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1090MHz Filter for ADSB 472 Issues? (Read 937 times)
Jan 12th, 2018 at 2:27pm

TurboPilot   Offline
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Much too early to declare victory but I just installed a FlightAware 1090MHz Mode S Filter on the antenna lead of my ADSB 472.

https://www.amazon.com/gp/product/B010GBQXK8/ref=oh_aui_detailpage_o05_s00?ie=UT...


Made one long flight in and out of coverage. There is absolutely no doubt my ADSB 472 is working better than before. I immediately noticed on the ground I was receiving a signal from a nearby tower much sooner and held that signal taxiing around. The traffic returns in and out of coverage were solid with very few drop outs. I flew it watching the output of an ADSB Scout on my iPhone using FlightAware. ADSB 472 pulled in traffic and weather sooner and kept it on the screen better compared with the Scout.

I know Dynon says there are software issues too but after this flight with the filter my, ADSB 472 seems to be working "normally".

Again one flight is not a test program but it only costs $14.95, so it is worth a try.

...
 
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Reply #1 - Jan 12th, 2018 at 4:53pm

Garrett   Offline
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I just ordered one  Cheesy
 
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Reply #2 - Jan 12th, 2018 at 5:18pm

TurboPilot   Offline
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Garrett wrote on Jan 12th, 2018 at 4:53pm:
I just ordered one  Cheesy


You will need these SMA to BNC adapters to patch into the antenna cable.

https://www.amazon.com/gp/product/B017SOLCMU/ref=oh_aui_detailpage_o05_s00?ie=UT...


https://www.amazon.com/gp/product/B00CVQJRUA/ref=oh_aui_detailpage_o06_s00?ie=UT...
 
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Reply #3 - Jan 12th, 2018 at 6:37pm

Garrett   Offline
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Thanks, I was noticing this last week while looking for a new ADS-B antenna and was thinking about it myself. You made my mind up. Thanks
 
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Reply #4 - Jan 12th, 2018 at 7:26pm

Steve W.   Offline
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TurboPilot wrote on Jan 12th, 2018 at 5:18pm:
Garrett wrote on Jan 12th, 2018 at 4:53pm:
I just ordered one  Cheesy


You will need these SMA to BNC adapters to patch into the antenna cable.

https://www.amazon.com/gp/product/B017SOLCMU/ref=oh_aui_detailpage_o05_s00?ie=UT...


https://www.amazon.com/gp/product/B00CVQJRUA/ref=oh_aui_detailpage_o06_s00?ie=UT...


If it's not a huge pain, I'd make a new coax w/ RG400 and a crimped-on SMA connector.  You can get 'em lots of places.

I don't care for adapters if I can avoid them...
 
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Reply #5 - Jan 12th, 2018 at 7:29pm

jakej   Offline
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As an FYI - those filters are not the total answer for us 'downunder' so I'd suggest people from here do not shell out the bucks until either Dynon chimes in or the stated software fix ? is done.
 
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Reply #6 - Jan 12th, 2018 at 7:44pm

TurboPilot   Offline
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jakej wrote on Jan 12th, 2018 at 7:29pm:
As an FYI - those filters are not the total answer for us 'downunder' so I'd suggest people from here do not shell out the bucks until either Dynon chimes in or the stated software fix ? is done.


At this point I am happy with a better answer if not the total answer. As I said after two flights today there is no doubt my 472 is working better. Certainly worth $14 till something better comes along.

My Carbon Cub seems to have a fair amount of RFI among the boxes, so I may be a special case where filtering helps.

The big difference I noticed today was the persistence of traffic targets using 1090 plane to plane. Since installing the 472 those targets tended to come and go. Today they seemed to be solid continuous targets.
 
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Reply #7 - Jan 12th, 2018 at 8:14pm

Garrett   Offline
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In reading the customer reviews on Amazon the filter seems to help in areas of high cell tower congestion. This seems to correlate with what I am experiencing with the 472.
 
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Reply #8 - Jan 12th, 2018 at 8:31pm

TurboPilot   Offline
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Garrett wrote on Jan 12th, 2018 at 8:14pm:
In reading the customer reviews on Amazon the filter seems to help in areas of high cell tower congestion. This seems to correlate with what I am experiencing with the 472.


