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« on: October 19, 2015, 11:22:29 am »
On Sunday a friend and I tried some ground and airborne tests with mixed results. The recent State of the Nation post makes this less relevant but may be useful and some may have useful observations to make.
The units were in use but only normally two at a time.
Unit A my first effort which is soldered and has no baro
Unit B with Jeremy's ARF shield with baro
Unit C with Jeremy's ARF shield with baro running on Pi B model (A & B on Pi B+)
All three units currently get GPS fix from tablets whilst that slow boar makes its way from China.
Unit A has two GSM style aerials as some have recommended on here. They are close together on one end of the case.
Unit B has the standard aerials the components come with as does unit C.
Experiences
After a quick verification of P3i signals being seen on units A and C we go airborn. Unit C generally saw the P3i traffic info 3-5 miles away and Skydemon gave good interpretation of collision risk when appropriate. i.e. red aircraft graphic and heading line and warning message with range. As you will hear I haven't seen this! but Paul unfortunately couldn't take a screen shot.
Disappointingly, unit A only showed the P3i when flying in very loose formation! something like 100 feet. I then swapped over to unit B and we achieved pretty much the same results. Paul commented that unit C gave him good warning about a collision and was looking for some time before becoming visual in slightly hazy conditions (we were flying at approx 100 kts with me orbiting). There was some impact on range depending on direction with better range if I was flying toward unit C. Both units were on the coaming with a possibility of blanking by the compass. Unit A & B were in an RV8 and unit C in a Bulldog.
We went back to using units A and C and repeated the exercises with similar results. After landing we placed unti B and C in the Bulldog and walked away with unit A. Unit A lost unit C again at 100 ft but we got more like 700 ft on unit B. it also seemed that the two GSM like aerials were interacting with one blanking the other if it was in line.
One suspicion was power in the Bulldog but checking the voltage on the GPIO pins it was 4.90 and 3.3 respectively. However this was through a cigarette style adapter running a tablet and the PAW although it says it can provide 2.1A to both sockets. I would like to try a power pack like is used on units A & B in the future.
We then set up the final test with unit B in the Bulldog and unit A using the taller standard aerial on the P3i part. We got similar result again.
We got excellent range on ADSB traffic but mixed results on P3i, one aircraft getting a useful warning range but not the other.
For the future we will be adding the onboard GPS and trying a battery pack (we I know works) to eliminate that as a factor. Any other thoughts appreciated.
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