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Lost GPS signal with Garmin 296

Tony Partain

Tony Partain

Well Known Member
I was flying back from Hondo TX on Sunday and my Garmin 296 stopped receiving satellite signals for about 15 minutes. The unit has worked fine for several months. The satellite page was showing a couple of satellites with week signals but would not acquire any more, then about ten minutes later it acquired several and worked fine. The first clue that the signal was fading or being interrupted was the vertical nav feature would stop working. The external gps antenna is mounted on the glare shield and the XM antenna is mounted there too. I?ve used the XM radio several times in the past and it produced no signal problems.

The only thing that has changed is a remote antenna for a XM radio. Has anyone experienced a problem with one of these? Or am I looking in the wrong place? Any suggestions? I called Garmin, but the response was a I dunno.
 
Here on the west coast with all the MOAs and Restricted areas, it's very common to see 'GPS unreliable' NOTAMS for areas bounded by certain Lats/Lons. In our case, the GOVT is degrading the signal for purposes unknown to me. We see what you are seeing on a regular basis. Possibly this happened to you.... :confused: Rosie
 
296

We've infrequently finished a long cross country without GPS dropout like you experienced. Sometimes it's very brief and sometimes longer. I always assumed it was a deliberate government signal degradation or some other signal problem. We've never identified a problem with the GPS receivers. At least in the areas we fly, it seems it's happening less. Makes you wonder about approaches. Bill
 
I bet it had something to do with this... It's from the KZFW, KZAB, and KZHU NOTAMS.

05/005 - GPS IS UNRELIABLE AND MAY BE UNAVAILABLE WITHIN A 330 NM RADIUS OF THE HOLLOMAN TACAN (HMN, 325144N1060633W) AT FL400, DECREASING IN AREA WITH DECREASE IN ALTITUDE TO 280 NM RADIUS AT FL250, 210 NM RADIUS AT 10,000 FT MSL, AND 200 NM RADIUS AT 4,000 FT AGL. THE IMPACT AREA ALSO EXTENDS APPROXIMATELY 230 NM AT FL400 AT THE FURTHEST POINT TO THE SOUTH, DECREASING TO APPROX- IMATELY 110 NM AT 4,000 AGL. 0200-1000 DLY 16 MAY 02:00 UNTIL 20 MAY 10:00
 
GPS signals

Now I'm starting to understand why everyone and their dog wants to launch their own GPS satellite network...
 
me too!

Tony,

I also experienced this as well, but with a 195. I was Southeast of Temple when it happened. I thought it was strange, but then I thought about it and Fort Hood was not too far away. It didn't happen the rest of my trip. Maybe all of the conspiracy folks are on to something ;) . Stranger things have happened.

Todd
RV-10 #362 (empcone almost complete)
 
Update

After flying to the Marysville California fly in I had the same problem again with my 296 . Lost or poor signal reception, this time it was over Klamath Falls OR. Signal faded and the GPS lost it vertical nav.
So I did a little research on the 296 and found an issue. Any software version prior to 4.2 has a lower signal resolution. After updating my software the GPS signals are much stronger. It also picks up more satellites that before. So was it the military or was it Garmin? My bet it was Garmin?s software.
 
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Garmin GPS and your radios

I had a similiar problem with a Garmin 195 going out in a specific area.
Called Garmin support. Turned out that when I tuned my nav radio to that airport's localizer, the RF took out the GPS.
NOTE: Not transmitting, just receiving that freq took out the GPS!!
This was a known issue for Garmin. Tech support knew several freqencies that were a problem with my radio (Narco). Some were Comm frequencies.
They had a list for other radios as well.
 
Tony Partain said:
So I did a little research on the 296 and found an issue. Any software version prior to 4.2 has a lower signal resolution. After updating my software the GPS signals are much stronger. It also picks up more satellites that before. So was it the military or was it Garmin? My bet it was Garmin?s software.
Click to expand...

FYI, I believe it was only software version 4.00 for the 296 that had the problem, which was fixed in 4.10.

cheers,
mcb
 
markscogg said:
I had a similiar problem with a Garmin 195 going out in a specific area.
Called Garmin support. Turned out that when I tuned my nav radio to that airport's localizer, the RF took out the GPS.
NOTE: Not transmitting, just receiving that freq took out the GPS!!
This was a known issue for Garmin. Tech support knew several freqencies that were a problem with my radio (Narco). Some were Comm frequencies.
They had a list for other radios as well.
Click to expand...