Saw that. Since cell phones are barking the same frequencies, I wonder. My cell phone in my pocket is less than two feet from the ADSB antenna on the belly of the airplane.
 
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Reply #9 - Jan 13th, 2018 at 7:32am

Garrett   Offline
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The original 470 great, maybe it had a better designed tuning circuitry.
 
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Reply #10 - Jan 13th, 2018 at 1:19pm

Steve W.   Offline
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TurboPilot wrote on Jan 12th, 2018 at 8:31pm:
Garrett wrote on Jan 12th, 2018 at 8:14pm:
In reading the customer reviews on Amazon the filter seems to help in areas of high cell tower congestion. This seems to correlate with what I am experiencing with the 472.


Saw that. Since cell phones are barking the same frequencies, I wonder. My cell phone in my pocket is less than two feet from the ADSB antenna on the belly of the airplane.


Would be an easy test...just turn it off.
 
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Reply #11 - Jan 13th, 2018 at 3:27pm

Garrett   Offline
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Received the filter from Amazon this morning and installed. After takeoff the 472 started receiving the same time the Garmin 696/GDL39 showed receiving and stayed in receiving until I landed. The filter fixed this issue. I maneuvered about 10 miles south of KVDF for 15 minutes. Although the 472 always showed receiving the ADS-B message was toggling between Full ADS-B, Partial ADS-B and TIS only. Traffic on the screen was lost 1 time during a turn, overall traffic seemed to work better for the area I was flying in. I like the filter. Smiley
 
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Reply #12 - Jan 13th, 2018 at 3:56pm

TurboPilot   Offline
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Good. Got a call from Dynon. They wanted my diagnostic file for the flights with the filter which I sent. You may want to send your files as well with the filter.

Did some hangar flying today. Since I have worked on the unit so much in the hangar I was familiar with it's previous signal reception behavior before the filter.

Before the filter I would typically see the ADSB receiving for short periods but never enough to download a full round of weather. ADSB plane to plane targets would show up and quickly disappear line of sight out the open hangar door.

Today with the filter and sitting in the hangar with door open it downloaded a full round of weather immediately. Traffic going by in the pattern was showing up very well line of sight out the door with very little drop out.

Here is a screen shot "flying" in the hangar.

...
 
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Reply #13 - Jan 13th, 2018 at 6:37pm

Alexe   Offline
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It’s somewhat interesting that even though the status shows “ADS-B NO RADAR” in the capture above, two of the four targets do not show tail numbers. Were they UAT boxes in ‘STEALTH’ mode or ??????? Seems a bit strange to me.
Alex
 
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Reply #14 - Jan 13th, 2018 at 7:19pm

TurboPilot   Offline
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Alexe wrote on Jan 13th, 2018 at 6:37pm:
It’s somewhat interesting that even though the status shows “ADS-B NO RADAR” in the capture above, two of the four targets do not show tail numbers. Were they UAT boxes in ‘STEALTH’ mode or ??????? Seems a bit strange to me.
Alex


I have seen this before when flying Scout ADSB through ForeFlight. Same target on the Dynon had no tail number while the same aircraft displayed on ForeFlight had a tail number.

Could be some of the software issues with the 472.
 
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Reply #15 - Jan 13th, 2018 at 8:31pm

dwightsmall   Offline
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I ordered mine tonight.  Hope the band-pass filter is the solution.  Can't wait to install and will report results.  I think the 470/472 problem has been particularly bad here in the Tucson metro area.
 
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Reply #16 - Jan 14th, 2018 at 6:22am

GalinHdz   Offline
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dwightsmall wrote on Jan 13th, 2018 at 8:31pm:
I ordered mine tonight.  Hope the band-pass filter is the solution.  Can't wait to install and will report results.  I think the 470/472 problem has been particularly bad here in the Tucson metro area.

I also ordered mine today but more out of curiosity. I love to experiment and this looks like an interesting one.

