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It’s been a crazy three months. CSeries flight testing had me in Wichita almost continously from 21 Sept 2015 until 14 Nov, then home for a weekend, then a week in Montreal for testing in a simulator. The travel finally wrapped up three weeks ago, but I’ve been working long hours since then dealing with all the reviews to finish off the type certification approval program.

I got flying last weekend, and did some more Stratux ADS-B receiver testing, this time with all the bits packaged together into one glob, using plastic tie wraps to hold it all together. The two antennae bases were tie wrapped to the rest of the assembly. I climbed up as high as 9500 ft, but didn’t pick up a single tower. I concluded that the antennae needed a ground plane to work properly.

ADS-B antennae hanging from canopy bowYesterday morning I tried again, this time with the magnetic antennae bases stuck on the steel canopy bow. This wouldn’t be a good place to have them permanently mounted, but it provided a quick way to provide a ground plane. I also tried with them sitting upright on top of the glareshield, but the magnetic bases are useless on aluminum, and they frequently fell over.

 


Picking up ADS-B at 1485 ft ASL (1085 ft AGL)I was amazed to find that I was picking up one ADS-B ground station at low altitude shortly after take-off. I was picking up a station about 65 nm away at 1000 ft above ground! The station was lost as I climbed through about 1500 ft above ground, and reappeared as I descended through about 1200 ft. I repeated the climb and descent three times, and every time the station was picked up at low altitude, but lost when I climbed to 1400 ft AGL. This looks like a classical case of radio ducting, where a significant temperature inversion causes radio waves to bounce between ground and the top of the inversion in a narrow channel - this allows the radio signal to be picked up at low altitude when the transmitter should be well below the horizon.

 


Ottawa airport forecast in ADS-B was 42 hours oldI climbed up to 8500 ft, picking up the station again as I passed through 5000 ft. I then waited until I had received quite a few weather reports, then checked to see what Canadian weather data was received. I found that the ADS-B stream contained weather forecasts for some major Canadian airports, but the data was over 24 hours old. No Canadian airport weather reports were seen. I have concluded that the US ADS-B data, while potentially very useful for flights in the US, is essentially useless for flights in Canada. I will continue to subscribe to XM Weather, despite the $60/month price tag.