Dump1090-mutability: --dcfilter


#1

Hi,

I wonder what --dcfilter is for:

--dcfilter Apply a 1Hz DC filter to input data (requires lots more CPU)

In which case is this useful?


#2

The DC filter is not useful for ADSB due to the encoding being Amplitude encoded. In other radio system it can be quite useful.

The RTL dongles and prostick are actually Software Radios and can be used to listen to other frequencies (from a few MHz to 1.8GHz). The technology used by the RTL dongles is called low IF and zero IF radio conversion. The zero IF conversion will add a DC component to the output that can be filtered out in software. In some radio encoding it is important to remove the DC offset. In ADSB it doesn’t matter.

Leave the DC filter off.


#3

Thank you for the information!