My experience is that the Mark 12D and the 296 are incompatible. The 12D kills my GPS reception, and the GPS interferes with both the RX and TX on the 12D. I contacted Garmin, but had no response at the time.

FYI, the GPSMap III and Lowrance units operated properly.

I don't fly in the interfering aircraft anymore.

Vern Little
 
FYI, I believe it was only software version 4.00 for the 296 that had the problem, which was fixed in 4.10.
Click to expand...


My version was 3. something and the 4.2 made a significant difference in the signal.
 
new gps decoding?

Well... what does that mean for "us"? For our future GPS purchases... will we be looking for the SAASM stuff? Do we need to be aware of these items in our future equipment considerations and integrations? What will the FAA do about signal degregation with the FAA approved gps approaches? Is this another 7,000$ debacle for "us"? I'm aware of the rule change on ELT beacons as of 2009 to gps encoding.... will the saasm hamper the rescue efforts of future accident victims.... Gentlemen... It's time to get involved... there could be many future ramifications for all of us.
Brian
 
Brian,

brianwallis said:
I'm aware of the rule change on ELT beacons as of 2009 to gps encoding
Click to expand...
not sure to what rule you're referring to... the 2009 date is the cut-off for support of the 121.5 ELT frequency, but the switch to 406 MHz does not imply that we will be forced to have a GPS capable ELT.

http://www.sarsat.noaa.gov/phaseout.html

Of course, it's best to have a GPS signal fed into the ELT, but as of today, it looks like most ELTs on the market don't yet have such feature.

I'm sure there will be plenty of new products before the Feb 1st 2009 deadline expires.

Bye, Luca
 
It just reinforces the need to utilize a chart as a back up while flying. There are many things that can cause a GPS to be unusable.

Glad you didn't have any problems.
 
praterdj said:
It just reinforces the need to utilize a chart as a back up while flying. There are many things that can cause a GPS to be unusable.
Click to expand...

Very true, the back up chart should be essiential. But I wonder what the "real" failure rate of picking up a workable GPS signal is? At least in the northern hemisphere with WAAS.

Must be less than a fraction of 1%. I always see a few, who believe that GPS should be utilized as just the backup, and make statements that it's rather un-reliable. I find these statements to be a bunch of baloney.

Of course, if someone has authentic data on the subject, I'd like to see it. In the meantime, I'll continue my avid ramblings for the use of moving map GPS. Preferably with topography data & terrain warning.

L.Adamson --- Garmin 296
 
Update to the Update.

Ok sometimes it takes a little time but eventually you get to the bottom of the issue.

First when I did the software update to the GPS my test to see if the signal improved was to pull the plane out of the hanger and turn on the GPS. This produced the results of an improved signal that I was looking for, so I called it a day. But the real issue was still hiding under the glare shield. I went flying again and the GPS signal was degraded again. So I started turning everything off in sequence, all the way down to the master. The master did it, the signal came up to what it was when I pulled the plane out of the hanger to test it. So what the h*%% is it? Sitting on the ground I turned on the master and the GPS then started to move the coil of excess wire and the signal came up again. Thinking the wire was to close to something that was emitting a signal so I moved it. But as soon as my hand was removed the signal came back down. So next I removed the screws from the antenna to try a different placement. When the antenna was placed more than 9 inches from it original placement it would work fine.

So it turns out that the LCD clocking signal from the engine monitor was interfering with the antenna that was placed way to close. When the canopy was down the antenna was with in inches of the screen.

No aliens, no secret government conspiracies or crazy manufacturing problems, just a placement issue. All in all very easy fix by the process of elimination. Of course now I have a hole in the glare shield so I need to finish the leather glare shield cover. It may be flying but its never done. :rolleyes:
 
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Tony,

Thanks for providing the update. This will allow us to build around this in our planes and hopefully avoid this issue. I fly primarily with my GPS but I always track my progress on a chart for back up. It helps to pass the time and keeps me occupied on flights over featureless terrain.
 
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