How to verify strong messages

FlightAware General
1

Dear all,

I’m having difficulties verify strong messages since some time now. Usually I use the command

awk “$(cat /run/dump1090*/stats.json| grep total | sed ‘s/.accepted":[([0-9]).strong_signals":([0-9]).*/BEGIN {printf “\nPercentage of strong messages: %.3f \n” , \2 * 100 / \1}/’)”

I cannot recall who actually created that command. Anyway it was said that the output value should around 5 percent, and therefor you should adjust the gain in dump1090-fa.
Currently on those stations the output is 0 even though the stations are online and feeding.

I have three and the two I’m talking about are: 227543 and 240423

Any suggestions?

Thanks, Marcus

Any idea?

2

Note the correct command is:

awk "$(cat /run/dump1090*/stats.json| grep total | sed 's/.*accepted":\[\([0-9]*\).*strong_signals":\([0-9]*\).*/BEGIN {printf "\\nPercentage of strong messages: %.3f \\n" , \2 * 100 \/ \1}/')"
3

Thanks @chrislfa but the output is still 0

4

Someone else may be able to comment on that. Perhaps these sites are not producing strong signals and so 0 is correct.

You may find this article I wrote useful, it links to a FlightAware blog post with a nice way to find an optimal gain setting. You need to know the RSSI range of your SDR stick. For the blue Pro Stick Plus that is given in the blog post.

I find this ‘filling the range’ approach works more reliably and quickly than the finger-in-the-air 5% or any other approach, but in fairness the 5% strong messages is a good proxy for an optimal gain when the site is receiving a lot of strong signals.

5

I had values around five until yesterday. That is strange to me and that is why I’m asking.

I just did a complete reinstall of my test setup with no change…

6

Oh right, that does seem a bit odd. Did both stations have values around 5 and then both stations have gone to 0 at the same time?

7

yes both. The test station was set up this morning and never had anything else than 0

8

How do I find out that value. Skyview doesn’t work anymore…

9

What do you mean by it doesn’t work any more? Are you no longer seeing aircraft on the map and entries in the table, or does it fail to load or something else? Your stats page shows both of those sites are feeding numbers to FA now. You can select columns using the button in SkyAware and tick RSSI.

Try viewing the stats file without the line processing and see if you can access it and have numbers showing for things like strong_signals. Note no need to post the line here, just for you to eyeball and check.

cat /run/dump1090*/stats.json| grep total
10

For station 240423, “cat /run/dump1090*/stats.json| grep total” will give me:

“total”:{“start”:1737034509.6,“end”:1737044049.7,“local”:{“samples_processed”:22863282176,“samples_dropped”:0,“modeac”:0,“modes”:194597520,“bad”:450217596,“unknown_icao”:80619883,“accepted”:[29185,3245],“signal”:-24.2,“noise”:-36.5,“peak_signal”:-10.9,“strong_signals”:0,“gain_db”:49.6},“remote”:{“modeac”:0,“modes”:0,“bad”:0,“unknown_icao”:0,“accepted”:[0,0]},“cpr”:{“surface”:0,“airborne”:2515,“global_ok”:2184,“global_bad”:0,“global_range”:0,“global_speed”:0,“global_skipped”:0,“local_ok”:192,“local_aircraft_relative”:0,“local_receiver_relative”:0,“local_skipped”:139,“local_range”:0,“local_speed”:0,“filtered”:0},“altitude_suppressed”:0,“cpu”:{“demod”:929982,“reader”:181001,“background”:26572},“tracks”:{“all”:547,“single_message”:466,“unreliable”:478},“messages”:32430,“messages_by_df”:[3350,0,0,0,5856,1991,0,0,0,0,0,7537,0,0,0,0,193,6975,256,0,5025,1247,0,0,0,0,0,0,0,0,0,0],“adaptive”:{“gain_db”:49.6,“dynamic_range_limit_db”:49.6,“gain_changes”:5,“loud_undecoded”:0,“loud_decoded”:0,“noise_dbfs”:-38.9,“gain_seconds”:[[49.6,9497],[58.6,29]]}}

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11

Maybe @wiedehopf can deliver some input.

You put the question in “General” category, so maybe not many experts see it.
Would fit better to this category

Latest FlightAware/ADS-B Flight Tracking topics - FlightAware Discussions

Maybe a Mod can move it.

12

I took the posted text, changed the pasted “ for " and ran it through the sed command. It failed due to wrong brackets. I removed the extra gain_db section (compared to my own json) and got the same result. That’s not the same as getting 0 and I don’t know enough about what data is expected in the json and wiedehopf’s choice of command to advise further.