How is the detection range derived?

[Howcome_HFD]

I have set up a basic FR24 installation on a raspberry pi 4B, which works perfectly except for one thing. It automatically defines the detection range at 30nm, but is there some way to extend that setting? I have tried the --max-range setting that is applied at startup but that does not seem to make any difference whatsoever.

Any tips where/what to look for?