How much do you trust your Garmin 530?

[Joe Larussa]

On 12/9/2017 at 10:52 AM, Piloto said:

Verify your GNS 530W has the latest software. Latest revision address some of these issues.

https://www.garmin.com/en-US/aviationalerts/service-bulletin-1317-gps-400wgnc-420wgns-430wgps-500wgns-530w-series-units-software-upgrade-to-main/

José

 

Looks like I'm running 5.3

[Joe Larussa]

9 hours ago, Piloto said:

Did the problem started after the upgrade? It may be related to the 530 programming.

Yeah it did.

[Piloto]

Just now, Joe Larussa said:

Yeah it did.

Try reprograming the 530 again. The problem could be related to a minor glitch during programing the unit or software download. Contact Garmin, they may have an unknown bug on 5.3.

José 

[Joe Larussa]

Just now, Piloto said:

Try reprograming the 530 again. The problem could be related to a minor glitch during programing the unit or software download. Contact Garmin, they may have an unknown bug on 5.3.

José 

I sent Garmin the video and waiting for a response. My avionics guy says he has one on the bench that's doing the same thing.

[larryb]

When you lost satellites, were you transmitting with the GNS radio or a KX-155? KX-155's can interfere with GPS. The installer is supposed to check them.

The certification test requires that the GPS stay active when the microphone  is keyed on the following frequencies. These frequencies have harmonics in the GPS range and if the radio is not well shielded they can leak out and interfere with the GPS signal. The GPS should be able to withstand 30 seconds of TX on each of these frequencies.
 
 121.150
 121.175
 121.200
 131.250
 131.275
 131.300

[Joe Larussa]

12 minutes ago, larryb said:

When you lost satellites, were you transmitting with the GNS radio or a KX-155? KX-155's can interfere with GPS. The installer is supposed to check them.

The certification test requires that the GPS stay active when the microphone  is keyed on the following frequencies. These frequencies have harmonics in the GPS range and if the radio is not well shielded they can leak out and interfere with the GPS signal. The GPS should be able to withstand 30 seconds of TX on each of these frequencies.
 
 121.150
 121.175
 121.200
 131.250
 131.275
 131.300

I was using the Garmin not the KX155.

[bradp]

Oh - did you upgrade the gps firmware at the same time? Both sets instructions - 530 and gps firmware need to be followed to the letter.  

Anecdote- My photocell Auto dim response curve got seriously messed up after we updated the gdl software through the GNS so these things do contain bugs.  

[Joe Larussa]

Garmins reply to the video

 

Thank You for contacting Garmin International. From your video it appears that you have WAAS RF COM interference. Please contact your Garmin dealer. They will need to troubleshoot the cause of the interference at the aircraft. This could be caused by multiple systems in the aircraft that are transmitting near the GPS signal range. Items transmitting near that range may have a harmonic that ends up at the same frequency of the WAAS GPS signal of 1575.42 MHZ. This will cause the GPS signal to drop out. The GNS 530W will not cause the problem. 

 

Best Regards,

[takair]

Regarding the previous discussion ref. the ELT, it can be a real issue.  A com transmission can be picked up by the ELT and the ELT ends up creating a harmonic internally and reradiating it to interfere with the GPS.  There were some notifications years back.  The older ELTs in particular were not very sophisticated.  As someone suggested, do a flight without it.  Get flight following to be safe.  It is odd that it started after the upgrade.  Depending on the installation, someone may have used the ground feature on the back of the rack.  I have found that this easily corrodes and degrades the grounds, which may in turn eliminate some of the shielding to the 530.  I have since stopped using that as a ground and run all grounds and shields to a more substantial ground.  This one will drive you crazy, because it will ring out.  I have also seen a second GPS antenna fail and cause emissions that take out the good side, in this case, both GPS’s tend to fail simultaneously.

I would concentrate on isolation. Pay particular attention to keying the comms and other events that may have occurred even some seconds before the signal loss....it may even occur prior to the FAF, because the LPV requires some stability and may be flagging loss of integrity, or it predicting a loss of integrity.  You may also want to turn off any non essential equipment as part of the process, particularly anything with an antenna.  Hang in there, you will find it.  I suspect you can troubleshoot this without doing LPV approaches, figure out what is causing the satellite bars to drop.  Sorry if this has all been discussed, skimmed through the thread.

[Piloto]

20 hours ago, Joe Larussa said:

Garmins reply to the video

 

Thank You for contacting Garmin International. From your video it appears that you have WAAS RF COM interference. Please contact your Garmin dealer. They will need to troubleshoot the cause of the interference at the aircraft. This could be caused by multiple systems in the aircraft that are transmitting near the GPS signal range. Items transmitting near that range may have a harmonic that ends up at the same frequency of the WAAS GPS signal of 1575.42 MHZ. This will cause the GPS signal to drop out. The GNS 530W will not cause the problem. 

 

Best Regards,

How the above explains the 530 at the shop having the same symptoms but on the bench.

José

[Joe Larussa]

On 12/13/2017 at 8:06 AM, Piloto said:

How the above explains the 530 at the shop having the same symptoms but on the bench.

José

Shot the same approach last night with mixed results. First approach turned everything off. Ipad, gdl 39 and cell phone.

Lost LPV but way before final but came back quickly. Then I turned everything on and no problems at all. Somthing I thought

of is about maybe 25 miles from the airport there are TV towers that are about 2300 feet in the air. Thoughts?

[Jerry 5TJ]

External RF interference is possible.  So is deliberate jamming.   If your coverage loss is in same geographical area each time that’s a clue. 

If so, a suggestion:  File a  NASA ASRS form and describe the GPS interruption.  

