

Its amazing how much noise a receiver can emit... the old analog stuff is much worse than newer digital stuff...

Best regards,

-a-

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Just now, carusoam said:

When the G530s and 430s were new...

Many people found out that their existing antenna locations were no longer a good place to mount the new GPS antennas...

They were too close together... and one GPS would kill the other... leaving both dead...

Took a lot of days waiting to get that all figured out... lots of nervous new gps owners...

Best regards,

-a-

-a-,

That is an interesting, but irrelevant, tidbit. Perhaps "I experienced this failure mode" should have been a clue to you. The failure occurred in a seven year old installation -- resolved by replacement of the failing antenna.

Do you have direct knowledge of an engineering change by Garmin that eliminates this failure mode? If so, when was it issued?

David

 

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8 minutes ago, David Medders said:

-a-,

That is an interesting, but irrelevant, tidbit. Perhaps "I experienced this failure mode" should have been a clue to you. The failure occurred in a seven year old installation -- resolved by replacement of the failing antenna.

Do you have direct knowledge of an engineering change by Garmin that eliminates this failure mode? If so, when was it issued?

David

 


David,

This (Tidbit that I’m writing about) was an install issue...

Where MSer’s installers we’re not following the guidance for antenna placement...

They were following the existing holes of other equipment that was being removed...

The challenge was... too few people had Deep enough experience installing GPS antennas...

The discussions must have been in the early days of MS... the records might still exist...

 

I gave it as an example of how sensitive GPS(s) can be to each other... or other equipment can be to GPS(s)

I also have a challenge with writing.  Not always getting my point accross... :)

My understanding isn’t so good either... some clues go right over my head...
 

Best regards,

-a-

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Just now, carusoam said:


David,

It was an install issue...

Where MSer’s installers we’re not following the guidance for antenna placement...

They were following the existing holes of other equipment that was being removed...

The challenge was... too few people had Deep enough experience installing GPS antennas...

The discussions must have been in the early days of MS... the records might still exist...
 

Best regards,

-a-

-a-,

Interesting, but still irrelevant to my post.

In the absence of direct knowledge of an engineering change by Garmin, we must assume the failure mode I experienced still exists.

David

 

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10 minutes ago, David Medders said:

-a-,

Interesting, but still irrelevant to my post.

In the absence of direct knowledge of an engineering change by Garmin, we must assume the failure mode I experienced still exists.

David

 


oddly enough,

I was trying to fill in details to help the OP (Craig) out...
I’ll try and see if I know anything about what you are discussing...

 

keep in mind, I’m only a PP, not an RF engineer... :)

Best regards,

-a-

There are a few mentions of Garmin antenna failures ruining reception for everything else...

it is probably faster to find your answer by talking with Trek Lawler at Garmin directly...

https://mooneyspace.com/search/?q=Garmin gps antenna failure&updated_after=any&sortby=relevancy&search_and_or=and

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Thanks for all the ideas guys.  This install is 3 years old and was done from scratch by a proper shop.  Never had any outage before.  

Im going to try turning on handheld gps units prior to powering the gtn on to see if the gtn antenna is causing some kind of rf interference.  

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10 hours ago, Browncbr1 said:

Hey guys, 

flying up to Ohio today, 30 minutes into the flight, all gps signals lost on all devices.  Independently ...   iPhones, iPads included.  It was like gps signal was completely jammed on my airframe for the duration of the flight all the way to the ground 1.5 hours later.  While I was flying VORs, I tried cycling power ...  nothing.   

 

Sort of funny, I was bored at work yesterday and was looking at Mooneys on https://www.adsbexchange.com/ and watching your flight (along with a bunch of others across the US). You were moving along around 200 mph. 

I think trying to turn things off individually to isolate it is the best idea. 

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8 minutes ago, JimB said:

Sort of funny, I was bored at work yesterday and was looking at Mooneys on https://www.adsbexchange.com/ and watching your flight (along with a bunch of others across the US). You were moving along around 200 mph. 

I think trying to turn things off individually to isolate it is the best idea. 

Oh wow, yes, if you go back and look at the flightaware data, on HTS approach before switching to Indy center, you can see the track go really jaggedly.   The bearing goes back and forth 90 degrees each data point from there throughout.  Really weird.  It was smooth and decent winds..  

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25 minutes ago, Browncbr1 said:

Oh wow, yes, if you go back and look at the flightaware data, on HTS approach before switching to Indy center, you can see the track go really jaggedly.   The bearing goes back and forth 90 degrees each data point from there throughout.  Really weird.  It was smooth and decent winds..  

Interestingly, the ADS-B data is based on GPS location. 

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I found this on VAF..   seems to be well documented.    Seems that the antenna can inadvertently ground and the antenna becomes a transmitter rather than receiver, thus jamming everything.   This is also from early 2018, which is exactly when my unit was installed.  

http://www.vansairforce.com/community/archive/index.php?t-158524.html

 

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This problem has been around for quite sometime.  There should probably be an AD because of the possible loss of all GPS reception.

It was discussed in 2014 on Mooneyspace.

https://mooneyspace.com/topic/11114-garmin-430w-gps-antenna-problem/

 

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David,

May I ask why you felt the need to respond to -a- in the manner you did on his response to Craig after Craig replied to -a- on his post about his experience with a similar failure due to a radio antenna blocking his GPS signal? I do not see where he addressed his comment to you, and, like you, he was sharing a failure mode he experienced in flight. From my perspective, I did not see -a- devaluing your contribution in the least but rather sharing his different experience, which is something many of us have. It left me confused as to the reason behind your response.

Looking at your signature line, it is apparent you likely have had experience and situations many of us here will never encounter. I believe many of us are interested to hear how those of you flying for a living handled them in the hope we can learn from you. I hope you continue to share them with us.

Regards,

John

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I just wanted to provide a little update here.  I went out to the field today to look over things.  First, I inspected the ga35 antenna very closely with a magnifying glass.   It looks perfect and sealant is perfect.   Then, I looked at the bnc connectors to ensure everything was good and not touching anything else.  So I pulled the gtn breaker and verified I had gps on the iPad, then turned avionics master on..   neither the gdl, nor the aera could get gps signal.    iPad gps sitting on my wingwalk was ok.  I stuck my finger under the glare shield to undock the aera and then the satellite signal page lit up.  I then thought, ok, something is going on under the glare shield...  I pull it up a little to reveal the remote external gps antenna that is hooked up to the GDL39.  Its been there for years sitting on top of the panel subframe.   The remote antenna has a plastic film coating on the metal on the bottom side of it.   Some of the film was worn away from the edge and it seems it was grounding to my panel, which was jamming signals.  I moved the antenna to sit on the fiberglass glareshield and I could not replicate the signal jamming issue.   

Duuuuuuuuuhhhh

Edited by Browncbr1
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4 hours ago, carusoam said:

Great follow up, Mr. Brown!

Any issues finding a replacement for the worn insulation?
 

is that an easy fix? Or is it a new antenna requirement?

See Alan if you need a new antenna...

Best regards,

-a-

I just moved it to sit on top of the fiberglass...  I think some electrical tape around the bottom of the gps puck would help.   Or get a new one that has plastic all around the puck.  This particular antenna is a cheap one I had on the shelf from an old stratux build.   I guess I had that one coming.

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