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  #1  
Old 11-15-2013, 05:52 AM
Smilin' Jack Smilin' Jack is offline
 
Join Date: Jan 2011
Location: Cumming, Georgia
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Default Dynon mode S

If any one here is running a dynon SV261 with the Dynon ADS-B have you ever checked with center or approach control to verify that they are receiving the block containing your N Number.
I am running dual Dynon's with the above transponder and during my transponder check with the local avionics shop they do not show the Mode S in limits under the sensitivity and thus my mode S is not being transmitted. This is the second xponder from Dynon. Center is receiving the mode C altitude read out just fine but they do not show the block that should be displayed with the N number.
I have full ADS function

The n number show up on the test unit but because the sensitivity is out of the db range it is not transmitting it?

Dynon is working with me on this... But they use a out source avionics shop for their repairs.


Any ideas?
Smilin' Jack
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  #2  
Old 11-15-2013, 07:10 AM
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Walt Walt is offline
 
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Default

Sounds like an antenna/cable issue. A quick bench check should confirm the unit is within spec.

The low sensitivity would have nothing to do with the data block however.
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  #3  
Old 11-15-2013, 08:39 AM
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Bill_H Bill_H is offline
 
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Location: Marshall TX (KASL)
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I assume when you say Dual Dynon you mean the Skyview EFIS is dual. All serial connections must be paralleled to each EFIS - that became a requirement in one of the Skyview software upgrades. Sometimes one EFIS is primary, sometimes the other one - depends on power-on stuff. So be sure that is done. (You probably have, but others may not have/be aware.)
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  #4  
Old 11-15-2013, 10:11 AM
guccidude1 guccidude1 is offline
 
Join Date: Mar 2008
Location: Reno NV
Posts: 546
Default Dynon mode S

I have the Dynon 261 and 470 installed. I asked NorCal recently if they could see any additional info other than my tx code and alt. The controller said they don't usually have "that stuff up and running". Oh well, Dan
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  #5  
Old 11-15-2013, 08:48 PM
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dynonsupport dynonsupport is offline
 
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Location: Woodinville, WA
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Default

As Dan says, the fact that center can't see your N number doesn't tell you anything.

Most radars in the USA are not Mode-S. Thus, they cant see your Mode-S data, such as the N number. On top of that, even if the radar is Mode-S, the link between it and center may not be Mode-S compatible, so Center only gets the Mode-C data.

So, the real question for center is "can you usually see general aviation aircraft at my altitude and location with N numbers?" Airliners that are 4 miles above you don't count since a different radar may be getting them. Unless center is sure that the radar painting you is Mode-S capable and so is the data link, they aren't the ones that you should be using to determine there is an issue.

Additionally, if this is the second transponder with an issue, then the chances are 99.9% that if there is an issue, it's in the plane. These are fully TSO'd units made in a PMA'd factory, and they have a phenomenally low failure rate, much less any out-of-the box failures.

Remember that Mode-S is just a burst at the end of Mode-C. It's not a different frequency or different hardware. If Mode-C is working, it's not like there is really a hardware failure that can mess up Mode-S.

If your transponder test guy said the Mode-S interrogation sensitivity is too low, then you need to have him hook the test set right to the transponder, and verify that the transponder itself meets the TSO for sensitivity. Once you see that it does, then you can investigate why your install in general does not meet the requirements. What kind of cable did you use to hook up the transponder to your antenna and how long is it?

Also, if ADS-B out is working and you are getting "ADS-B FULL" as a traffic status, your N number *IS* being broadcast and the ADS-B ground station is getting it. Without this you won't get ADS-B FULL.

--Ian Jordan
Dynon Avionics
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  #6  
Old 11-16-2013, 01:35 PM
SteinAir SteinAir is offline
 
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Location: Minneapolis
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Ian is spot on here. Our experience has been that the chance of one of those transponders being bad is possible, but not very probable...by the time you get to two of them acting the same way, the statistics are such that the likelihood of them both being bad is beyond measurable odds.