I frequently flew a route years ago (LHS V459 SLI) and noticed that as I flew south bound at 9,000 I’d get an outage in enroute coverage just as I passed a ridge topped with numerous radio towers. On the return trip at 10,000 it never happened. After about 5 trips I had the area of disruption pretty well documented.  

I put full details in an ASRS form and submitted it.  I got a quick reply “we will definitely look into this!” written on the receipt.  

On your side the same remedies as already posted:  Make sure RF connectors, coax cable, antenna are in best possible condition.  

[takair]

6 hours ago, Joe Larussa said:

Shot the same approach last night with mixed results. First approach turned everything off. Ipad, gdl 39 and cell phone.

Lost LPV but way before final but came back quickly. Then I turned everything on and no problems at all. Somthing I thought

of is about maybe 25 miles from the airport there are TV towers that are about 2300 feet in the air. Thoughts?

So, did You have any transmissions on the approach?  Would you mind sharing the approach and waypoints?  Maybe something will jump out to someone.

[bradp]

Notch filter?  I know that the comant fancy antennas have a built in notch filter to address the proximity of the two antennas. 

 

[Joe Larussa]

On 12/14/2017 at 3:18 PM, takair said:

So, did You have any transmissions on the approach?  Would you mind sharing the approach and waypoints?  Maybe something will jump out to someone.

Here is the approach plate. Was talking to NorCal until about 4 miles before Sebae.

[takair]

On 12/14/2017 at 12:09 PM, Joe Larussa said:

Joe

Still leaning toward a comm related problem.  Are you using the 530 com or the other radio?  Have you tried using opposite radio?  The 530 should take care of the notch filter internally, but the opposite side could be at fault.  Have you tried flying without ELT?  It is a long shot, but easy and one more thing to check off the list.  Have you tried other LPV approaches?  

One simple thing I have seen is a radio not seating in the rack completely after work.  Be sure that the 530 is up against the rack.  Have not seen these symptoms, but you never know.

[Joe Larussa]

So shot the same offending approach for the 12th time in a week. This time everything on but no ELT. Strong satellite reception the whole and no issues.Prevoius ten attempts had issues every time. Uh? So now what? ELT antenna too close to GPS antenna or bad ELT?

[Andy95W]

I’d install a notch filter between the ELT antenna and the cable to the ELT. Simple BNC type connector. 

http://m.aircraftspruce.com/catalog/avpages/tednotch.php?clickkey=57768

[takair]

24 minutes ago, Joe Larussa said:

So shot the same offending approach for the 12th time in a week. This time everything on but no ELT. Strong satellite reception the whole and no issues.Prevoius ten attempts had issues every time. Uh? So now what? ELT antenna too close to GPS antenna or bad ELT?

Is it an older 121.5 ELT?  Can’t recall if you said how close the antennas are.  It is likely an odd combination of the com antenna to ELT antenna spacing and then the ELT to GPS antenna.  Do you have photos or dimensions?  You could also try simple things like swapping the comm coax so you are using the opposite antenna.  Power levels might be different with different results.  I seem to recall that adding a notch filter to the ELT coax may help, but the side effects might not be good.  There are threads on other forums and there used to be an FAA notice on the subject, but I can’t find it now.  Either way, it could come down to making some simple changes in the antenna configuration or it may be an excuse to get a 406 ELT if you dont  have one. 

[takair]

Just now, Andy95W said:

I’d install a notch filter between the ELT antenna and the cable to the ELT. Simple BNC type connector. 

http://m.aircraftspruce.com/catalog/avpages/tednotch.php?clickkey=57768

Have you seen any degradation in ELT performance doing this?  They only seem to have adequate power when they are set off by accident.

[Joe Larussa]

9 minutes ago, takair said:

Is it an older 121.5 ELT?  Can’t recall if you said how close the antennas are.  It is likely an odd combination of the com antenna to ELT antenna spacing and then the ELT to GPS antenna.  Do you have photos or dimensions?  You could also try simple things like swapping the comm coax so you are using the opposite antenna.  Power levels might be different with different results.  I seem to recall that adding a notch filter to the ELT coax may help, but the side effects might not be good.  There are threads on other forums and there used to be an FAA notice on the subject, but I can’t find it now.  Either way, it could come down to making some simple changes in the antenna configuration or it may be an excuse to get a 406 ELT if you dont  have one. 

My ELT antenna is 9" from my Gps antenna. I have a Artex 200 Elt. Looks like manufactured in 2001. 

[takair]

51 minutes ago, Joe Larussa said:

My ELT antenna is 9" from my Gps antenna. I have a Artex 200 Elt. Looks like manufactured in 2001. 

That’s really too close, but before you start punching new holes, you may want to try swapping coax on the comms or try the notch filter that Andy suggested.  I looked up the spec and it should have minimal impact on the primary frequency, but would have your shop test the output to verify.  I’ve used them on comms, just not an ELT...should work the same.  Sounds like you are close to having this solved.

[bradp]

Garmin guidance is something like 2 feet for a gps antenna from a com antenna.  Whomever installed the latest antenna didn’t do it right.  Try the notch filter before anything else.  This is the method by which you can have a “combination antenna” like the Comdats

[Joe Larussa]

7 hours ago, bradp said:

Garmin guidance is something like 2 feet for a gps antenna from a com antenna.  Whomever installed the latest antenna didn’t do it right.  Try the notch filter before anything else.  This is the method by which you can have a “combination antenna” like the Comdats

Pretty sure I have two feet from comm antenna's. It's the ELT that's 9" away.

[Brandontwalker]

I’d install a notch filter between the ELT antenna and the cable to the ELT. Simple BNC type connector. 
http://m.aircraftspruce.com/catalog/avpages/tednotch.php?clickkey=57768

+1. I had exact issue and it resolved with a notch filter. Easy fix.


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