430W losing satellites

[ragedracer1977]

This first happened to me a couple months ago after I installed a remote GPS antenna for the stratus.  I removed it and the problem seemed to go away.  But... it’s back.  Flying to San Diego over the weekend, it happened 5 times enroute to KSAN, and once coming back.  Each outage was maybe 1-3 minutes and if I scrolled to the satellite page, it showed zero satellites, but then you could watch them reacquire.  Got old reporting loss to ATC and then back on again.  My stratus (on the glareshield) never lost signal.  

Time for a new GA35 antenna, or should I be looking elsewhere??

[ArtVandelay]

Easy fix would be to check antenna connections, while on the ramp wiggle the coax and see if you can recreate, if GPS antenna underneath the headliner it might be difficult to check coax/antenna connection. Hopefully it’s just a bad connection on the back of the GPS, a little electronic cleaner or new connector and you’ll be good to go.

[Jerry 5TJ]

You might try using a gps antenna from a portable device as a test to isolate the problem.  Any amplified gps antenna unit that is powered (via the coax cable) with 3 to 5 volts will serve. 

[Yetti]

Think noisy power supply for the Straus

[LANCECASPER]

2 minutes ago, Yetti said:

Think noisy power supply for the Straus

Or cheap usb charger in the cigarette lighter.

[ragedracer1977]

1 hour ago, LANCECASPER said:

Or cheap usb charger in the cigarette lighter.

Nope.  Plugged in or not had no effect. 

1 hour ago, Yetti said:

Think noisy power supply for the Straus

Even if I powered down the Stratus (it was running on battery) the signal didn't change.

5 hours ago, Jerry 5TJ said:

You might try using a gps antenna from a portable device as a test to isolate the problem.  Any amplified gps antenna unit that is powered (via the coax cable) with 3 to 5 volts will serve. 

Can you elaborate? I'm not sure I get what you mean.

[N201MKTurbo]

The problem is either interference or attenuation. 

GPS signals are very weak it doesn't take much interference to significantly reduce the SNR of the received signal. The interference may not be at the fundamental frequency of the signal. The Stratus may be radiating some signal that is getting into your Garmin antenna. 

Interference can also be sent up the Garmin's own antenna coax from noise on its power supply.

If you put two antennas of the same frequency near each other, they can couple to each other and degrade the performance of both antennas. This usually only happens when within a few wavelengths. The wavelength of GPS signals is about a foot.

[N201MKTurbo]

13 hours ago, ragedracer1977 said:

This first happened to me a couple months ago after I installed a remote GPS antenna for the stratus.  I removed it and the problem seemed to go away.  But... it’s back.  Flying to San Diego over the weekend, it happened 5 times enroute to KSAN, and once coming back.  Each outage was maybe 1-3 minutes and if I scrolled to the satellite page, it showed zero satellites, but then you could watch them reacquire.  Got old reporting loss to ATC and then back on again.  My stratus (on the glareshield) never lost signal.  

Time for a new GA35 antenna, or should I be looking elsewhere??

Consider the continuous GPS interference NOTAMS along that route. I think the government is doing strange things especially in the vicinity of the Yuma Proving Grounds.

[Marauder]

Consider the continuous GPS interference NOTAMS along that route. I think the government is doing strange things especially in the vicinity of the Yuma Proving Grounds.

Are you getting a LOI message or just complete loss of the sats?


Sent from my iPhone using Tapatalk Pro

[N201MKTurbo]

15 minutes ago, Marauder said:

 

Are you getting a LOI message or just complete loss of the sats?


Sent from my iPhone using Tapatalk Pro

 

You should ask Brice. 

I did see this on my trip to LA last week on my Avidyne. It was within 50 miles of the proving grounds. I was flying the airways, you kind of have to through there because of the restricted zones, and just switched to VLOC. It came back on in about three minutes.

[ragedracer1977]

40 minutes ago, Marauder said:

 

Are you getting a LOI message or just complete loss of the sats?


Sent from my iPhone using Tapatalk Pro

 

Both. LOI message "using dead reckoning".  When I switch to the satellite page, it shows zero.

[ragedracer1977]

22 minutes ago, N201MKTurbo said:

You should ask Brice. 

I did see this on my trip to LA last week on my Avidyne. It was within 50 miles of the proving grounds. I was flying the airways, you kind of have to through there because of the restricted zones, and just switched to VLOC. It came back on in about three minutes.

According to ATC, I was the only one reporting an outage, but... I was pretty much by my lonesome at low altitude.  Everyone else was jets or not talking. 

It is interesting to note, though, it only happened around the restricted areas.

Edited September 3, 2018 by ragedracer1977

[ragedracer1977]

2 hours ago, N201MKTurbo said:

The problem is either interference or attenuation. 

GPS signals are very weak it doesn't take much interference to significantly reduce the SNR of the received signal. The interference may not be at the fundamental frequency of the signal. The Stratus may be radiating some signal that is getting into your Garmin antenna. 

