I shirked my duties this morning and flew with the Stratux up on my glare shield. As a point of comparison, I have a GDL39 with a dedicated antenna on the bottom of my aircraft back under the RV-8 rear baggage area.
I had no problem getting my iPhone 6P to connect to the Stratux wifi. The first problem came when I tried to get ForeFlight to recognize the Stratux (FreeFlight) device. It took 20 minute of random ideas and then it connected. None of this surprised me since I had the same problem yesterday in my bench. Subsequent boot-ups of the Stratux had no problem with connecting. I'll classify it as one of those random things.
During ground ops and in flight I noticed the ForeFlight "connection" to FreeFlight would drop. This again was random. When I looked closely at the videos linked to the reddit posts I notice it happened to his system as well.
I picked up the first tower at 650' AGL. It was unreliable. I would lose it frequently. The direction and orientation of the aircraft would contribute to the loss. At 2500' AGL I had two towers but that would fluctuate often back to one and zero. By comparison, the GDL39 had five towers. At 3500' AGL I had three towers with the Stratux ranging from 30-50nm while the GDL39 had seven towers from 30-90nm.
I did receive a 4 local radar frames and 1 national radar frame with the Stratux during the test flight. I also received 280 text reports. I checked three local airports and had METAR and/or TAF for each. I don't know the data for the GDL39 but I had radar animations and weather reports for the four airports I checked.
I tested with both a 1/4 antenna tuned to 978 mhz and the little SDR supplied antenna. It's a guess but I think the tuned antenna was better. Both antennas were affected by the orientation of the airplane. I observed a tower 30 miles away while flying toward it and lost that tower when flying away from it.
My initial conclusions are:
- antenna location is important - a tuned belly antenna will likely perform better than my tests
- connectivity is variable - I can't compare with a real Stratus unit and my GDL39 is hard wired to my panel and uses Bluetooth to ForeFlight and Garmin Pilot on the iPhone. (for those who were wondering, "yes", ForeFlight on the iPhone immediately recognized my G3X Touch Connext)
- Reception quality is "OK" - I knew going into the tests that the SDR would not be as discriminating and sensitive as the GDL39. As my altitude increased, the Stratux data improved but the GDL39 was working well at 1000' AGL and when the Stratux was at its best, the GDL39 was still 2x better on towers.
Remember, the Stratux is closest to a first generation Stratus 1.
It was a fun experiment and from that measure, it was a success. However, having flown with a first generation GDL39 for three years now, it's not reasonable to consider them in the same category. If you've got the parts readily available or you enjoy Raspberry Pi projects, it's a fun little project.
I captured lots of notes and screen grabs but since I consider this an educational experience, I'll leave those as "an excessive for the student".