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430W dropouts & Ant location

lr172

Well Known Member
I upgraded from a KLN to a 430W not long ago. While I have had no issues in the first 10-20 hours, I had 2 complete dropouts (wihin 15 minutes of each other) enroute to Asheville a week ago. They were both complete failures, dropping to dead reckoning mode for about 5 minutes each. I had 3 other GPS's onboard and neither experienced the failure.

The 430 just came back from Garmin doing the Waas upgrade and included a new antenna. The antenna is mounted on a shelf under the cowl, where I have my other GPS antennae, which have never experienced a signal loss. I once got a RAIM warning on the KLN during an approach, but that is to be expected occasionally on the the non-waas units.

I am looking for some guidance with this. Clearly it wasn't a lack of sat signal, as the other units worked. I am wondering if this could be a problem with the unit or possibly with my antenna location. I am willing to move it to the top exterior, if necessary, but thought I would try the under cowl location to see if it worked. I do have 19' of cable coiled up under the panel. I suppose it could be a bad connection, but would have expected a failure in the prior 20 hours and higher vibration conditions.

Any thouights? Should I move the antenna up high? I need to rely upon this unit for GPS approaches.

Larry
 
I had a similar problem. I have 2 430w installed 1 dropped out the other kept running. The antenna are external behind the rear window on top. Side by side. I swapped the connections first at the Antenna first and nothing changed. When I swapped them back things came back on line again. Had no problem scince. All this after about 10 hrs of operations with no problem. Started to paint the RV the other day and found loose screws o the Antenna holding it to the body. I suspect it was a earth problem that caused my problem after speaking with a avionics guy. May be a similar problem that you have
 
Try this. With the 430W on the satellite signal page, key the 430 radio. If the signals drop you have the "known" problem I had on my GTN-650.

If so, repeat the test after you:
- disconnect the ELT (turn it off and disconnect the antenna)
- disconnect your second radio (turn it off and disconnect the antenna)

Let me know the test results.
Carl
 
I had a similar problem. I have 2 430w installed 1 dropped out the other kept running. The antenna are external behind the rear window on top. Side by side. I swapped the connections first at the Antenna first and nothing changed. When I swapped them back things came back on line again. Had no problem scince. All this after about 10 hrs of operations with no problem. Started to paint the RV the other day and found loose screws o the Antenna holding it to the body. I suspect it was a earth problem that caused my problem after speaking with a avionics guy. May be a similar problem that you have

Does the 430W antenna require a ground plane? I had assumed that it did not. The AL piece that the antenna sits on is pretty small, but it is grounded to the airframe. The antenna was firmly attaced when installed, but haven't checked recently.

Thanks for sharing your experience.

Larry
 
Try this. With the 430W on the satellite signal page, key the 430 radio. If the signals drop you have the "known" problem I had on my GTN-650.

If so, repeat the test after you:
- disconnect the ELT (turn it off and disconnect the antenna)
- disconnect your second radio (turn it off and disconnect the antenna)

Let me know the test results.
Carl

Thanks for the suggestion. I do most of my flying in controlled airspace and transmit a lot with no noticeable failure. I am pretty sure that both failures occurred at times that I was not transmitting.

Larry
 
Personally I won't put an ifr antenna under the cowl. Too hot. More likely, it's known that the preamps can sometimes radiate spurious signals. I wouldn't put another GPS antenna close by. Finally, 19' of cable sounds lossy to me. I know some systems require a certain minimum loss, but as I said that sounds like a lot. Try Carl's suggestion to monitor the signal levels.
 
Gps

Turn your 430w on the satellite reception screen, then take a handheld GPS receiver (also turned on) near your antenna and watch the bars drop as you move the handheld closer to your 430's antenna. I don't understand why but the antennae can interfere with each other if they're too close. I think it's some kind of resonance. John
 
I chased this problem for a couple years - an intermittent and unpredictable loss of gps signal. It was a flaky antenna. Antenna changed, and no problems for several years now.
 
