FlightAware Discussions

Signal Strength Jump, Gain Settings Unchanged

Hi all,

I noticed recently that a couple days ago, I got a jump in signal strength logged in graphs that looks like I upped the gain, but I have not. ‘systemctl status dump1090-fa’ shows the correct gain setting as well as the gain set in my configuration file. However, if you look at the graph, you can clearly see a jump sometime on Wednesday in signal strength as well as the number of messages >-3dbfs. I have not touched the pi at all, no reboots or configuration changes. The upgrade to 3.7.1 was done weeks ago, and uptime showed as almost a month. I just rebooted the pi, but it did not revert to the old signal strength. Does anyone have any ideas as to what might have happened? I have not yet physically checked on the pi and antenna, will update if I find anything out of the ordinary.

57%20AM

That’s unusual.

I don’t suppose you are using a gain of -10?

If anything i’d suspect the lower signal level was the anomaly and it somehow corrected itself.
Do you have a longer term graph?

My gain is set to 35. I went to the pi and antenna today, didn’t see anything wrong, but jiggled all the connections. It seemed to work:

33%20PM

What a weird issue.

That actually means your connection is bad.
But if it works for you then that’s fine i guess.

Also your normal gain setting seems really low, but just the same if it works for you :slight_smile:

Update: So the issue kept coming back, no matter how much I changed tightened/loosened the connections. I finally traced it back to a problem with my SDR (ProStick) dongle. I had dropped it a while back and its case had popped off but I didn’t think I had damaged it, and it still worked.

I’m not sure exactly what I broke, but the symptoms were quite bizarre. Even when the signal strengths jumped up, I was not getting any additional messages, or aircraft tracked. Turning up the gain produced expected effects on messages and range, but signal strength would not change. Even at max gain, the percentage of messages >-3dBFS with the broken dongle never surpassed .1%, but I would still see the effects of high gain, i.e. messages from close planes overloading the receiver.

With the new dongle, I am able to produce roughly the same range with a much lower gain as expected. Also, the dynamic range seems to have improved and I can now receive close aircraft without overloading the receiver.

@wiedehopf Thanks for the help and the super helpful graphs. Without them I may not even have realized there was an issue originally. I have finally have a stable signal strength now.


28%20PM

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