Reception at 39,000 ft in 747 Crossing the North Atlantic

Attempted to close a link from aircraft window flying from Washington, DC, to Frankfurt, Germany. Altitude was 36,000 feet.

No luck after maneuvering antenna close to and farther from window - - signal was too weak running no higher than 1 dB SNR with no packets downloaded. When pointed away from correct azimuth, signal levels dropped into minus territory. Two tests on IF Americas over Halifax, NS, and St John, Newfoundland. Then one test on Alphasat over south tip of Ireland.

I believe the problem is signal attenuation through the plastic window. My wife, Susan, thinks I’m nuts :smiling_imp: Ken


Ha! I’m glad you tried it and not me. They would probably lock me in a secret dungeon at Guatemala Bay if I did something like that.


Guatemala bay is possibly not so bad? :smiley:

Haha, my mind was elsewhere.

Correction: Guantanamo Bay

Haha, you guys are funny. Yeah, I was wondering if I would have had the balls. Nice job!

It’s interesting to me, since I still can’t acquire a signal from I4F3 98W, that the materials around you most definitely affect the signal attenuation as much as the noise floor, reflections, and other interference around you.

Perhaps this is because of the band and weakness of signal? Are the signals that easily absorbed?

I was in Oakland yesterday and I received packets by just laying the antenna flat (not recommended); I’m not convinced that it’s your environment. Are you able to see anything in SDR#? How about the other, much more powerful L-band signals?

So the signal is definitely weak. I don’t have the link budget handy, but I seem to recall something like -140 dBm. If you are in the city tomorrow, maybe we can test your gear against the demos that I have with me.

Nicely done. Likely more to do with azimuth and elevation vs the plastic window. I use an enclosed waterproof plastic enclosure and I get great reception.

At leased you would have Outernet :wink: to keep up on current affairs …

You shouldn’t use radio receivers inside a commercial aircraft. They contain local oscillators which can radiate quite a bit and interfere with aircraft comms systems. So the restriction to use wireless equipment also applies to receivers.

Direct conversion receivers that only work at audio frequency (say, by rectification of RF) do not have this issue, so they shouldn’t cause problems, but they also frowned upon usually.

i read in the “Tech” page of the outernet web page this " Outernet L-Band hardware can also be used for Inmarsat reception, including SafetyNET, EGC, and AERO."
and i want know HOW the commercial flight do for reading info from the same sattelite ?