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  #1  
Old 03-13-2020, 03:22 AM
jelliott82 jelliott82 is offline
 
Join Date: Oct 2018
Location: Dunedin, New Zealand
Posts: 17
Default Garmin GPS-20A Reception Issue

Hello

I cannot get my Garmin GPS-20A to find a GPS signal in my RV7 build. I have taken the fuselage outside with a clear view to the sky (GA35 mounted on the top of the rear turtle deck externally) and tried orientating the aircraft in 2 different orientations 90deg to each other while leaving it for about 5 minutes to try and establish a signal. What I end with the Unit Status LED solid Green, and the GPS Status LED slow flashing Green. The screen on the G3X is shown in the attached photo. Is there some trouble shooting steps I can try? Also are the GPS-20A units compatible world wide? ie If I had an American supplied unit (not sure if this is the case as I ordered through the local Garmin dealer here) would it function perfectly well in New Zealand ... ie frequencies the same etc?

https://ibb.co/j64k3Gm

Thanks,
Jonathan
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  #2  
Old 03-13-2020, 09:55 AM
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wjb wjb is offline
 
Join Date: Nov 2012
Location: Half Moon Bay, CA
Posts: 949
Default

You seem to be definitely missing some satellites there ... the 20A is compatible worldwide (just like the GPS in your phone). You have a good quality antenna (same as my setup) ... I'd suspect the cable. Inspect the ends to be sure the center pins are fully inserted into their bodies (they should almost be flush with the end of the plastic inner insulator), and ohm out the cable to be sure the center conductor and shield make good contact with the center pins and connector bodies, respectively, and and there no short between the two. You should also see voltage on the center pin to shield (2.5 to 5 VDC, I don't remember the exact value) to power the amplifier in the antenna ... check this at the antenna end of the cable.

Another thing ... you say that the unit status LED is solid green (install manual section ... 36.1.1 Status LED) implies that the unit is on but not communicating over the CAN bus. What's the status of the unit on the configuration page in G3X? Does the PFD see it?
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Last edited by wjb : 03-13-2020 at 10:09 AM.
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  #3  
Old 03-13-2020, 11:22 AM
Pdtofly Pdtofly is offline
 
Join Date: Jan 2012
Location: Reno, NV
Posts: 319
Default GPS-20A

Jonathan,

First, my wife went to med school at Otago Uni in the 80’s. Someday, she hope to return there for a visit, and me, see it for the first time. She keeps showing me photos of the Uni, and it looks beautiful.

Second, beside checking what was in the previous post, how old is your antenna? I see you said you have a GA35. Garmin years ago turned out a batch of these antennas that failed, and many had to be replaced for free. Check your serial number and see if it was in that batch, and if so, get it replaced.

Third, check all your connections to all the can-bus modules, and be sure if the GPS is at the end, that it is terminated correctly. The Unit Status LED steady green means the unit is powered On, but not communicating via CAN Bus. The GPS status flashing slowly means you unit is acquiring a position with good signal to noise, but has not locked on. When it flashes fast, you are locked on.

Now, it is not locking on, so the areas to look at are the antenna, coax between antenna and GPS, or the GPS unit. You also could have a bad antenna or GPS. It also is saying you have it powered up, but it is not communicating via the can-bus either.

First find out why you you are not communicating with the GPS via the can-bus and get that light flashing. That might fix the problem, if not, you have one problem fixed. Then check out the coax next, then the antenna.

If you want some more help, email me directly at hr2plt@yahoo.com, and we will see how to get you up and running.

Good luck.

Brian

Last edited by Pdtofly : 03-13-2020 at 11:27 AM.
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  #4  
Old 03-13-2020, 11:31 AM
BobTurner BobTurner is offline
 
Join Date: Dec 2011
Location: Livermore, CA
Posts: 6,242
Default Probably okay

5 minutes is not long enough. To dig these weak signals out of the noise, the box has to guess at about where it is. For a new Garmin box, the first guess will be Olath, Kansas. It will take time to move the guess to NZ! Give it a full 30 minutes, with a good view of the full sky. Once it locks onto one satellite it will quickly find others, and in the future it will start its search in NZ. You can follow the progress on the sattellite page.
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  #5  
Old 03-13-2020, 01:32 PM
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wjb wjb is offline
 
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Location: Half Moon Bay, CA
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5 mins may not be enough to pull down all the data from the satellite's nav message downlink, but, the receiver will lock on and track the satellites well within 30 seconds. You should see multiple grey bars on the PFD, which turn green when the nav data is available and it is contributing to the position solution. Multiple grey bars is an early indication that the 20A has started track satellites.
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Log at: http://rv7.wbencze.com
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  #6  
Old 03-14-2020, 06:57 PM
smt6 smt6 is offline
 
Join Date: Apr 2013
Location: SoCal
Posts: 197
Default

I had a similar issue when I installed mine. It ended up being the connector on the antenna. Ended up wasting an expensive 90 degree TNC connector because of it.
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  #7  
Old 03-16-2020, 09:43 AM
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UnPossible UnPossible is offline
 
Join Date: Jan 2008
Location: Granbury, TX
Posts: 530
Default

I had a similar issue when I installed the GPS-20A in my 7A.... I checked and rechecked the wiring, re terminated all my connections... etc

When nothing worked, I called Garmin and they told me it could take 5-10 minutes to lock in the first time. I pulled the plane out of the hangar, turned it on and walked away for 15-20 min.... when I came back it was locked in.

I don't think I had a problem at all, I just need to wait longer for it to lock in.
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  #8  
Old 03-16-2020, 11:56 AM
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g3xpert g3xpert is offline
 
Join Date: Sep 2010
Location: Olathe, KS
Posts: 2,718
Default GPS 20A

Quote:
Originally Posted by jelliott82 View Post
Hello

I cannot get my Garmin GPS-20A to find a GPS signal in my RV7 build. I have taken the fuselage outside with a clear view to the sky (GA35 mounted on the top of the rear turtle deck externally) and tried orientating the aircraft in 2 different orientations 90deg to each other while leaving it for about 5 minutes to try and establish a signal. What I end with the Unit Status LED solid Green, and the GPS Status LED slow flashing Green. The screen on the G3X is shown in the attached photo. Is there some trouble shooting steps I can try? Also are the GPS-20A units compatible world wide? ie If I had an American supplied unit (not sure if this is the case as I ordered through the local Garmin dealer here) would it function perfectly well in New Zealand ... ie frequencies the same etc?

https://ibb.co/j64k3Gm

Thanks,
Jonathan
Jonathan,

The GPS status LED will be slow flashing green as it is acquiring, and will be flashing green quickly, as a GPS fix is locked in. If it is slow flashing green, you may just want to give it some time to find a fix.

The Unit status LED however should be flashing green. If it is steady green, that means the unit is powered, but not communicating via CAN bus. You would want to look at the system status page to determine whether or not the GPS 20A has any bus errors associated with it.

Let us know what you find. You may also reach out to us directly at G3Xpert@Garmin.com.

Thanks,

Justin
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