Suddenly not seeing many planes at all

FlightAware ADS-B Flight Tracking
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Hi all,
Running Piaware4 with both piaware and FR24 feeders on a Raspberry Pi3.

Just before Christmas, I ran an update on the Pi and things went bad - it wouldn’t boot, so I had to re-image and start from scratch. I reestablished the same FR24 and piaware feeds and the Pi is now feeding again.

However, I’ve noticed that it’s hardly picking up any flights. (I did think that maybe there aren’t any, but when I check on the FA website, there are a fair few around me, but my Pi is no longer picking them up. I’ve also noticed that my max range seems to have dropped from about 85 miles to 8 or 9.
Nearest airport is probably LPL (although MAN is equally close).

So I’m thinking maybe 2 things:

  1. Something’s gone wrong on the re-install (although not sure what would cause this)
  2. Something’s gone wrong with the FA Pro stick.

Antenna hasn’t moved at all - it’s in my loft, right at the top, no changes to the connector or cable.

Is there anything I can do to diagnose this before starting to pull it tp pieces and start again?

Thanks.
Matt

1 Like
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graphs can be useful to get a better picture:

GitHub - wiedehopf/graphs1090: Graphs for readsb / dump1090-fa / dump1090 (based on dump1090-tools by mutability)

Given that you probably re-imaged the card, try re-plugging the SDR, re-doing the SMA at the SDR and re-plug the power for the pi.

You can check if there are voltage issues:

sudo dmesg --ctime | grep voltage

No output means no issues.

2 Likes
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Thanks, @wiedehopf - no output from the voltage check, so all’s good there.
I was just reading about the graphs, so good timing. I’ll get them instlled now and see what is produced and will come back.

Thanks.

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While I wait for the graphs to collect sufficient information, I just had a thought that it could be the gain setting, so I changed this to max. Now I see a couple more aircraft, but they only appear for about 10 miles radius, then they disappear.

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That points to either moisture in the coax or a bad connection.

Did you re-do the SMA connection at the SDR, check if the pin is straight and present?

When you ran the update, did you by chance move the Pi or bring other electronics up there?

1 Like
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No, I’ve not even undone the SMA - it’s been attached to the antenna and the ProStick all the time. It’s up in the loft, so shouldn’t be getting any moisture.

A total fresh install (wipe the SD and start from scratch) seems to have made a bit of a difference, as I just had a couple of aircraft at about 20 miles out. Looking on the FA site, there’s next to nothing about now anyway, so I’ll come back when it’s a bit busier and see what it’s tracking. Meanwhile, the graphs are installed and should be tracking some data…

Thanks - will come back shortly…
Matt

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OK, update… I’ve totally refreshed (re-imaged the card, reinstalled, etc.) and left it running with the graphs collecting information for a couple of weeks. I’ve noticed that the maximum range over the last 7 days, for example, is 27.9 nautical miles, whereas previously it used to be a maximum of 70, 80 or even 90 miles.
I’m beginning to wonder if this has something to do with the FA Pro Stick being faulty? Is there any way to check that?
I can send screenshots of my graphs if you let me know which ones are useful for diagnosing.

Thanks.
Matt

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For that kind of partial fault … not really.
Only test is get a new one and compare.

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I thought that might be the answer :slight_smile: I’ll have a look around and see what’s out there. If it is faulty, it should still be under warranty as I only bought it in May, so let’s see.

Thanks.
Matt

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High ambient RF noise near 1090 MHz can severely reduce range. Could there be a sudden elevation?

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I’ve resolved it. Turns out that the Pro Stick was the issue. Bought another and put it in and straight away, I’m straight back up to seeing aircraft from 80-90 miles, which was what it used to be.
Now, to see if I can get a return on the original, this could be interesting…

Thanks for your help!
Matt

1 Like
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Spot where I put the replacement Pro Stick in!

Graphs2
Graphs21190×1683 376 KB

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I am having the same problem. The FA recommended equipment was purchased and quite a bit of time spent to achieve a high degree of performance. The site was working well, seeing planes out to 200+ miles. Then about a year ago everything stopped working. A few months ago, on it’s own, it started working again. ??? At this time the site was ranked in the 800 range. Now it appears, the Pro Stick needs replacement as it is now ranked in the 7000 range and only seeing planes a few miles away. Enough in purchased equipment and troubleshooting efforts. I’m pretty much done with FA at this point.