Interference can also be sent up the Garmin's own antenna coax from noise on its power supply.

If you put two antennas of the same frequency near each other, they can couple to each other and degrade the performance of both antennas. This usually only happens when within a few wavelengths. The wavelength of GPS signals is about a foot.

The GA35 is on top of the airframe, behind the baggage compartment.  The Stratus was on the glare shield, but it happened even with the Stratus powered off and not plugged in

 

Just a thought.. could a cell phone gps interfere? Come to think of it (that I can recall) it's only happened when the kids are in the back seat.

Edited September 3, 2018 by ragedracer1977

[N201MKTurbo]

1 minute ago, ragedracer1977 said:

The GA35 is on top of the airframe, behind the baggage compartment.  The Stratus was on the glare shield, but it happened even with the Stratus powered off and not plugged in

That shouldn't be a problem. You should ask Eric he is the radio expert.

[Yetti]

2 hours ago, ragedracer1977 said:

Just a thought.. could a cell phone gps interfere? Come to think of it (that I can recall) it's only happened when the kids are in the back seat.

Should not, but it could.  When your cell phone loses a tower it switches to higher power to try and find a tower.   Might try the airplane mode for the kids.   Even a noisy VHF radio could be an issue.

[Jerry 5TJ]

If you suspect interference from your comm radios or the ELT you could try a notch filter in the antenna line of the offending radio. 

GPS Notch Filter

If you’re an RF-minded CB you can make your own: the GPS filter is just a quarter-wave open stub transmission line.  

[ragedracer1977]

48 minutes ago, Jerry 5TJ said:

If you suspect interference from your comm radios or the ELT you could try a notch filter in the antenna line of the offending radio. 

GPS Notch Filter

If you’re an RF-minded CB you can make your own: the GPS filter is just a quarter-wave open stub transmission line.  

The ELT is a Narco ELT10. As far I understand it doesn't transmit anything.  

It sounds like I'm going to have to do some experimentation to figure it out.  

[Andy95W]

Brice- a couple years ago, someone posted here about a similar problem as yours.  The ELT antenna was setting up a weird harmonic that was throwing off the GPS reception- even without the ELT transmitting.  A notch filter fixed his problem.

[jma201]

The same thing is happening to me.  The google machine indicates it is a known issue with some GA35 antennas.  I found this on the Vans site:

http://www.vansairforce.com/community/showthread.php?t=158524

 

 

[bill98]

I had the same issue mid august! It went out on me. Be sure not to get too distracted trying to trouble shoot when satellite goes out!

[nfonville]

I had this same issue.  No troubleshooting just replaced the GA35. There is a known issue with some early releases of this antenna.  My symptoms were exactly the same on my G530W.

[ragedracer1977]

On 9/3/2018 at 3:30 PM, Jerry 5TJ said:

If you suspect interference from your comm radios or the ELT you could try a notch filter in the antenna line of the offending radio. 

GPS Notch Filter

If you’re an RF-minded CB you can make your own: the GPS filter is just a quarter-wave open stub transmission line.  

As it turns out... It looks like it's my Narco NCS-812 navcom.  I was flying up to KSOW this afternoon.  Everything was good.  I switched to get the ATIS at KPAN (119.325). As I was listening, I noticed that my Stratus lost GPS.  Then my 430.  I thought, ok here we go again. But I started thinking.  I turned the radio off. Instantly got GPS back.  Then I started experimenting.  I turned the radio back on.  After a few seconds, I lost GPS.  I flipped the frequency back to 126.5 (DVT ATIS), GPS instantly back.  Kept playing and figured out that if the Narco is tuned to between 119.275 and 119.675, I lose GPS.  

Weird!

[Jerry 5TJ]

Glad you’ve found a reproduceable source of your GPS outages.   Intermittent problems of unknown origin can be hell to troubleshoot.  

Assuming the interference comes via the comm antenna, here are  my suggestions on fixing the issue —from simple to harder:  

• Try putting that notch filter in the comm coaxial line 
• replace the comm coaxial cable with a new run of RG-400, routing the new cable away from GPS antenna cable as much as possible 
• move the comm antenna to the belly.  
• Replace the Narco 

 

[ragedracer1977]

Well... Hmm.  On the return flight this morning, I could not reproduce.  I wonder if it's also maybe heat related?  It was about 80 OAT yesterday and 50 OAT this morning

[Andy95W]

8 hours ago, Jerry 5TJ said:

Glad you’ve found a reproduceable source of your GPS outages.   Intermittent problems of unknown origin can be hell to troubleshoot.  

Assuming the interference comes via the comm antenna, here are  my suggestions on fixing the issue —from simple to harder:  

• Try putting that notch filter in the comm coaxial line 
• replace the comm coaxial cable with a new run of RG-400, routing the new cable away from GPS antenna cable as much as possible 
• move the comm antenna to the belly.  
• Replace the Narco 

 

+1. Great advice.