Many thanks to SWLing Post contributor, Ivan Cholakov (NO2CW), who writes:
Last week I took an Eton Satellit with me on a flight from Tampa, Florida to Washington DC. The radio is very light, portable and packed with features. I have used an SDR radio before for inlight FM reception where I recorded audio, but this time I decided to only count stations with an RDS lock. With so many signals battling RDS is tricky to catch as every 10 seconds or so one station comes on top of another. The flight was just short of 2 hours and I divided my logs into three 30 minute segments. Not suprisingly looking into the technicalities I noticed RDS is commonly received from stations 50 -100 kW of power and tall towers.
Interestingly signals seem to be stronger a lower altitudes. My theory is that FM broadcast antennas heavily favor gain on the horizontal plane parallel to the terrain and send as little signal as possible out into space. I overlaid my logs onto three maps and also a video:
Impressive Ivan! I’m taking a flight later this month and might even try this with the FM radio built into my Moto G6 smart phone which also includes RDS (although I doubt reception can match that of the Satellit.
This is fascinating, Ivan! Thank you for sharing.