I run an ADS-B receiver at home — it decodes the transponder broadcasts from aircraft overhead, plots them on a live map, and feeds the data to FlightAware. It started life the lazy way: an RTL-SDR dongle plugged into a server indoors, with a run of coax to an antenna. That works, but it’s the wrong topology if you want range, and I wanted to move the whole thing up high and outdoors.

Two things came out of that project worth writing down. First, a diagnostic detour that taught me the map wasn’t lying to me even though it looked like it was. Second — the real content — how to relocate an SDR receiver to the top of a mast without breaking MLAT, which is the part most “just put a Pi outside” guides skip.