Reddit user BigReid has posted an update on his PCB based hairpin ADS-B filter. He has now added a low noise amplifier (LNA) circuit onto the same PCB board. BigReid used the LNA design written about on this page. The PCB files are here and the Reddit thread can be found here.
Reddit user BigReid has posted on the Reddit rtl-sdr forums his homemade bandpass filter with a pass range of 1-1.2GHz for improving adsb reception. A bandpass filter blocks any interference from signal frequencies outside of the pass range. This might be useful for adsb if you experience a lot of interference from out of band signals at 1090MHz.
His filter is a hairpin filter, which can easily be etched onto a PCB board. You can find the PCB schematic files linked on the post.