As mentioned by a couple folks, the lack of an "S" datablock in itself doesn't tell us much, but the transponder test result tells us more. Assuming the shop doing the test was using one of the better higher end test boxes to do the test, it'd be easy to hook it up directly to your transponder and eliminate the cabling or the antenna. We've seen this before too (multiple times) and every time it's been a coax cable that tested good with a simple multimeter, but actually had some problems. Usually crimping on new ends solves that.

Also, one should separate the ADSB though process with the simple transponder operation (like Walt mentioned, the data block and sensitivity aren't the same thing)...and what the transponder sends when won't have a bearing on your output or sensitivity per say.

Before I spent too much time sending stuff back/forth or repairs, I'd have someone hook a box up directly to your transponder and have a peek. It usually doesn't take but a few extra minutes during the test to do that (assuming relatively easy access to your transponder). Like I said, it's certainly possible you have a bad box(s), but it's just not very probable...especially with that particular box. We have now worked with hundreds of these transponders and have seen exactly two of them sent in for repair (got blown up by the builder).

Just my 2 cents as usual.
Cheers,
Stein
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  #7  
Old 11-17-2013, 01:48 PM
Smilin' Jack Smilin' Jack is offline
 
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Ian, Stein Dan and others,
The shop has on both units hooked directly up to the transponder, and this is the issue.
The box goes through various sensitivity of the mode a,c, and s. A and a lot of other test that I do not understand.
With the sensitivities shown as -62db but since the mode s is out side of the of the db readings by more than 1 db it fails the test. The db reading on the mode s is around -52db
The test unit does see the fact that the ICAO address is correct and does see the N umber that is programmed into the xponder via the settings on the xponder setup on the Skyview.

I would agree with all the above statements if we had not hooked directly up to the xponder to verify the test because he too stated that with a test unit outside of the aircraft it can fail due to location.

My understanding is the first unit is being sent to Dynon's repair facility and they are suppose to notify us of their findings. That facility also is used by Hawk Avionics for some of their repairs and they have high regard for them.

Thanks for the input. I guess the mode S is not quite the same as the TCAS II v7 and flight ID we have on our corporate jet. But Atlanta center did state that they are Mode S capable and occasionally see N numbers displayed on smaller aircraft and it is not a tag they put on the beacon.

I also have seen on the foreflight display while working with a stratus unit n numbers displayed at various airports but fairly limited only at some airports like Denver.

Jack
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Last edited by Smilin' Jack : 11-17-2013 at 01:58 PM.
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  #8  
Old 11-17-2013, 03:37 PM
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Radomir Radomir is offline
 
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Quote:
Originally Posted by Smilin' Jack View Post
Thanks for the input. I guess the mode S is not quite the same as the TCAS II v7 and flight ID we have on our corporate jet.
Technically, it is the same thing -- it's all just one field of specific Mode S message formats but it's not being broadcasted all the time in the blind..

Don't confuse that with what Foreflight shows because that throws in ADS-B into the picture and that's a different animal.

To further confuse things, your unique hex address is sent with ALL Mode S messages sent by the txp, but Flight ID is not (sent only sometimes, typically only when interrogated -- so if no one asks you for it, it won't be sent out). Different systems work differently which determines what kind of info is sent out and when.. so you may see slightly different behavior on a corp jet equipped with v7 TCAS..
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  #9  
Old 11-17-2013, 06:33 PM
Smilin' Jack Smilin' Jack is offline
 
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Thanks for clearing? That up....
No really there is so many systems unique to different aircraft it is some times hard to keep it all straight.
Jack
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CE500, LRJT, HS25, C650, SBJT, CL60
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  #10  
Old 11-17-2013, 07:06 PM
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GalinHdz GalinHdz is offline
 
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One way you can check it is after you make an IFR flight go to Flight Radar, enter the time you were flying and see if you show up as an ADSB track with your aircraft data IF you are within range of an ADSB capable ground station.


Last edited by GalinHdz : 11-17-2013 at 07:10 PM.
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