At our regional airport, we have observed that 1090Mhz reception is very poor for nearby airplanes. Once they go below 1000ft AGL, signal is all but lost. We run dump1090-mutability on Raspbian without special tuning for gain. We have tested with the standard FlightAware dongles and both whip and outdoor antennas and various cable lengths, with identical results.
Moreover, running dump1090 inside an airplane, it’s next to impossible to see the messages it broadcasts.
Can you please advise what might cause this and what possible workarounds exist? We are mostly interested in ADS-B from around the airport’s traffic pattern and up to 25NM below 5000ft.