1090MHz Filter for ADSB 472 Issues?

[turbopilot]

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=UTF8&psc=1


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.

 

[Garrett]

I just ordered one

 

[turbopilot]

I just ordered one 

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=UTF8&psc=1


https://www.amazon.com/gp/product/B00CVQJRUA/ref=oh_aui_detailpage_o06_s00?ie=UTF8&psc=1

 

[Garrett]

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

 

[swatson999]

I just ordered one 

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=UTF8&psc=1


https://www.amazon.com/gp/product/B00CVQJRUA/ref=oh_aui_detailpage_o06_s00?ie=UTF8&psc=1

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...

 

[jakej]

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.

 

[turbopilot]

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.

 

[Garrett]

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.

 

[turbopilot]

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.

 

[Garrett]

The original 470 great, maybe it had a better designed tuning circuitry.

 

[swatson999]

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.

 

[Garrett]

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.

 

[turbopilot]

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.

 

[alexe]

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

 

[turbopilot]

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.

 

[dwightsmall]

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.

 

[GalinHdz]

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.

 

[mrdaud]

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.

 

[turbopilot]

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.

 

[mrdaud]

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.