Thanks for the insights here. Given that I have 2 other GPS antennae, in addition to the 430 antenna, it probably makes the most sense to move the 430 antenna to the top and out of the heat and away from the other antennae.
 
Old thread, same issue.

I know this thread is over a year old but I started having the same issue after 5 years of flawless operation. Mine drops out after about 10 minutes from lift off and has nothing to do with radio transmission. I checked all the connections at the antenna and the rack, all good.

My antenna is mounted under a fiberglass hatch in front of the wind shield. Again, 5 years of flawless operation!

Never saw the results or fix of this problem. Was it the antenna?

Thanks,
 
2 suggestions. 1 if you upgraded to WAAS, it requires a different antenna than non WAAS. Probably you know this. Not well know is the minimum antenna cable length, yeah minimum. They require a certain antennuation of the signal. No idea if this is your problem, but there it is just in case.
Tim Andres
 
In my Lancair I've seen this for 15 years. First with my 430 and then later with my 430W. Changed the antenna and the cable when I upgraded. The antenna is in the back under the fiberglass, nothing around it. It just happens every so often in straight level flight. After a few minutes it comes back on. I don't know why, Garmin I guess. MGL iEFIS GPS screens don't never drop out. Antenna up under the glare shield.
 
No. I moved the antenna to the top of the fuse and never experienced another outage in probably 100+ hours. I am convinced from this experience that the location under the cowl is sub-optimal, at least for the 430W. I have yet to have an outage from the GRT or 396 with antenna's in that same under cowl location. I observed signal strength readings on the 430 before and after the move. Much better signal reception on top.

My installation was with a brand new antenna and the required 25' of RG-400. Same setup was used in both locations.

Larry


I know this thread is over a year old but I started having the same issue after 5 years of flawless operation. Mine drops out after about 10 minutes from lift off and has nothing to do with radio transmission. I checked all the connections at the antenna and the rack, all good.

My antenna is mounted under a fiberglass hatch in front of the wind shield. Again, 5 years of flawless operation!

Never saw the results or fix of this problem. Was it the antenna?

Thanks,
 
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Tim2542, always been a 430W, no upgrades or changes and the required cable length has always been there. I haven't made any changes at all and the first 5 years are flawless!

Larry, thanks. Did it work ok when first installed in original position under the cowl and then slowly start to fail? My antenna is mounted under a fiberglass cover in the forward skin just in front of the glare shield/ wind screen.

Christer from Stein is having me do a vibrating test as the antennas sometimes go bad due to vibration. That test this weekend.
 
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Tim2542, always been a 430W, no upgrades or changes and the required cable length has always been there. I haven't made any changes at all and the first 5 years are flawless!

Larry, thanks. Did it work ok when first installed in original position under the cowl and then slowly start to fail? My antenna is mounted under a fiberglass cover in the forward skin just in front of the glare shield/ wind screen.

Christer from Stein is having me do a vibrating test as the antennas sometimes go bad due to vibration. That test this weekend.

The mounting was on a shelf a few inches forward of the firewall and one inch under the cowl. I had the KLN-90 antenna installed there with no problems, so put the 430W antenna there as well. Seemed to work well for 30 hours or so and then had two 3 minute signal losses on a long x country trip. No noticeable issues before that, though they may have existed. I would only notice the signal loss if I was tracking a course via the EFIS and I rarely do that on local flights.

I was concerned about losses during an IFR approach, so I wasted no time in finding a resolution. I do not believe my mountaing location would have any more vibration than the glareshield of a sliding canopy plane and many have antenna's mounted there without issues. My shelf was supported by the firewall. If the issue for me were vibration, I don't believe that I would have seen the improved reception levels after moving the location. I observed the GPS status page before and after the move. I could see vibration causing a signal loss, but not degraded reception levels.