Larry

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Hardware is fickle. What troubleshooting did you do? (Since this is your first post, I assume you did not post here at the time that you were having trouble, which is unfortunate)

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I just ran onto a similar problem apparently last night, but didn’t notice it until I checked it from the office.

Weather: I did not notice any glaringly obvious meteorological events early this morning that could cause water or ice to form in the feedlines or antenna hardware, or wick into the amplifier and short it out. Humidity was still dry but temperature reached 4 degrees C, while not the first time this autumn. The night was still Clear and Visibility Unlimited VFR conditions from the surface to the edge of space when left for work.
On Wednesday we had a very dry afternoon with high winds and blowing dust, but Thursday night and morning was dead calm.

We have not had a true hard freeze yet, but the nearest weekend before Halloween is normally when I plug in all the heat trace tapes and make sure all the winterizing is done.

Looking at historical data accessible from the office, I saw aircraft counts drop dramatically starting at the 5 AM to 6 AM hour versus the same hour on the same dates.

Thurs Oct 28 2921	Fri Oct 29 2021
Hour	Posit	Airc	Hour	Posit	Airc
00	6431	43	00	4970	67
01	2695	27	01	5494	36
02	2703	29	02	5431	39
03	3522	25	03	2713	39
04	6606	39	04	4649	43
05	2977	33	05	3615	25
06	3597	56	06	370	8
07	13695	139	07	239	2
08	46338	218	08	240	5
09	51262	248	09	584	6
10	50875	268	10	939	7
11	56806	277	11	159	2
12	54967	284
13	58279	293
14	57417	306
15	53195	269
16	49435	264
17	42611	244
18	40371	203
19	31421	179
20	32023	189
21	21725	189
22	13551	164
23	9526	120

Here is the trailing 24 hour and most recent ADS-B and UAT chart.
ADS_B_20211029

Speculations - maybe the pre-amplifier died at about 5:15 AM this morning. Maybe the T circuit output to power the amplifier died. However, the UAT position count AND the ADSB position count have been exactly the same over the past 5 to 6 hours. While I have encountered a handful of aircraft tracks that are broadcasting UAT and ADS-B, they are usually fairly rare.

Possible troubleshooting tonight:
I have two new runs of LMR-240 cable with proper SMA male ends for the RTL-SDR dongle female connectors. The antennas are not at DC ground so the amplifier can be removed entirely from the circuit. With it gone, there should still be about 50% of the aircraft I used to see with it inserted into the system. If that fails, I do have a spare RTL-SDR dongle although it still has the default serial number, as opposed to the pair with 1090 and 978 as serial numbers. It can be re-programmed on the spare Linux box.

Another possibility could be something happened to the antenna. Birds have destroyed other antennas in the past, but I didn’t check that before heading for work because it was pitch black and I was unaware there was a problem with the feeder until I got to work. Worst case, I have other components from a second feeder I was building to set up in a very remote dead zone once a site was acquired (probably somewhere in western Irion County or southeastern Reagan County).

I will let everyone know what I discover once the fault is isolated.

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The problem turned out to be the RTL-SDR dongle itself.
The coaxial cable tested out OK. Removing the LNA did not improve any reception, and soon other possible faults were eliminated all the way to the actual dongle.
Reprogramming a spare dongle and swapping it in brought back all but the weakest signals around the outskirts of Ft Worth and El Paso, Amarillo to San Antonio, and those deep in Mexican airspace.

Once the winterizing is complete, I’ll change out the RG8x feedline for the LMR-240 which has half the dB / 100 foot loss at 1090 mhz. (source: https://www.w4rp.com/ref/coax.html ) That is when the 978 mhz antenna and feedline will get upgraded.

Allegedly there is a filtered LNA for 978 someone makes and sells, but I suspect the entire world’s inventory is in a freight container buried deep in a ship a hundred miles off the coast of California that won’t get to the front of the line to be unloaded until Easter 2023.

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