Like you, I also live in a high rise building in an urban location,with lot of Cell/Mobile antenna on roof top of my building, as well as surrounding buildings, I had poor reception of 1090 MHz due to strong RF signals generated by these Cell phone antennas.
I had to add a FA Blue filter between antenna coax and FA Blue Dongle to improve reception. My 1090 MHz reception falls drastically if I remove FA 1090 MHz Blue Cylendrical filter.
Spektrum - How-to Speedily Scan RF Noise in band 24MHz ~ 1800MHz
RF Noise At My Location (24 MHz ~ 1800 MHz)
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