Larry
 
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Does the 430W antenna require a ground plane? I had assumed that it did not. The AL piece that the antenna sits on is pretty small, but it is grounded to the airframe.
Larry

?Ground plane? is an unfortunate name. Being grounded to the airframe is irrelevant.
Remember that the gps ?engine? in a 430W is now one, maybe two, generations behind. But the TSO makes upgrading it too expensive.
IMHO if you?re going to use this for actual IMC then you should follow the TSO instructions. Install the antenna externally.
 
‘Ground plane’ is an unfortunate name. Being grounded to the airframe is irrelevant.
Remember that the gps ‘engine’ in a 430W is now one, maybe two, generations behind. But the TSO makes upgrading it too expensive.
IMHO if you’re going to use this for actual IMC then you should follow the TSO instructions. Install the antenna externally.

Bob,

I moved it externally a year ago and it solved my issues. Now that you mention this, I expect the ground plane is probably the best explanation for the degraded reception in the fwd mounting location. The plate was only 6" X 6" and I assumed that I was getting a larger ground plane by being electrically bonded to the air frame.

Clearly some people are having success with this, but I believe it is operating near the fringes of reception and it introduces risk for IFR flight, as the right conditions will allow it to drift across the fringe area and drop the lock.

Larry
 
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Bob and larry,

I totally understand your points. My only thought is that it was fine for five years. I am leaning towards a failed or failing antenna. In its current location, it is mounted to an aluminum pan connected to and surrounded by the front skin with the only differance is that it is mounted just below the level of the top skin but with a lot of clearance around it. All covered by a thin fiberglas panel. After this weekends vibration test, I will decide on moving the exiting antenna to a new location or purchasing a new antenna and mounting it in the same position as the existing.

I just wish there was a clear way to determine if the antenna is bad or not.
 
I know this thread is over a year old but I started having the same issue after 5 years of flawless operation. Mine drops out after about 10 minutes from lift off and has nothing to do with radio transmission. I checked all the connections at the antenna and the rack, all good.

My antenna is mounted under a fiberglass hatch in front of the wind shield. Again, 5 years of flawless operation!

Never saw the results or fix of this problem. Was it the antenna?

Thanks,

Do you have any other GPS's on board and if so, do any of them lose lock when the GNS drops out?
 
Bob and larry,

I totally understand your points. My only thought is that it was fine for five years. I am leaning towards a failed or failing antenna.

I certainly don?t know the specifics in your case. But most modern electronics (and it?s highly likely there are solid-state devices within your antenna) show a statistical decrease in lifetime with increasing temperatures. You might think they either worked, or instantly failed, but apparently that?s not the whole story. And the engine compartment does get very warm, especially after shut down.
 
Bob and larry,

I totally understand your points. My only thought is that it was fine for five years. I am leaning towards a failed or failing antenna. In its current location, it is mounted to an aluminum pan connected to and surrounded by the front skin with the only differance is that it is mounted just below the level of the top skin but with a lot of clearance around it. All covered by a thin fiberglas panel. After this weekends vibration test, I will decide on moving the exiting antenna to a new location or purchasing a new antenna and mounting it in the same position as the existing.

I just wish there was a clear way to determine if the antenna is bad or not.

You need to look at the status page when it fails. No reception would point toward a failing antenna and a weaker than normal reception would point to a bad location. This guidance follows what I received directly from Garmin tech support. As I mentioned, a saw an improvement in reception strength with the move and was all that I needed to convince myself that the location was sub-optimal.

I certainly wouldn't spend 100's of dollars on a new antenna without trying a location that has been shown to have better signal strength. My gut tells me there is a reason Garmin want's it externally mounted. And to Bob's point, I wouldn't put the new antenna in the old location. Most get far more than 5 years of life from their antenna.

Larry
 
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Brian, two others and none have ever dropped out

Bob, good points, not mounted in the engine compartment so heat isn't an issue. Area is just in front of and just above the electronics bay and has cooling fan.

Larry, all good points. Been trying to get it to fail again so I can check statins but as luck would have it.......
 
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