Cool
« Last Edit: Jan 14th, 2018 at 6:22am by GalinHdz »  

N819PR
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Reply #17 - Jan 14th, 2018 at 7:52am

N214ST   Offline
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I just wanted to suggest a bit of caution on the filter.  I had read a couple of reports that suggested the filter may significantly attenuate the 978 MHz signal in some cases.  That means one could be back to a single frequency ADS-B with no plane-to-plane 978 signal.  You may see improvement in detecting traffic during normal radar coverage, but you may be losing the concept of dual frequency without even knowing it. I also read that unless you are in an area with significant external interference, it may not be that useful as it will also attenuate the 1090 MHz signal a bit just as all filters do. The best solution would be an actual fix of the 472.  Dynon should really take a technical in-depth look at the use of the filter as it may be useful in some locations even after a 472 fix.
 
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Reply #18 - Jan 14th, 2018 at 8:04am

TurboPilot   Offline
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N214ST wrote on Jan 14th, 2018 at 7:52am:
I just wanted to suggest a bit of caution on the filter. 


Caution? This is really not too complicated. Put the filter on and compare your results to a known portable ADSB source. If you don't have one find a friend who does.

In my case I put the filter on and flew it against the Scout running on ForeFlight. In all of my flights so far, the filter equipped 472 out performed the Scout. This was not the case before the filter.

The filter may not work for everyone and may not be the 100% solution for a fully functional 472 ADSB, but in my aircraft things are better. Your results could be different. Why should we be "Cautious"?

The "documentation" on Amazon says it passes the range 980MHz - 1150MHz. Based on what I am seeing it looks the cut off is not that clean letting 978 through. Just a guess.
« Last Edit: Jan 14th, 2018 at 9:06am by TurboPilot »  
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Reply #19 - Jan 15th, 2018 at 8:29am

N214ST   Offline
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TurboPilot - just stating that it is not as simple as "working or not working" in a strategic sense, and that it "is" complicated.  It may be a short-term fix in your case, but it may not be the right solution for everyone.  Again, based on some empirical testing reports I have read, there may be some future downside to using the filter.  If I were in your position and based on your results, I would also use the filter, but in stating caution, I meant we all shouldn't necessarily go out and buy one without understanding potential consequences.  Not faulting you decision at all.  But for example, let's say you are not in an area with significant interference and are experiencing the same 472 issues we all are seeing.  Maybe useful, but intermittent functionality like my system.  Let us again say Dynon comes out with a fix, but a number of people leave the filter installed, but there really  is an issue with an attenuated 980 signal.  At that point, you may be back to a single frequency ADS-B without even knowing.  Just saying in general, quick fixes may have unintended consequences and some caution is always a good thing.  Smiley
« Last Edit: Jan 15th, 2018 at 8:31am by N214ST »  
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Reply #20 - Jan 15th, 2018 at 8:52am

Garrett   Offline
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I think TurboPilot came across the root of problem.(Period) Dynon can work out the details now. There is nothing wrong with filtering out unneeded frequency's and it is logical that the other ADS-B products on Amazon offer the filter or have it built in.  Cool
 
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Reply #21 - Jan 15th, 2018 at 8:53am

krw5927   Offline
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Since they can't fix the problem, Dynon needs to enable industry standard GDL90 receive capability over RS232 on the Skyviews, so we can use another known working ADSB receiver.

Their wholly-owned subsidiary Advanced Flight Systems already does this.
 
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Reply #22 - Jan 15th, 2018 at 11:18am

GalinHdz   Offline
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krw5927 wrote on Jan 15th, 2018 at 8:53am:
Since they can't fix the problem, Dynon needs to enable industry standard GDL90 receive capability over RS232 on the Skyviews, so we can use another known working ADSB receiver.

Their wholly-owned subsidiary Advanced Flight Systems already does this.

Or "partner" with Seattle Avionics and receive ADS-B IN data via WIFI from the MERLIN receiver.

Cool
 

N819PR
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Reply #23 - Jan 15th, 2018 at 5:26pm

Dynon Avionics   Offline
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A few comments: A filter like the one that TurboPilot installed does seem to help with some of the issues that people have experienced, especially around weather reception, but it may not improve the issues around traffic that some of you have reported (although it may for others). Driving this to root cause has been a bit like peeling an onion, where each layer reveals that there's more to peel back. We're hesitant to get into the nitty gritty details, because (1) it's very technical and (2) we're working with external partners on engineering a solution.

There have been multiple times that we thought we were close to "the solution", and then ran into a new issue that forced us to peel back another layer. That said, we're definitely looking into other ways, including some of the suggestions in this thread, as additional mitigations.
 

