Dear all, what is the easiest way to figure out the correct amount of gain. My setup is:
raspi3 with flightaware 7.2 image.=> the orange dongle (R820T2 SDR + RF Amp v1.1) => ADS-B SAW filtered preamp 1090 MHz => 6 meters (19,6 ft) cable => ADS-B 1090 antenna.
piaware-config:
rtlsdr-device-index 0
rtlsdr-gain 49,6
rtlsdr-ppm 0
Thanks a lot!
Marcus
I would start with installing Graphs1090:
Let it running for 24 hrs and see what the percentage of strong messages is.
If it is higher then 5% reduce the gain.
Sometimes it can’t be lowered due to environment circumstances but that is totally dependant on your local environment.
Max gain for the orange dongle is indeed 49,6.
There is some code around that will periodically check the gain level and adjust it for you. Look around for autogain1090 on GitHub. I have been running it for a while but I’d have to check my notes to see how it is installed. It runs each afternoon and checks the percentage of messages that are over -3dB.
You might want to have a read of this thread: Thoughts on optimizing gain
It’s long, but has a lot of discussion about gain and various ways to measure your receivers performance.
First question: What is YOUR major interest (it makes a difference to the “best” gain setting).
You may be interested in:
Without explaining why, raising your gain to maximise range usually results in close aircraft overloading the receiver causing distorted/un-decodable messages.
Dropping the gain so you don’t lose local positions will usually cost you max. range.
It’s your station, so you get to optimise it to suit your interests.
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