Please do not use Private Messaging on form to contact. For private support:
Email: support at dynonavionics dot com
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Reply #24 - Jan 15th, 2018 at 5:55pm

TurboPilot   Offline
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Dynon Avionics wrote on Jan 15th, 2018 at 5:26pm:
A few comments: A filter like the one that TurboPilot installed does seem to help with some of the issues that people have experienced, especially around weather reception, but it may not improve the issues around traffic that some of you have reported (although it may for others).


I have made a few more flights and an extended period of watching the screen with the aircraft in the hangar.

"Hangar flying" the aircraft there is absolutely no doubt the 472 with the filter is working better than the 472 without the filter. The 472 with the filter has better reception than my old 470 in the same situation for weather and traffic.

I continue to fly the aircraft with the Scout playing through ForeFlight on an iPhone X. Comparing the 472 to the Scout may be a low bar for comparison but it is a benchmark. Since beginning these tests I have not seen a situation where I was getting less performance from the 472 compared to the Scout. The majority of the time the 472 acquires weather and traffic faster than the Scout.

Of interest, there appears to be a bug with the iPhone X running Foreflight and the Scout. Periodically all traffic disappears with the Scout still connected. Killing the ForeFlight app then restarting it restores the traffic immediately.

So bottom line, so far applying the filter has not impacted any functionality and has definitely improved performance in my aircraft.
« Last Edit: Jan 15th, 2018 at 5:56pm by TurboPilot »  
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Reply #25 - Yesterday at 2:11pm

dlloyd   Offline
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With the 470 receiver I have always experienced traffic dropping off and reappearing.  I thought that was just the nature of things until people began similar complaints with the 472 receiver. I asked Dynon a couple times but was told no one had complained about the 470.  A few posts back someone mentioned a cell phone.  I always forget to turn mine off.  Antenna is with 3' of my pocket with the phone.  Today I flew a short trip with my phone off.  Any displayed traffic was steady, I never saw any unexpected drop.  Correlation?
« Last Edit: Today at 6:54am by dlloyd »  
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Reply #26 - Today at 3:59am

jakej   Offline
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dlloyd,

From my experience it is most likely related.  I know my cell phone affects my autopilot (other brand) & the type of USB charger has an impact too.
Why not ry turning your phone off for a few flights & note the difference in systems performance, if any ?  Wink
 
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Reply #27 - Today at 5:57am

rleffler   Offline
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I'm curious about the cell phone interference.  For those experiencing issues, how far away is your phone from your 472 and antenna?

I flew for the first time this weekend with a 472 and experienced similar issues and I had my cell phone on.  Both my 472 and antenna are about 8' away from the phone.
 
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Reply #28 - Today at 2:18pm

TurboPilot   Offline
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rleffler wrote Today at 5:57am:
I'm curious about the cell phone interference.  For those experiencing issues, how far away is your phone from your 472 and antenna?

I flew for the first time this weekend with a 472 and experienced similar issues and I had my cell phone on.  Both my 472 and antenna are about 8' away from the phone.


Cell phone interference sounds like a reasonable issue, so I did a little experiment. Dialed an ASOS on my iPhone X and placed the iPhone directly on top of my Stratus 2 which was actively connected to an ADSB station and left it there a few minutes. Result - no impact. Stratus continued to receive weather and local traffic.
« Last Edit: Today at 2:21pm by TurboPilot »  
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Reply #29 - Today at 2:34pm

Steve W.   Offline
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TurboPilot wrote Today at 2:18pm:
rleffler wrote Today at 5:57am:
I'm curious about the cell phone interference.  For those experiencing issues, how far away is your phone from your 472 and antenna?

I flew for the first time this weekend with a 472 and experienced similar issues and I had my cell phone on.  Both my 472 and antenna are about 8' away from the phone.


Cell phone interference sounds like a reasonable issue, so I did a little experiment. Dialed an ASOS on my iPhone X and placed the iPhone directly on top of my Stratus 2 which was actively connected to an ADSB station and left it there a few minutes. Result - no impact. Stratus continued to receive weather and local traffic.


I'm not sure what that proved about anything other than THAT Stratus and THAT phone.  It certainly didn't prove anything about the 472 under discussion here...?
 
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